TREATISE   ON 
GENERAL   AND    INDUSTRIAL 

ORGANIC    CHEMISTRY 


TREATISE    ON 
GENERAL  AND  INDUSTRIAL 

ORGANIC   CHEMISTRY 


BY 

DR.   ETTORE    MOLINARI 

PROFESSOR    OF    INDUSTRIAL    CHEMISTRY    AT    THE     ROYAL    MILAN     POLYTECHNIC 
AND    AT    THE    LUIGI    BOCCONI    COMMERCIAL    UNIVERSITY 


TRANSLATED    FROM   THE   THIRD    ENLARGED    AND    REVISED    ITALIAN 

EDITION    BY 

THOMAS  H.  POPE,   B.Sc.,  •  A.C.G.I.,  F.I.C. 


PART   I 

WITH    254    ILLUSTRATIONS 


PHILADELPHIA 

P.    BLAKISTON'S    SON   &   CO. 

10 1 2    WALNUT   STREET 

1921 


Printed  in   Great  Britain. 


TRANSLATOR'S   PREFACE 

IN  this  translation  it  has  been  deemed  undesirable  in  most  cases  to 
convert  the  metric  weights  and  measures  into  those  of  the  English  system, 
but,  in  general,  prices  are  given  in  British  currency,  twenty-five  lire  being 
taken  as  the  equivalent  of  one  pound  sterling.  Where  quantities  are  given 
in  tons,  the  latter  are  to  be  read  as  metric  tons  of  1000  kilograms  or 
2204' 6  Ib.  avoirdupois. 

The  abbreviations  employed  for  the  different  units  of  weights  and  measures 
are  those  in  common  use,  and  temperatures  are  expressed  in  degrees  Centigrade 
in  all  cases. 

THOMAS  H.  POPE. 


457665 


PREFACE   TO   THE   THIRD    ITALIAN   EDITION 

THE  second  edition  of  this  treatise,  which  appeared  in  1913,  has  been 
exhausted  for  over  two  years,  while  the  Spanish  and  English  versions  have 
also  been  completely  sold.  The  publication  of  this  new  edition  has  been 
delayed  owing  to  the  vicissitudes  of  the  war,  which,  although  apparently 
at  an  end,  has  left  industrial,  commercial  and  social  upheaval  behind  it.  The 
most  serious  and  urgent  problem  now  preoccupying  all  so-called  civilised 
countries  is  that  of  production,  which  should  lead  to  the  rapid  recovery  of 
the  wealth  and  reserves  destroyed  by  the  monstrous  conflict  which  sacrificed, 
on  the  altar  of  international  imperialism,  upwards  of  fifteen  millions  of  human 
lives. 

A  clamant  need  is  the  speedy  transformation  of  the  improvised  and  super- 
fluous industries  of  war  into  peace  industries.  Never  before  have  the  interests 
of  humanity  imposed  such  serious  tasks  on  the  technologist,  particularly  on 
the  chemist. 

The  aid  of  science  is  necessary  in  order  to  arrive,  as  rapidly  and  economically 
as  possible,  at  the  most  intense  production  of  the  materials  furnished  by  nature 
and  consumed  by  society.  This  is  necessary  in  the  interests  of  all,  since, 
even  when  the  legitimate  restlessness  of  nations  sacrificed  by  the  dominating 
castes  shall  have  resulted  in  a  new  social  order,  less  barbarous,  less  chaotic 
and  less  unjust  than  that  now  in  force,  increased  output  will  be  more  than 
ever  of  importance  for  the  welfare  of  the  new  humanity. 

In  this  edition,  from  which  new  English,  French  and  Spanish  editions 
are  being  prepared,  account  is  taken  of  the  industrial  progress  in  the  various 
branches  of  chemistry  and  of  statistical  data  up  to  the  end  of  the  year  1913. 

For  the  period  of  the  war,  only  data  referring  to  Italy  can  be  guaranteed. 
The  statistics  and  prices  for  the  years  of  war  are  of  transitory  importance 
and  are  recorded  as  curiosities  reflecting  the  abnormalities  of  this  historic 
period.  Fiscal  tariffs  cannot  be  given,  since  in  all  countries  these  have  under- 
gone change  and  will  not  be.  systematised  for  some  time  yet. 

THE  AUTHOR. 

MILAN. 


VI 


A  NEW  treatise  on  Organic  Chemistry  might,  in  view  of  the  existence  of  the 
excellent  works  of  Bernthsen  and  Holleman,  be  considered  superfluous. 

Both  of  these  books,  which  differ  little  in  the  manner  in  which  the  subject 
is  developed,  are,  however,  confined  to  a  theoretical  and  systematic  exposition 
of  the  many  organic  compounds,  the  industrial  side  of  the  question  and  the 
applications  of  these  compounds  being  almost  entirely  neglected.  It  is  hence 
difficult  for  the  student  to  ascertain  which  of  the  thousands  of  substances 
described  are  really  of  practical  importance. 

Modern  teaching  of  chemistry  adheres  in  a  too  one-sided  manner  to  the 
old  but  fruitful  idea  of  Liebig,  that  "  to  obtain  a  sound  practical  man  it  is 
necessary  to  train  a  good  theorist."  This  conception  was  taken  too  literally, 
although  it  gave  good  results  when  chemical  industry  was  in  its  infancy, 
since  in  those  days  any  theorist  could  easily  introduce  new  and  important 
methods.  But  to-day,  when  the  industry  has  attained  the  adult  stage — has 
advanced  to  such  an  extent  and  become  so  varied  and  complex,  being  stimulated 
incessantly  by  keen  national  and  international  competition,  which  demands 
rapid  changes  and  improvements — the  valuable  time  of  the  young  technician 
cannot  be  wasted  in  a  protracted  and  sometimes  sterile  apprenticeship. 
Present-day  conditions  require,  therefore,  some  such  expansion  of  Liebig's 
maxim  as  the  following  :  In  order  to  produce,  rapidly  and  with  increased 
certainty,  a  sound,  practical  man,  it  is  necessary  to  train  a  good  theorist  and 
to  initiate  him  into  both  the  theoretical  and  the  practical  study  of  the  more 
salient  industrial  problems. 

It  does  not  suffice  that  the  young  chemist,  about  to  begin  his  industrial 
or  teaching  career,  should  have  a  thorough  knowledge,  for  instance,  of  the 
various  syntheses  and  constitutional  formulae  of  the  sugars.  He  should  also 
be  acquainted  with  at  least  the  general  outlines  of  the  industrial  processes 
and  of  the  technique  of  the  manufacture  of  sugar,  beginning  with  the  slicing  of 
the  beets  and  proceeding  to  the  exhaustion  of  the  pulp,  defecation,  saturation, 
filtration  with  filter-presses,  boiling,  and  vacuum  concentration  in  multiple- 
effect  apparatus,  refilling  and  centrifugation  of  sugar  crystals,  utilisation  of 
residues,  and  so  on.  He  should,  indeed,  understand  the  plant  and  chemical 
processes  of  the  more  important  industries,  as  these  often  find  application  in 
the  manufacture  of  products  of  a  secondary  or  entirely  new  character. 

What  would  avail  a  study  of  the  wonderful  artificial  colouring-matters 
derived  from  coal-tar,  with  the  inexhaustible  syntheses  composing  their  theo- 
retical basis,  if  it  were  limited  to  a  simple  mnemonic  exercise  for  the  student 
and  no  notice  were  taken  of  the  interesting  practical  applications  to  the  dyeing 
of  the  various  textile  fibres  ? 

Nor  should  the  young  student  ignore  statistics  of  production;  he  should 
be  able  to  appreciate  the  importance  of  variations  in  the  exportation  and 
importation  of  the  principal  chemical  products,  and  to  judge  of  the  economic 
and  social  conditions  with  which  such  variations  correspond. 

After  a  brief  novitiate,  he  should  be  in  a  position  to  point  out  the  more 


viii  PREFACE   TO   THE   FIRST   ITALIAN   EDITION 

striking  technical  defects  and  the  more  marked  difficulties  met  with  in  par- 
ticular industrial  processes  and  to  suggest  rational  and  not  fanciful  remedies. 

It  is  this  space,  the  vacant  region  representing  a  suitable  fusion  of  theo- 
retical with  applied  chemistry,  which  requires  filling.  This  I  have  attempted 
in  the  present  work,  which  of  itself  is  certainly  insufficient  to  cover  the  whole 
of  the  ground. 

The  difficulties  encountered  in  preparing  the  volume  on  Inorganic 
Chemistry  are  multiplied  in  dealing  with  Organic  Chemistry,  and  this  is  the 
case  as  regards  the  collection  and  confirmation,  not  only  of  the  statistical 
data  but  of  the  chemical  processes  giving  the  best  results  in  practice.  For 
in  any  particular  industry  it  has  often  been  found  that  the  results  of  investi- 
gations are  in  such  disaccord  with  the  practical  data  as  to  render  it  a  matter 
of  great  uncertainty  what  conclusions  should  be  presented  to  the  reader. 

Inquiries  addressed  to  manufacturers  resulted  in  aggravation  of  this 
uncertainty,  what  was  confirmed  on  the  one  hand  being  denied  on  the  other, 
and  plant  guaranteed  by  one  firm  to  be  the  best  being  decried  by  a  competing 
firm.  It  hence  became  necessary  to  apply  directly  to  the  operatives- working 
a  given  process  and  to  draw  conclusions  from  the  whole  of  the  data  and 
information  thus  obtained. 

It  is  thus  that  readers  may  explain  the  contradictions  between  different 
authorities  on  one  and  the  same  subject,  and  also  the  fact  that  the  conclusions 
reached  by  the  author  with  reference  to  certain  industrial  processes  are  not 
always  in  accord  with  those  given  in  other  treatises. 

The  intention  has  certainly  not  been  to  prepare  a  complete  treatise  on 
technological  chemistry  and  still  less  on  chemical  technology.  The  work 
having  to  be  restricted  within  limits  of  space  approximating  to  those  of  vol.  i, 
the  author  has  descended  to  details  only  with  some  of  the  principal  industries 
and  especially  with  those  best  adapted  to  give  a  general  idea  of  the  different 
applications  of  chemical  processes  and  of  chemical  technics. 

To  this  end  the  author  has  dwelt  preferably  on  the  industries  of  illumin- 
ating gas,  sugar,  alcohol,  beer,  acetic  acid,  dyeing,  textile  fibres,  fats  and 
soaps,  explosives,  etc. 

From  these  examples  the  student  may  gather  much  instruction  applicable 
to  many  other  industries  not  dealt  with  in  detail. 

Repetition  has  been  avoided  and  time  and  space  saved  by  frequent  refer- 
ences to  arguments  already  developed  in  vol.  i,  Inorganic  Chemistry. 

Advice  and  collaboration  are  desired  from  readers  and  colleagues  in  order 
that  gaps  in  the  present  work  may  be  filled  and  inaccuracies  and  defects 
remedied. 

E.  MOLINARI. 

MILAN. 


CONTENTS 

PAGE 

TRANSLATOR'S   PREFACE         .  v 

PREFACE  TO  THE  THIRD  ITALIAN  EDITION. vi 

PREFACE  TO  THE  FIRST  ITALIAN  EDITION vii 

PART   I.     GENERAL 

PURIFICATION  OF  ORGANIC  COMPOUNDS 2 

Crystallisation,  2 ;  sublimation,  boiling-point,  fractional  distillation,  2 ; 
rectification,  3;  melting-point,  5;  specific  gravity,  7. 

ANALYSIS  OF  ORGANIC  COMPOUNDS 7 

Qualitative  composition,  7 ;  quantitative  estimation :  of  carbon  and 
hydrogen,  8;  of  nitrogen,  10;  of  halogens,  12;  of-  sulphur  and  phosphorus,  13. 

CALCULATION  OF  EMPIRICAL  FORMULA 13 

DETERMINATION  OF  MOLECULAR  WEIGHT  BY  CHEMICAL  MEANS     .       14 
POLYMERISM         .  14 

VALENCY  OF  CARBON,  CONSTITUTIONAL  FORMULA,  ISOMERISM        .       15 

Theory  of  radicals  and  types,  15;  structural  formulae,  17;  rational 
formulae,  18. 

METAMERISM,   PSEUDOISOMERISM,   TAUTOMERISM,    DESMOTROPY    .       18 

STEREOISOMERISM  OR  SPACE  ISOMERISM       ......       19 

Stereoisomerism  in  derivatives  with  doubly  linked  carbon  (alloisomerism) 
21 ;  stereoisomerism  of  nitrogen,  22 ;  separation  and"  transformation  of 
stereoisomerides,  23. 

HOMOLOGY  AND  ISOLOGY  . 24 

PHYSICAL  PROPERTIES  OF   ORGANIC  COMPOUNDS  IN  RELATION  TO 

THE  CHEMICAL  COMPOSITION  AND  CONSTITUTION          ...       24 

Crystalline  form,  24;  solubility,  25;  specific  gravity,  25;  molecular  volume, 
25 ;  melting-point,  25 ;  boiling-point,  25 ;  heat  of  combustion  and  of  formation, 
25 ;  heat  of  neutralisation,  26.  Optical  Properties  :  colour  26 ;  refraction,  27 ; 
influence  on  polarised  ligh^,  27;  magnetic  rotatory  power,  28.  Electrical 
conductivity,  29. 

CLASSIFICATION  OF  ORGANIC  COMPOUNDS 29 

OFFICIAL  NOMENCLATURE 29 

PART  II.    DERIVATIVES   OF   METHANE 
AA.    HYDROCARBONS 

(a)  SATURATED  HYDROCARBONS        . 31 

Natural  formation  and  general  methods  of  preparation,  31 ;  table  of  saturated 
hydrocarbons,  32;  Methane,  33;  properties,  preparation,  fire-damp,  deton- 
ating mixtures,  industrial  preparation,  34-36;  Ethane,  36;  Propane,  36; 
Butanes,  37;  Pentanes,  37;  Hexanes,  37;  Higher  Hydrocarbons,  37. 

ix 


x  CONTENTS 

PAGE 

Illuminating  Gas  :  history,  38;  components,  40;  retorts,  41;  furnaces,  45; 
purification,  45;  hydraulic  main,  45;  naphthalene  separators,  46;  separation 
of  ammonia,  47 ;  scrubbers,  48 ;  separation  of  sulphur  compounds  and  cyanogen 
compounds,  49;  exhausters,  53;  pressure  regulators,  53;  gasometers,  54; 
pressure  regulators  for  consumers,  55;  transport  to  a  distance,  56;  gas-meters, 
56;  yield,  value  and  price,  58;  statistics,  59;  physical  and  chemical  testing 
of  gas,  60;  illuminating  power,  62;  comparison  between  various  sources  of 
light,  64;  oil-gas,  64. 

Petroleum  Industry  :  history,  localities  of  production,  65 ;  orig'n  of  petroleum, 
67 ;  fishing  industry,  69 ;  composition  and  properties  of  crude  petroleum,  70 ; 
extraction  and  industrial  treatment,  73 ;  distillation,  75 ;  chemical  purification, 
78;  tanks,  transport,  80;  uses  and  statistics,  81;  tests  for  lighting  petroleum, 
83 ;  Treatment  of  crude  benzine,  84. 

Treatment  of  Petroleum  Residues  :  (A)  Lubricating  oils,  86;  "cracking," 
manufacture  of  benzine  from  naphtha,  87 ;  requirements  in  and  analysis  of 
lubricating  oils,  90;  statistics,  93.  (B)  Vaseline,  93.  (C)  Paraffin  wax,  94; 
from  petroleum  residues,  94 ;  from  lignite  tar  and  pyropissite,  95 ;  oils  for  gas, 
98;  asphalte,  pitch  and  bitumen,  99;  bituminous  shale,  100.  Ichthyol,  103; 
ozokerite,  104;  statistics  of  paraffin  wax,  105;  cerasin,  105. 

(6)  UNSATURATED  HYDROCARBONS 106 

I.  Ethylene  Series  (alkylenes  or  olefines),  CreH2re,  106 ;  official  nomenclature, 
106 ;    methods  of    preparation,   107 ;    constitution,    108.     Ethylene,  propylene, 
butylenes,  amylenes,  cerotene,  and  melene,  108-109. 

II.  Hydrocarbons  of  the  Series,  CraH2n_2  :  A.  With  two  double  Unkings  (diol- 
efines  or  allenes) :  allene,  erythrene,  isoprene,  piperylene,  dlallyl,  conylene,  109— 
110.     B.  With  a  triple  linking  (acetylene  series) :  metallic  acetylides,  acetylene, 
110-114. 

III.  Hydrocarbons  of  the  Series  CnH2n_4  and  CwH2n_6,  114. 

BB.    HALOGEN  DERIVATIVES  OF  HYDROCARBONS 
Table  of  the  halogen  derivatives  .         .         .         .         .         .         .         .         .115 

I.  Halogen  Derivatives  of  Saturated  Hydrocarbons  :  properties,  114;  pre- 
paration, 115.     Methyl  chloride,  116.     Methyl  iodide,  117.     Ethyl  chloride,  117. 
Isopropyl  iodide  and  butyl  iodides,   117.     Methylene,   ethylene,  and  ethylidene 
halogen  derivatives,   118.     Chloroform,    118-121.     lodoform,    121.     Polychloro- 
derivatives,  122. 

II.  Halogen  Derivatives  of  Unsaturated  Hydrocarbons,  123;  allyl  chloride, 
123.     Tetrabromoethane,  123. 

CC.   ALCOHOLS 

I.  SATURATED  MONOHYDRIC  ALCOHOLS 124 

Nomenclature,  125.  Methods  of  formation  of  monohydric  alcohols,  125. 
Table  of  monohydric  saturated  alcohols,  126.  Methyl  Alcohol,  127-130.  Ethyl 
Alcohol,  130.  Solid  alcohol,  131.  Bacteriology,  132.  Enzymes,  134.  Oxy- 
dases,  peroxydases,  135.  Biogen  hypothesis,  toxins,  liquid  crystals,  origin  of 
life,  137.  Industrial  preparation  of  alcohol  :  prime  materials,  140.  Alcoholic 
fermentation,  145.  Yeast  industry,  149.  Factors  facilitating  6r  retarding 
fermentation,  151.  Practice  of  fermentation,  152.  Losses  and  yields,  153. 
Table  for  the  calculation  of  the  attenuation  of  fermented  saccharine  worts,  154. 
Amylo  process,  155.  Distillation  of  fermented  liquids,  158.  Rectification  of 
alcohol,  164.  Other  raw  materials  for  alcohol  manufacture,  166.  A'.cohol 
from  fruit,  167.  Alcohol  from  woody  matter,  167.  Alcohol  from  the  sulphite 
liquors  of  paper  works,  169.  Alcohol  from  wine,  lees,  withered  grapes,  169. 
Alcohol  from  green  maize,  171.  Synthetic  alcohol,  171.  Refining  and  purifi- 


CONTENTS  xi 

PAGE 

cation  of  spirit,  172.  Tests  for  the  purity  of  alcohol,  172.  Fusel  oil,  172. 
Alcohol  meters,  173.  Quantitative  estimation  of  alcohol,  174.  Windisch's 
table,  175.  Uses  and  denaturation  of  alcohol,  176.  Statistics  and  fiscal 
regulations,  179.  Utilisation  of  distillery  residues,  182. 

Alcoholic  Beverages  :  Wine,  184.  Alcoholism,  184.  Marsala,  190.  Ver- 
mouth, 190.  Cider,  190.  Liqueurs,  190.  Fermented  milk  (kephir,  koumis, 
galazin),  191. 

Beer,  191 :  barley,  hops,  water,  germination,  kilning  of  malt,  mashing, 
Balling's  table,  192-201 ;  infusion  and  decoction  mashing,  201 ;  boiling  of  the 
wort  with  hops,  203 ;  fermentation,  204 ;  attenuation,  207.  The  Nathan-Bolze 
rapid  process,  £08 ;  lacking,  pitching  of  casks,  209 ;  pasteurisation,  210 ;  alcohol- 
free  beer,  211 ;  composition  of  beer,  211 ;  analysis  of  beer,  212;  statistics,  212. 
Sodium  ethoxide  and  calcium  ethoxide,  214. 

Higher  Alcohols,  214;   propyl,  butyl,  amyl,  etc.,  214-216. 

II.  UNSATURATED  MONOHYDRIC  ALCOHOLS  :  vinyl,  allyl,  propargyl,  etc., 
216. 

III.  POLYHYDRIC  ALCOHOLS.     (A)  Dihydric  alcohols  or  glycols,  216.     (B)  Tri- 
hydric  alcohols  :    glycerol,  217.     (C)  Tetra-  and  poly-hydric  alcohols  :    acetyl 
number,  224.     Erythritol,  arabitol,  mannitol,  dulcitol,  sorbitol,  225-226. 

DD.   DERIVATIVES   OF  ALCOHOLS 

(A)  DERIVATIVES  OF  MONOHYDRIC  ALCOHOLS        .         .         .         .         .226 

I.  Ethers,    226 ;     methyl   ether,   228 ;     ethyl   ether :     properties,   industrial 
preparation,  229-232. 

II.  Thio-alcohols  and  Thio-ethers,  233.    Sulphonal,  233. 

III.  Alkyl  Derivatives  of  Inorganic  Acids,  234:  (1)  of  sulphuric  acid,  235; 
(2)  of  sulphurous  acid,  235;    (3)  of  nitric  acid,  235;    (4)  of  nitrous  acid,  235; 
(5)  nitro-derivatives  of  hydrocarbons,  235;    (6)  various  acids,  237;  (7)  Deriva- 
tives of  hydrocyanic  acid  :   (A)  Nitriles ;    (B)  Isonitriles,  237-239. 

IV.  Nitrogenated  Basic  Alkyl  Compounds  (amines),  239 ;  methylamine,  240 ; 
dimethylamine,  trimethylamine,  ethylamine,  diethylamine,  triethylamine,  241 ; 
alkylhydrazines,   azoimides,   a-  and  /3-alkylhydroxylamines,  diazo-compounds, 
241-242. 

V.  Phosphines,   Arsines,   and  Alkyl-metallic   Compounds.     Grignard   re- 
action, 242-243.  . 

VI.  ALDEHYDES  AND  KETONES        .         .         .     •    .         .         .         .     243 
(a)  Aldehydes  :     Functions,    constitution,    chemical    properties,     244. 

Acetal  derivatives,  245.  Aldoximes,  hydrazones,  semicarbazones,  hydr- 
oxamic  acids,  246.  Formaldehyde  :  preparation,  properties  and  analysis, 
247.  Acetaldehyde,  acetal,  250.  Higher  aldehydes,  251.  Chloral  and 
its  hydrate,  251 .  Aldehydes  with  unsaturated  radicals  :  acrolem,  croton- 
aldehyde,  citral,  etc.,  251-252. 

(6)  Ketones  :  Properties,  preparation,  252.  Ketoximes,  isonitroso- 
ketones,  253.  Acetone,  253;  mesityl  oxide,  phorone,  butanone,  255-256. 
Ketenes,  256. 

(B)  DERIVATIVES  OF  POLYHYDRIC  ALCOHOLS 256 

JEthyl  ether  of  glycol,  glycolsulphuric  acid,  Ethylenecyanohydrin,  Ethylene 
oxide,  256;  Taurine,  Glycide  alcohol,  Glycerophosphoric  acid,  etc.,  257.  Nitric 
ethers  of  glycerol,  258. 

Explosives  :  Theory  of  explosives,  259.  Chemical  reactions  of  explosives : 
heat  of  explosion,  259;  mechanical  work  of  explosives,  260;  temperature  of 
ignition,  261 ;  pressure  of  the  gases,  261 ;  charging  density,  262 ;  crushers,  262 ; 
specific  pressure,  262.  Velocity  of  explosion,  263;  shattering  and  progressive 


xii  CONTENTS 

PAGE 

explosives,  263;  velocity  of  combustion,  263;  initial  shock  and  course  of  ex- 
plosion, 264 ;  determination  of  explosion,  264 ;  explosive  wave,  265 ;  explosion 
by  influence,  265  Classification  of  explosives,  266.  Black  powder,  266; 
manufacture,  267.  Prismatic  powder  for  cannons,  272.  Nitroglycerine  and 
dynamites,  273.  Trinitroglycerine,  275;  manufacture,  277;  uses,  282.  Dyna- 
mites, 282 ;  with  inactive  absorbents,  283 ;  with  active  bases,  285.  Nitros'  arch, 
285.  Nitrocellulose,  285.  Guncotton :  preparation,  manipulation,  compres- 
sion, uses,  288-294.  Collodion-cotton  for  gelatine  dynamite,  dynamite  and 
smokeless  powders,  294.  Smokeless  powders,  295.  Powder  B,  296.  Gelatine  .' 
dynamites,  298.  Military  smokeless  powders,  300.  Smokeless  and  flameless 
explosives,  303.  Shattering  explosives,  303.  Picric  acid,  303.  Trinitrotoluene, 
304.  Sprengel  explosives,  304.  Chlorate  and  perchlorate  powders,  304. 
Safety  explosives,  305.  Detonators  and  caps,  308.  Fulminate  of  mercury,  308. 
Fuses,  310.  Various  powders,  311.  Destruction  of  explosives,  312.  Storage 
and  carriage  of  explosives,  312.  Analysis  and  testing  of  explosives,  313.  Uses, 
318.  Statistics,  319. 

EE.   ACIDS 

I.  SATURATED  MONOBASIC  FATTY  ACIDS,  CnH2nO2 319 

Table,  320.  General  methods  of  preparation,  320.  Affinity  constants,  321. 
Separation,  324 ;  constitution,  324.  Formic  Acid,  324.  Acetic  Acid,  328 : 
Oudeman's  table  of  specific  gravity,  329;  manufacture,  329;  distillation  of 
wood,  330;  utilisation  of  wood-waste,  333;  pyroligneous  acid,  335;  calcium 
acetate,  337.  Uses,  statistics,  and  price  of  acetic  acid,  339.  Manufacture 
of  vinegar,  340.  Analysis  of  vinegar,  344.  Salts  of  Acetic  Acid  :  potassium, 
sodium,  ammonium,  calcium,  ferrous  and  ferric  acetates,  neutral  and  basic 
aluminium  acetates,  silver  acetate,  neutral  and  basic  lead  acetates,  chromic,  stannous, 
and  copper  acetates,  345-348.  Propionic  Acid,  348.  Butyric  Acids  :  (1)  Normal 
butyric  acid,  348;  (2)  isobutyric  acid,  349.  Valeric  Acids  :  (1)  Normal  valeric 
acid,;  (2)  isovaleric  acid;  (3)  ethylmethyla-cetic  acid;  (4)  trimethylacetic  acid, 
349.  Higher  Acids  :  Caproic,  heptoic,  caprylic,  nonoic,  undecoic,  lauric,  myristic, 
349-350.  Palmitic  Acid,  350.  Margaric  acid,  350.  Stearic  acid,  350.  Cerotic 
acid,  351. 

II.  MONOBASIC  UNSATURATED  FATTY  ACIDS          .         .      "  .        ..         .351 

A.  OLEIC  OR  ACRYLIC  SERIES  :  Table,  351.     General  methods  of  forma- 
tion, 351 ;  general  properties,  353.    Acrylic  Acid,  C3H402,  354.    Crotonic  Acids, 
C4H602 :    (a)  vinylacetic  acid,  355 ;    (ba)  solid  crotonic  acid,  355 ;  (6/3)  liquid 
crotonic   acid,   355;    (c)   methylmethyleneacetic    acid,  356.     Pentenoic    Acids, 
C5H802  :  (a)  angelic  acid,  356 ;  (6)  tiglic  acid,  357.     Pyroterebic  Acid,  C6H1002, 

357.  y-AHylbutyric   Acid,   C7H12O2,    357.    Teracrylic  Acid,    C8H14O2,    357. 
Citronellic  Acid,  C10H18O2;  rhodinic  acid,  358.     Undecenoic  Acid,  CUH2002, 

358.  Hypogaeic  Acid,  C16H30O2,  358.     Oleic  Acid,  C18H34O2,  358.     Elaidic 
Acid,  359 ;  Iso-oleic  Acid,  359 ;  A^-oleic  acid,  359.     Erucic  Acid,  C22H4202, 
360;  Brassidic  Acid,  360;  Isoerucic  Acid,  360. 

B.  UNSATURATED  ACIDS  OF  THE  SERIES  CraH2ra_402    .         .         .360 

(a)  Acids  with  a  Triple  Linking  (propiolic  series) :  Table,  360.  Preparation, 
360;  properties,  261.  Propiolic  Acid,  C3H202.  Tetrolic  Acid,  C4H402.  De- 
hydroundecenoic  Acid,  CnH18O2.  Undecolic  Acid,  361.  Stearolic  Acid, 
C18H32O2.  Tariric  Acid.  Behenolic  Acid,  C22H40O2,  362. 

(6)  Acids  with  two  Double  Linkings  (diolefine  series),  362.  /3-Vinylacry- 
lic  Acid,  C5H602.  Sorbinic  Acid,  C6H802.  Diallylacetic  Acid,  C8H12O2. 
Geranic  Acid,  C18H32O2.  Linolic  Acid;  Drying  oils,  363.  a-Elseostearic 
Acid,  364. 

C.  ACIDS  WITH  THREE  DOUBLE  LINKINGS,  C^H^^O^  Citrylidene- 
acetic  Acid,  C12H18O2.  Linolenic  and  Isolinolenic  Acids,  C18H3002.  Jecorinic 
Acid,  C18H3002,  364. 


CONTENTS  xiii 

PAGE 

III.  POLYBASIC  FATTY  ACIDS    .........     364 


A.  SATURATED  DIBASIC  ACIDS,  ^H^CO.^,  364;  Table,  365;  pre- 
paration, properties,  365.     Oxalic  acid,  C2H2O4,  366.     Salti  of  oxalic  acid,  368. 
Malonic  Acid,  C3H4O4,  368.    Ethyl  malonate,  its  use  in  syntheses,  368.    Table 
of  malonic  add  derivatives,  369.     Succinic  Acid,  C4H604,  370.     Amber,  370. 
Homologous    derivative?,  871.     Isosuccinic    Acid,  371.     Pyrotartaric   acids, 
C4H904  :  glutaric  acid,  pyrotartaric  add,  372.     Higher  Homologues,  372.    ft- 
Methyladipic,  Suberic,  Azelaic  and  Sebacic  acils,  372. 

B.  UNSATURATED  DIBASIC  ACIDS,  CttH2ra_4O2          .         .         .         .373 

OLEFINEDICARBOXYLIC  ACIDS  :  Table,  S73,  Fumaric  Acid,  374.  Maleic 
Acid,  C4H4O4.  Itaconic  Acid,  C5H604.  Mesaconic  Acid,  C5H604,  374.  Citra- 
conic  Acid,  C5H604.  Glutaconic  Acid,  C5H6O4.  Pyrocinchonic  Acid  and 
Anhydride,  C6H804.  Korner  and  Menozzi  reaction  of  amino-acids,  375.  Hydro- 
muconic  Acids,  C6HdO4.  Diolefinedicarboxylic  Acids.  Acetylenedicarboxylic 
Acids,  376. 

C.  TRIBASIC  ACIDS,  etc  ......         .         .         .         .376 

Tricarballylic  Acid,  C3H6(COOH)3.    Camphoronic  Acid,  C9H1406.    Aconitic 
Acid,  CgHgOe,  376. 


D.  TETRABASIC  ACIDS 376 

FF.    DERIVATIVES  OF  ACIDS 
.1.  HALOGEN  DERIVATIVES •    .     377 

(a)  Halogenated  Acids,  377.  Table,  378.  Cyano-acids,  377.  Monochlor- 
acetic  Acid,  379. 

(6)  Acid  Halides  :  chloran hydrides ;  aoetyl  chloride;  acetyl  icdide,  etc., 
379-380. 

II.  ANHYDRIDES 380 

Properties,  preparation,  Table,  380-381.     Acetic  Anhydride,  381. 

III.  HYDROXY-ACIDS 383 

A.  SATURATED  DIVALENT  MONOBASIC  ACIDS        ....     383 

Preparation,  properties,  constitution,  383;   lactides,  lactones,  384. 

Glycollic  Acid,  OH  '  CHg  *  COOH,  and  its  derivatives  (anhydride,  glycollide. 
etc.),  384.  Glycocoll,  385. 

Lactic  Acids,  02H4(OH)(COOH) :  (1)  i-Ethylidenelactic  acid  (of  fermentation), 
386;  Alanine,  389.  (2)  d-Ethylidenelactic  (or  sarcolactio)  acid.  (3)  1-EthyI- 
idenelactic  acid.  (4)  Ethylenelactic  acid,  389. 

Hydroxybutyric  Acids,  C3H6(OH)(COOH) :  a-Hydroxybutyric  acid.  a-Hydr- 
ox  isobutyric  acid.  /3-Hydroxybutyric  acid,  389. 

Higher  Hydroxy-Acids.  Hydroxyvaleric,  hydroxycaproic,  hydroxymyristic, 
hydroxypalmitic,  hydroxystearic,  389. 

B.  UNSATURATED  MONOBASIC  HYDROXY-ACIDS  .         .         .389 

a-,  ft-,  y-,  and  S-Hydroxyolefinecarboxylic  acids:  Ricinoleic  acid;  ricinoleinsul- 
phonic  acid  and  Turkey-red  oil  (sulphoricinate),  390-391. 

C.  POLYVALENT  MONOBASIC  HYDROXY-ACIDS       ....     391 

Glyceric  Acid,  C2H3(OH)2(COOH).  Dihydroxystearic  acid,  C1?H33(OH)2  • 
COOH,  Erythric  Acid,  C3H4(OH)3  •  COOH.  Pentonic  acids.  Arabonic  Acid. 
Hexonic  Acids,  392.  Heptonic  Acids,  393. 


xiv  CONTENTS 

PAGE 

D.  MONOBASIC      ALDEHYDIC      ACIDS      (Aldehydic     Alcohols    and 
Dialdehydes) 393 

Glyoxylic  Acid,  CO2H  •  CHO.  Glycuronic,  Formylacetic,  and  £f-Hydroxy- 
acrylic  Acids,  Gly collie  Aldehyde,  Glyceraldehyde.  Aldol.  Glyoxal,  393.  * 

E.  MONOBASIC    KETONIC    ACIDS     (Keto -alcohols,     Diketones,    and 
Keto-aldehydes)          .  394 

General  properties.  Methods  of  preparation,  a-,  (J-,  and  y-Ketonic  acids. 
Syntheses  with  ethyl  acetate,  394-395.  Pyruvic  Acid,  396.  Acetoacetic  Acid. 
Ethyl  Acetoacetate,  396  Levulinic  Acid,  397. 

KETONIC  ALCOHOLS  :  Acetonealcohol.  Dihydroxyacetone.  Butanol- 
one,  397-398 

DIKETONES  :   Diacetyl.     Dimethylglyoxime.     Acetylacetone,  398-399. 

KETO-ALDEHYDES  :  Pyruvic  Aldehyde  and  Acetoacetaldehyde. 
Hydroxymethyleneacetone.  Levulinaldehyde,  399 

F.  POLYVALENT       DIBASIC      HYDROXY-ACIDS       AND       THEIR 
DERIVATIVES          .  399 

Tartronic  Acid,  399.     Malic  Acid  and  higher  homologues,  399-40,). 

TARTARIC  ACIDS  :  (1)  d-Tartaric  Acid,  400.  (2)  1-Tartaric  Acid. 
(3)  Racemic  Acid.  (4)  Mesotartaric  Acid,  401. 

TARTAR  INDUSTRY  :  Manufacture  of  Tartar,  402.  Analysis  of  tartar, 
403.  Statistics,  403.  Manufacture  of  tartaric  acid,  407 ;  uses  and  statistics, 
409.  A  tificial  tartaric  acid,  410.  Trihydroxyglutaric,  Saccharic  and  Mucic 
Acids,  410. 

DIBASIC  KETONIC  ACIDS,  410.  Mesoxalic  Acid.  Oxalacetic  Acid. 
Acetonedicarboxylic  Acid.  Dihydroxytartaric  Acid,  410-411. 

G.  POLYVALENT  TRIE  ASIC  HYDROXY-ACIDS 411 

Ethane-  and  Piopane-tricarboxylic  Acids,  411.  Tricarballylic  Acid.  Aconitic 
acid,  411.  Citric  Acid.  412.  Tests  for  citric  acid,  413.  Citrus  industry,  413. 
Statistics,  417.  Salts  of  citric  acid,  418.  Higher  p olybasic  hydroxy-acids,  419. 

IV.  THIO-ACIDS  AND  THIO-ANHYDRIDES 419 

Thioacetic  Acid.    Ethanthiolic  Acid.    Acetyl  Sulphide.    Ethyl  Thioacetate. 

V.  AMIDO-ACIDS,    AMINO-ACIDS,    IMIDES,    AMIDINES,     THIOAMIDES, 

IMINO-ETHERS  AND  ANALOGOUS  COMPOUNDS  .         .         .         .419 

A.  Amido-Acids  and  their  Derivatives  :   Primary,  secondary,  and  tertiary 
amides;   alkylated  amides.     Preparation  and  properties  of  amides,  419-421. 

Formamide  ;  Acetamide,  diacetamido ;  OxamicAcid;  Oxamide;  Succin- 
amic  Acid  ;  Succinamide  ;  Glycollamide,  diglyoollirnide ;  Malamic  Acid, 
Malamide,  421. 

B.  IMIDES  AND  IMINO-ETHERS  :  diacatam'de,  iminohydrin  of  glycollic 
acid;    Oximide,  Succinimide,    pyrrole,  pyrrolidine,  succinanil;  Glutarimide, 
421-422. 

C.  AMINO-ACIDS  AND  THEIR  DERIVATIVES  :    Glycocoll,  sarcosine, 
betaine,  aceturic  acid ;  Serine  ;  Leucine  ;  Aspartic  Acid,  glutamic  acid ;  Ethyl 
Diazoacetate;  Lysine,  ornithine,  putrescine,  taurine,  cysteine,  cystine;  Aspara- 
gine,  Aspartamide,  homoaspartic  acid  and  homoasparagine,  422-425. 

D.  AMIDO-  AND   IMIDO-CHLORIDES  :   acetamido-chloride,   acetimino- 
chlorid?,  425. 

E.  THIOAMIDES  :    thioacetamide,  425. 

F.  IMINOTHIOETHERS  :  acetiminothiomethyl  hydriodide,  425. 


CONTENTS  xv 

PAGE 

G.  AMIDINES  :   acetamidine,  426. 

H.  HYDRAZIDES  AND  AZIDES  :  diacethydrazide,  426. 

I.  HYDROXYLAMINE  DERIVATIVES  OF  ACIDS  :  hydroxamic  acids, 
amidoximes,  isuret,  427. 

VI.  CYANOGEN  COMPOUNDS .427 

Cyancgen  :  paracyanogen ;  rubeanhydric  acid  and  flaveanhydric  acid. 
Cyanogen  Chloride.  Cyanic  Acid :  potassium  and  ammonium  cyanates.  Ethyl 
Isocyanate.  Cyanuric  Acid  :  Ethyl  cyanurate  and  isocyanurate.  Fulminic 
Acid,  Fulminuric  Acid,  427-429. 

THIOCYANIC  ACID  AND  ITS  DERIVATIVES.  Potassium,  Ammonium, 
Mercuric,  Silver,  and  Ferric  Thiocyanates.  Ethyl  Thiocyanate.  Allyl 
Thiocyanate,  429^30. 

MUSTARD  OILS  :   methyl,  ethyl,  propyl,  Allyl,  430. 

CYANAMIDE  AND  ITS  DERIVATIVES.  Calcium  cyanamide.  Diethyl- 
cyanamide.  Dicyanodiamide.  Melams  :  Melamine,  Ammeline,  Ammelide, 
430-431. 

VII.  DERIVATIVES    OF   CARBONIC   ACID  .         .         .         .         .         .431 

Esters  of  carbonic  acid.  Ethyl  carbonate,  ethylcarbonic  acid.  Chlorides  of 
Carbonic  Acid.  Chlorocarbonic  acid,  ethyl  chlorocarbonate  and  chloroformate. 
Amides  of  Carbonic  Acid.  Carbaminic  acid,  urethane,  urea,  semicarbazide, 
acetylurea,  allophanic  acid,  ureides,  biuret,  hydantoic  acid,  hydantoin,  431-433. 

DERIVATIVES  OF  THIOCARBONIC  ACID  :  thiophosgene,  trithiocarbonic 
acid,  potassium  xanthate,  xanthonic  acid,  dithiocarbamic  acid,  diethylthiourea. 
Thiourea,  433-434. 

GUANIDINE  AND  ITS  DERIVATIVES  :  nitroguanidine,  aminoguanidine, 
diazoguanidine,  hydrazo-  and  azo-dicarbonamide,  glycocyamine,  sarcosine, 
creatine,  creatinine,  434-435. 

URIC  ACID  AND  ITS  DERIVATIVES  :  ureides,  uro-acids,  diureides;  para- 
banic  acid,  barbituric  acid,  dialuric  acid,  alloxan,  oxaluric  acid,  alloxanic  acid, 
cholestrophane,  methyluracil,  alloxanthine,  murexide,  allantoin,  purine,  di- 
methylpseudouric  acid,  theophylline,  caffeine,  hypoxanthine,  xanthine,  adenine, 
guanine,  uric  acid,  435-437.  Theobromine,  cocoa  and  chocolate,  caffeine  or 
theine,  coffee  and  its  substitutes,  guanine,  xanthine,  adenine,  437-441. 


PART  I.     GENERAL 

IN  Vol.  I.  of  this  treatise l  is  given  a  brief  summary  of  the  history  of  chemistry 
and  of  those  portions  of  physico-chemical  theory  which  are  necessary  for  the 
interpretation  of  chemical  phenomena. 

Hence,  this  course  of  organic  chemistry  assumes  in  the  reader  a  knowledge 
of  the  fundamental  chemical  laws  and  ideas,  methods  of  determining  molecular 
weights,  and  so  on. 

The  separate  treatment  of  the  carbon  compounds,  which  is  termed  organic 
chemistry,  is  a  purely  didactic  convenience  and  somewhat  of  a  habit,  there 
being  no  sound  foundation  to  justify  a  distinction  between  organic  and  inorganic 
chemistry. 

This  division  of  the  subject  dates  back  to  the  time  of  Lemery,  who,  in 
1 675,  regarded  the  substances  of  the  animal  and  vegetable  kingdoms  as  distinct 
from  those  of  the  mineral  kingdom,  and  to  1820,  when  Berzelius  justified  the 
separation  by  stating  that  the  preparation  of  organic  compounds  required  the 
intervention  of  vital  force,  whilst  inorganic  compounds  could  be  prepared 
artificially  in  the  laboratory.  This  view  was,  however,  abandoned  when,  in« 
1828,  Wohler  succeeded  in  preparing  urea  (found  in  urine)  from  inorganic 
material  in  the  laboratory,  and  when,  later,  acetic  acid  was  prepared  arti- 
ficially. Subsequently,  the  number  of  so-called  organic  compounds  obtained 
synthetically  has  increased  almost  without  limit. 

There  exists  to-day  no  reason  for  a  distinction  between  organic  and  inorganic 
compounds;  the  first  comprise  a  group  of  carbon  compounds  embracing  an 
immense  number  (over  150,000)  of  substances,  which  exhibit  certain  common 
characters  and  are  conveniently  studied  by  themselves. 

It  had  already  been  recognised  by  Lavoisier  that  all  so-called  organic 
compounds,  originating  in  organised  bodies,  contain  carbon,  hydrogen,  and 
oxygen,  and  that  many  of  them,  especially  those  of  the  animal  kingdom, 
contain  also  nitrogen  and  sometimes  sulphur,  phosphorus,  halogens,  and  metals. 

The  study  of  organic  compounds  is  as  old  as  the  human  race,  which,  from 
the  most  remote  times,  has  prepared  alcohol  and  acetic  acid  from  vegetable 
juices  (the  must  of  the  grape  and  other  fruit,  etc.). 

After  the  discoveries  of  Lavoisier  and  the  investigations  of  Berzelius, 
organic  chemistry  began  to  acquire  special  importance,  and  Liebig,  by  intro- 
ducing simple  and  exact  methods  for  the  analysis  of  organic  compounds, 
rendered  most  valuable  help  to  the  wonderful  theoretical  and  practical  develop- 
ment which  has  been  shown  by  this  branch  of  chemistry  during  the  past  fifty 
years,  and  which  has  been  largely  responsible  for  the  impulse  given  to  progress 
and  civilisation  in  the  nineteenth  century. 

In  order  to  study  the  innumerable  derivatives  of  carbon,  to  be  able  to  obtain 
separate  individuals  and  to  characterise  them  by  means  of  their  chemical  and 
physical  properties,  then  to  group  and  classify  them  and  to  deduce  in  a  more 
or  less  general  way  the  laws  they  obey,  it  was  necessary  to  isolate  and  prepare 
in  the  pure  state  these  separate  chemical  individuals. 

1  E.  Molinari,  "  Inorganic  Chemistry  ";  translated  by  T.  H.  Pope,  1920. 
VOL.  II.  1 


2  OR  G  A  N  I  C    C  H  E  M  I  S  T  R  Y 

PUP  j  HC  AT  I  ON    C-F   ORGANIC   SUBSTANCES 

The  purification  of  organic  substances  is  not  so  easy  to  effect  as  might  at  first  appear. 
Pure  substances  are  characterised  by  certain  physical  constants  (boiling-point,  melting- 
point,  crystalline  form,  etc.),  which  serve  to  show  if  a  substance  is  in  a  suitable  condition 
for  chemical  analysis. 

The  chemical  processes  of  purification  may  be  deduced  from  the  chemical  properties 
of  the  substances  themselves,  as  described  in  Parts  II  and  III  of  this  treatise;  general 
physical  methods  effect  purification  by  means  of  suitable  solvents  (water,  alcohol,  ether, 
light  petroleum,  acetic  acid,  benzene,  acetone,  chloroform,  carbon  disulphide,  etc.),  which 
separate  certain  substances  from  others  more  or  less  soluble ;  or,  in  many  cases,  purifica- 
tion is  brought  about  by  crystallisation,  a  solution  of  the  impure  substance  in  a  suitable 
hot  solvent  depositing — on  gradual  cooling  or  partial  evaporation  of  the  solvent — the 
pure  substance  in  characteristic  and  well-defined  crystalline  forms,  which  may  be  controlled 
by  measuring  the  angles  and  determining  the  axial  ratios  of  the  crystals. 

Impurities  separate  sometimes  before  and  sometimes  after  the  crystallisation  of  the 
substance  under  examination,  so  that  recourse  is  had  to  fractional  crystallisation,  which, 
when  repeated,  may  give  excellent  results. 

In  certain  cases,  substances  are  purified  by  sublimation.1  When  pure,  a  liquid  has  a 
constant  boiling-point  for  a  definite  pressure  (Vol.  I.,  p.  85),  and  this  is  determined  by  dis- 
tilling the  liquid  in  a  flask  with  a  lateral  tube,  a  thermometer  being 
arranged  in  the  neck  of  the  flask  without  its  bulb  dipping  into  the 
boiling  liquid.  The  temperature  of  the  vapour  gives  the  boiling-point 
of  the  liquid ;  the  vapour  escapes  from  the  side-tube  and  is  condensed 
by  means  of  a  Liebig's  condenser,  formed  of  an  inclined  glass  tube 
surrounded  by  a  wider  tube  through  which  water  circulates  from  the 
lower  to  the  upper  end  (Fig.  2). 

The  boiling-point  of  a  very  small  quantity  of  substance  may  be 
accurately  determined  by  means  of  the  arrangement  shown  in  Fig.  3  : 
a  few  drops  of  the  liquid  are  introduced  into  a  small  tube,  d,  closed  at 
the  bottom  and  drawn  out  into  a  narrowed  part.  Into  the  liquid  dips 
a  capillary  tube,  sealed  at  the  point  a  by  fusing  the  glass.  The  tube  is 
FIG.  1.  attached  to  the  thermometer,  c,  and  the  whole  immersed,  to  the  depth 

of  a  few  centimetres,  in  a  liquid  having  a  boiling-point  higher  than 
that  of  the  liquid  under  examination.  Heat  is  now  gradually  applied,  superheating  being 
prevented  by  the  air-bubbles  issuing  from  the  lower  end  of  the  capillary  tube.  When 
the  boiling-point  is  reached,  bubbles  form  very  rapidly  at  the  bottom  of  the  liquid,  and 
the  boiling-point  is  read  off  on  the  thermometer. 

Certain  substances  which  readily  decompose  on  boiling  at  the  ordinary  pressure  can 
be  distilled  unchanged  at  a  constant,  but  somewhat  lower,  temperature  by  lowering  the 
pressure,  i.  e.,  by  distilling  in  a  vacuum  (see  later).  For  this  purpose  use  is  made  of  a 
mercury  or  water  pump  (Sprengel). 

When  two  liquids  are  mixed,  they  may  be  separated  almost  completely  by  fractional 
distillation,  if  there  is  a  wide  interval  of  temperature  between  their  boiling-points.  In 
consequence  of  the  partial  pressure  of  the  components,  at  different  temperatures  mix- 
tures distil  over  which  contain  varying  proportions  of  these  components ;  the  liquid  with 
the  lower  boiling-point  first  preponderates  in  the  distillate,  while  at  higher  temperatures 
that  with  the  higher  boiling-point  predominates.  On  repeated  redistillation  of  the  two 
extreme  fractions  separately,  the  two  liquids  may  be  obtained  in  the  pure  state.  In  certain 
cases,  however,  a  mixture  of  two  liquids  does  not  exhibit  a  regular  progression  in  the 
vapour  pressure  corresponding  with  the  preponderance  of  one  or  other  of  the  two 
components.  There  are,  indeed,  liquids  which,  when  mixed  in  certain  proportions,  show 
a  minimum  vapour  pressure — lower  even  than  that  of  the  less  volatile^  component — whilst, 

1  Sublimation  takes  place  with  many  solid  substances  and  consists  in  the  passage  from  solid 
to  vapour  on  gentle  heating,  and  from  the  state  of  vapour  to  the  solid  crystalline  condition  when 
the  vapours  come  into  contact  with  a  cold  body,  these  changes  taking  place  directly  and  not 
by  way  of  the  liquid  state.  Usually  the  substance  is  placed  on  a  clock-glass,  covered  by  a  per- 
forated filter-paper  and  by  a  funnel;  when  the  clock-glass  is  heated  on  a  sand-bath,  the  pure 
sublimed  crystals  collect  on  the  walls  of  the  funnel  (Fig.  1).  In  some  cases,  the  sublimation  is 
carried  out  in  a  vacuum. 


RECTIFICATION 


3 


on  the  other  hand,  a  mixture  of  two  liquids  sometimes  has  a  vapour  pressure  greater  than 
that  of  its  more  volatile  constituent ;  the  two  liquids  cannot  then  be  separated  by  fractional 
distillation,  especially  when  their  boiling-points  are  not  far  apart.1  In  these  cases  good 


FIG.  2. 


FIG.  3. 


results  are  obtained  practically  by  employing  so-called  rectification,  this  consisting  in 
distilling  the  liquid  mixture  through  a  Le  Bel  and  Henninger  (1874)  rectifying  tube 
(Fig.  4),  which  is  fitted  at  regular  intervals  with  discs  of 
platinum  gauze,  and  above  these  takes  the  form  of  a  series  of 
two  or  more  bulbs,  a  lateral  tube  being  so  placed  as  to  lead 
the  liquid  condensing  in  any  bulb  baek  to  the  bulb  below  it. 
When  the  liquid  boils,  the  mixed  vapours  pass  up  the  tube 
and  meet  the  first  gauze  disc,  where  the  vapour  of  the  less 
volatile  liquid  is  condensed  in  greater  proportion  than  the 
other,  so  that  the  vapour  reaching  the  second  gauze  is  richer 
in  that  of  the  more  volatile  liquid;  a  similar  process  occurs 
at  the  successive  gauzes  and  in  the  bulbs  above  them,  so 
that  the  vapour  passing  through  the  uppermost  bulb  is  that 
of  the  more  volatile  liquid,  and  this  passes  down  the  side- 
tube  (at  the  mouth  of  which  the  thermometer  is  placed)  to 
the  condenser.  During  this  rectification  the  cooling  produced 
by  the  outer  air  and  the  consequent  condensation  of  the 
vapours  result,  in  the  rectifying  tube,  in  a  stream  of  liquid 
flowing  down  the  walls  of  the  tube;  this  liquid  film  meets 
the  ascending  vapours  and  gives  up  to  them  its  more  volatile 
constituent  and  takes  up  from  them  their  less  volatile  com- 
ponent, so  that  only  the  vapour  of  the  more  volatile  liquid 
reaches  the  top  of  the  tube,  while  the  less  volatile  liquid  is 
returned. 

Similar  results  are  obtained  by  HempeVs  rectifying  column  (1881),  which  is  filled  with 
glass  beads  (Fig.  5).  With  this  also  the  phenomenon  of  rectification  which  goes  on  often 

1  Theory  of  Fractional  Distillation.  We  shall  see  later  the  relations  existing  between  the 
boiling-point  and  the  composition  and  chemical  constitution  of  organic  substances  (homologous 
series,  isomerides,  etc.).  Of  interest  at  the  present  juncture  is  the  behaviour  on  distillation  of 
a  mixture  of  two  liquids  which  dissolve  one  in  the  other  in  all  proportions. 

According  to  Wanklyn  and  Berthelot,  when  a  mixture  of  equal  weights  of  two  liquids  is 
distilled,  the  proportions  of  the  two  in  the  distillate  depend  not  only  on  their  proportions  in 


FIG.  4. 


FIG.  5. 


4 

permits  of  the  separation  of  liquids  with  boiling-points  quite  close  together.  This 
phenomenon  has  important  applications  in  the  alcohol  industry  (see  later),  in  the  manu- 
facture of  oxygen  and  nitrogen  from  liquid  air,  in  the  preparation  of  liquid  sulphur  dioxide 
(Vol.  T.,  pp.  280  and  340),  and  in  many  other  industries. 


FIG.  6. 

-  In  many  cases  substances  (liquid  or  solid)  are  purified  by  distillation  in  a  current  of 
steam,  certain  of  them  being  volatile  under  these  conditions  even  when  their  boiling- 
points  are  above  that  of  water;  in  the  distillate  the  substance  often  separates  owing  to 
its  insolubility  in  water.  An  arrangement  used  in  the  laboratory  is  shown  in  Fig.  6,  steam 
being  generated  in  A  and  passing  through  the  substance  to  be 
distilled  in  the  flask,  B,  which  may  be  heated  directly  with  a 
flame. 

In  some  instances  the  distillation  is  effected  by  means  of 
superheated  steam  (150°  to  350°),  which  is  obtained  by  passing 
steam  through  a  coil  of  iron  or  copper  tubing  heated  with  a 
bunsen  burner  (Fig.  7). 


FIG.  7. 

A  number  of  substances  decompose  when  heated  at  the  ordinary  pressure,  whilst  they 
distil  unchanged  in  a  more  or  less  perfect  vacuum,  owing  to  a  marked  lowering  of  the 

the  original  liquid  and  on  their  vapour  pressures  at  the  boiling-point  of  the  mixture  itself,  but 
also  on  the  reciprocal  adhesion  of  the  constituent  liquids  and  on  their  vapour  densities.  When  a 
mixture  of  two  miscible  liquids,  in  equal  weights,  is  distilled,  the  quantity  of  each  component 
which  distils  may  (disregarding  certain  exceptions)  be  calculated  by  multiplying  the  vapour 
pressure  (at  the  boiling-point  of  the  mixture)  by  the  vapour  density.  Hence  it  can  be  under- 
stood how,  in  some  cases,  the  less  volatile  substance  distils  in  greater  quantity.  Even  if  the 
vapours  that  distil  over  contain  equal  volumes  of  the  two  vapours  (that  is,  equal  numbers  of 
molecules),  the  condensed  liquid  will  contain  a  greater  proportion  by  weight  of  the  constituent 
with  the  higher  molecular  weight.  This  explains  why  water,  with  a  low  vapour  density,  causes 


MELTING-POINT  5 

boiling-point.  Of  the  many  different  forms  of  apparatus  employed  in  the  laboratory  for 
this  purpose,  that  of  Bredt  is  illustrated  in.  Fig.  8.  An  ordinary  thick-walled  distilling 
flask,  A,  is  used,  its  side-tube  being  connected  with  the  condenser  a  and  with  the  collecting 
apparatus,  which  consists  of  a  flask,  d,  and  three  tubes,  e,  of  thick  glass,  and  is  joined  to 
the  condenser  by  means  of  a  perforated  stopper ;  the  pump  by  which  the  air  is  withdrawn 
from  the  whole  apparatus  is  connected  with  the  tube  c,  which  communicates  also  with 
a  manometer  to  show  the  extent  of  the  vacuum  attained.  Superheating  and  consequent 
bumping  of  the  liquid  are  avoided  by  the  insertion  of  the  tube  b,  the  lower  end  of  which 
is  drawn  out  to  a  capillary  and  dips  below  the  surface  of  the  liquid,  while  the  upper  end 
is  closed  with  a  piece  of  rubber  tubing  fitted  with  a  screw-clip;  by  means  of  this  tube,  into 
which  also  the  thermometer  may  be  introduced,  a  slow  current  of  air  or  other  inert  gas, 
controlled  by  means  of  the  screw-clip,  is  allowed  to  bubble  through  the  liquid  during  the 
distillation.  The  flask  is  heated  in  a  bath  of  oil  or  fusible  alloy,  and,  if  the  distillate  is 
very  dense,  no  water  need  be  passed  through  the  condenser.  The  first  portion  distilling 
over  at  a  definite  temperature  is  collected  in  d,  and  when  the  temperature  rises  suddenly, 
the  collecting  apparatus  is  rotated  so  that  the  distillate  is  collected  in  one  of  the  tubes,  e ; 
when  the  thermometer  no  longer  indicates  a  constant  temperature  another  of  the  tubes,  e, 
is  employed,  and  so  on. 

MELTING-POINT.  Whilst  with  liquids  the  boiling-point  is  generally  used  as  a 
criterion  of  purity,  for  solids  the  melting-point  is  mostly  employed  for  this  purpose,  and 
in  certain  cases  also  the  boiling-point.  So  long  as  the  substance  is  impure,  the  melting- 
point  is  usually  too  low.  The  melting-point  is  determined  by  introducing  a  few  centigrams 
of  the  substance  into  a  very  narrow,  almost  capillary  glass  tube,  closed  at  the  bottom 

substances  with  higher  boiling-points  (ethereal  oils,  naphthalene,  etc.)  to  distil,  since,  although 
the  latter  have  low  vapour  pressures,  their  molecular  weights  are  high. 

Of  frequent  occurrence  are  mixtures  of  two  miscible  (one  in  maximum  or  minimum  ratio 
to  the  other)  liquids,  which,  on  distillation,  do  not  separate,  but  distil  together  in  unaltered 
proportions  at  constant  temperature.  Thus,  16  parts  of  alcohol  and  84  of  CC14  boil  at  64-9°, 
and  32  parts  of  alcohol  and  68  of  benzene  at  67-8°;  if  59-8  parts  of  CC14  (b.-pt.  76-4°)  are  added 
to  a  mixture  of  12  parts  of  alcohol  with  32-2  of  benzene,  which  begins  to  boil  at  67-8°,  the  boiling- 
point  of  the  ternary  mixture  falls  to  65-8°.  Further,  alcohol,  water,  and  benzene  in  certain 
proportions  yield  a  ternary  mixture  which  boils  at  a  lower  temperature  than  any  of  its  separate 
components  and  cannot  be  separated  into  the  latter;  if,  however,  excess  of  benzene  is  added, 
repeated  distillation  yields  the  benzene  and  water  together  with  part  of  the  alcohol,  so  that  pure 
alcohol  finally  remains  (Young,  1894  and  1902;  Kablukov,  Solomonov,  and  Galine,  1903; 
Golodetz,  1912).  A  mixture  of  31  per  cent,  of  acetic  acid  (b.-pt.  118°)  with  69  per  cent,  of  toluene 
(b.-pt.  110-4°)  boils  completely  without  separation  at  104°.  With  2  per  cent,  of  acetic  acid, 
benzene  (b.-pt.  80-4°)  forms  an  inseparable  mixture  boiling  at  80°,  which  is  the  minimal  boiling- 
point  for  benzene -acetic  acid  mixtures.  If  to  100  grams  of  the  above  toluene-acetic  acid  mixture 
are  added  1800.  grams  of  benzene  (rather  more  than  is  required  to  give  a  benzene -acetic  acid 
mixture  with  2  per  cent,  of  the  acid),  the  liquid  commences  to  boil  at  79-6°,  and  up  to  81-8° 
1900  grams  distil,  containing  always  about  1-85  %  of  acetic  acid,  the  residue  consisting  of  31  grams 
of  pure  toluene.  Toluene  containing  19-6  per  cent,  of  water  boils  unchanged  at  84-1°,  and  if 
67  grams  of  water  are  added  to  400  grams  of  the  above  toluene -acetic  acid  mixture,  distillation 
yields  in  succession,  (1)  between  84°  and  85°,  355  grams  containing  all  the  toluene  and  about 
4  per  cent,  of  acetic  acid,  which  is  separable  by  a  further  distillation,  (2)  about  28  grams  of 
65  per  cent,  acetic  acid,  and  (3)  about  82  grams  of  95  to  98  per  cent,  acetic  acid,  about  one-half 
of  this  being  of  100  per  cent,  strength.  A  mixture  of  60-5  grams  of  benzene,  242  grams  of  toluene, 
and  39-5  grams  of  methyl  alcohol  (the  last  gives  with  60-5  per  cent,  of  benzene  a  mixture  boiling 
unchanged  at  58-35°)  yields  at  58-2°  to  59-8°,  94  grams  containing  methyl  alcohol  and  benzene 
in  the  above  ratio,  and  at  110°,  228  grams  of  pure  toluene.  From  a  mixture  of  benzene  and 
methyl  alcohol,  pure  benzene  may  be  separated  by  distillation  in  presence  of  carbon  disulphide. 

On  distilling  a  mixture  of  two  liquids  not  soluble  one  in  the  other,  the  corresponding  vapours 
do  not  influence  one  another,  and  the  total  pressure  of  the  vapours  is  given  by  the  sum  of  the 
pressures  of  the  two  liquids  at  the  temperature  of  distillation.  The  boiling-point  of  the  mixture 
is  the  temperature  at  which  the  sum  of  the  vapour  pressures  of  the  components  equals  the 
atmospheric  pressure ;  it  should  be  mentioned  that  the  boiling-point  of  such  a  mixture  is  neces- 
sarily lower  than  that  of  the  more  volatile  liquid,  since  here  also  Dalian's  law  of  partial  pressures 
(Vol.  I.,  pp.  73,  619)  holds.  Naumann  (1877)  showed  that,  in  the  vapour  distilling  from  such  a 
mixture,  the  ratio  between  the  volumes  of  the  components  corresponds  with  the  ratio  between 
the  vapour  pressures  of  the  two  liquids  at  the  boiling-point  of  the  mixture ;  hence  the  weights 
of  the  two  components  are  obtained  by  multiplying  these  ratios  by  the  corresponding  densities 
(or  molecular  weights).  By  means  of  this  rule,  Naumann  succeeded  in  determining  the  mole- 
cular weights  of  various  substances  simply  by  distilling  mixtures  of  them.  A  mixture  of  water 
and  isoamyl  alcohol  (b.-pt.  135°)  has  a  constant  boiling-point  of  96°,  and  distils  continuously 
in  the  ratio  of  two  volumes  of  water  and  three  volumes  of  the  alcohol. 


6 


ORGANIC    CHEMISTRY 


(Fig.  9),  the  tube  being  attached  to  the  bulb  of  a  thermometer  dipping  into  a  beaker  of 
concentrated  sulphuric  acid,  oil,  or  paraffin  wax,  which  serves  to  transmit  heat  to  the 
substance.  A  small  glass  stirrer  serves  to  prevent  superheating  of  the  liquid,  and,  when 
the  substance  is  pure,  it  melts  entirely  within  a  degree  and  generally  becomes  transparent. 
When  the  temperature  of  the  bath  approaches  the  melting-point,  the  flame  is  lowered  and 
the  bath  heated  gently  so  that  the  temperature  rises  half  a  degree  every  four  or  five  seconds ; 
only  in  exceptional  cases  should  rapid  heating  be  continued.1 

To  determine  the  melting-point  of  a  fat,  a  tube  drawn  out  to  a  capillary  and  sealed 
at  the  lower  end  (Fig.  10a)  is  held  in  an  inclined  position,  and  one  or  two  drops  of  the  fused 
and  filtered  fat  introduced  into  the  enlarged  part  (Fig.  10a,  A).  When  the  fat  is  solidified, 
the  tube  is  kept  in  a  cool  place  for  twenty-four  hours,  after  which  it  is  attached  vertically 
to  the  bulb  of  a  thermometer ;  it  is  then  heated  in  a  suitable  bath,  note  being  taken  of 
the  temperature  at  which  (1)  fusion  begins,  (2)  the  fat  flows  down  and  obstructs  the 
capillary  (Fig.  106),  and  (3)  the  completion  of  fusion  is  indicated  by  the  entire  liquefaction 
and  transparency  of  the  fat. 


FIG.  9. 


FIG.  10. 


FIG.  11. 


The  melting-point  of  a  fat  may  also  be  determined  by  drawing  it  in  the  fused  condition 
into  a  capillary  tube  blown  out  at  the  middle  into  a  bulb,  which  is  half  filled  with  the  fat 
(Fig.  11) ;  the  upper  end  of  the  tube  is  kept*closed  with  the  finger  until  the  fat  becomes 
solid,  the  empty  part  of  the  tube  being  then  bent  round  as  shown  and  attached,  upside 
down,  to  a  thermometer,  the  whole  being  afterwards  gradually  heated  in  a  beaker  of  water. 
When  the  fat  begins  to  melt  it  flows  into  the  lower  part  of  the  bulb  (Fig.  11  A  b,  right-hand 
view),  and  when  it  is  completely  fused  it  becomes  transparent. 

For  fats  and  paraffin  waxes,  or  waxes  in  general,  and  for  soft  fats  (for  example,  lubricants) 
especially,  an  important  determination  is  that  of  the  dropping-point,  which  is  carried  out, 
according  to  Ubbelohde's  method  (1905),  by  filling  with  the  fat  a  glass  capsule,  e  (Fig.  12, 
natural  size),  10  mm.  long  and  7  mm.  wide,  with  an  orifice  3  mm.  in  diameter  in  the  base; 
a  very  small  thermometer  bulb  is  immersed  in  the  fat  and  the  capsule  then  affixed  to  the 
thermometer  with  a  metal  sheath  having  an  aperture  at  c,  and  three  points,  d,  which 

1  Exact  determinations  require  correction  of  the  thermometric  reading  to  allow  for  the 
cubical  expansion  of  the  mercury  and  glass  of  that  part  of  the  thermometer  not  immersed  in 
the  heated  liquid.  The  observed  melting-point,  t,  is  to  be  increased  by  na  (t  —  t^),  where  n  = 
0-000160  (the  mean  cubical  expansion  of  mercury  in  an  ordinary  glass  tube),  a  is  the  number  of 
degrees  between  the  surface  of  the  -heated  liquid  and  the  top  of  the  mercury  column  and  tt  the 
air  temperature  about  half-way  up  the  mercury  column. 

EXAMPLE:  If  the  indicated  melting-point  is  80°  (t),  while  the  thermometer  dips  into  the 
liquid  as  far  as  the  15°  mark,  so  that  a  =  65  (i.  e.,  80  —  15),  and  the  temperature  half-way  up 
the  mercury  column  is  30°  (^),  the  correction  becomes  0-000160  X  65  X  (80  —  30)  =  0-52°, 
and  the  corrected  melting-point  80-52°. 


QUALITATIVE     ANALYSIS  7 

determine  the  position  of  the  capsule ;  the  thermometer  is  then  fixed  in  a  test-tube  4  cm. 
in  diameter,  dipping  into  a  beaker  of  water,  which  is  heated  so  that  the  temperature  rises 
one  degree  per  minute.  At  the  orifice  of  the  capsule  a  drop  begins  to  form  at  a  certain 
time,  and  when  this  falls  the  temperature  is  read,  and  is  usually  corrected  by  subtracting 
0-5°  to  obtain  the  real  instead  of  the  apparent  dropping- point. 

This  method  has  been  adopted  for  the  examination  of  lubricating  oils  supplied  to  the 
Italian  navy  and  railways. 

The  specific  gravity  of  liquids  also  serves  to  determine  their  purity,  and  the  various 
forms  of  apparatus  used  for  measuring  it  are  described  in  Vol.  I.,  p.  75. 


ANALYSIS   OF   ORGANIC   SUBSTANCES 

As  will  be  seen  later,  many  so-called  organic  substances  are  composed 
of  carbon  and  hydrogen  combined  in  various  proportions ;  a  large  number  of 
them  contain  also  oxygen,  while  nitrogen  is  often  present  and  sometimes 
sulphur,  halogens,  metalloids,  and  metals. 

Analysis  of  these  compounds  may  be  merely  qualitative,  when  only  a  know- 
ledge of  the  constituent  elements  is  required,  or  it  may  be  quantitative,  when 
the  percentage  amount  of  each  of  the  elements  present  is 
determined. 


QUALITATIVE  COMPOSITION.  When  organic  substances  are 
heated  on  platinum  foil  they  either  burn  with  a  flame  or  leave  a 
carbonaceous  residue.  The  presence  of  carbon  and  hydrogen  may  be 
demonstrated  by  heating  a  little  of  the  substance,  mixed  with  cupric 
oxide,  in  a  test-tube  fitted  with  a  delivery  tube,  the  gas  evolved  being 
passed  into  a  clear  solution  of  barium  hydroxide :  if  the  latter  becomes 
turbid,  owing  to  the  formation  of  barium  carbonate,  the  presence  of 
carbon  is  proved,  and  if  drops  of  water  condense  in  the  cold  upper 
part  of  the  tube  the  substance  must  contain  hydrogen. 

The  presence  of  nitrogen  may,  in  many  cases,  be  shown  by  the  smell 
of  burning  wool  or  nails  developed  when  a  little  of  the  substance  is 
heated  on  platinum  foil.  A  more  general  and  certain  test  is  that  devised 
by  Lassaigne  (1843)  :  2  to  3  centigrams  of  the  substance  are  fused  with 
a  piece  of  metallic  potassium  or  sodium  (0-2  to  0-3  gram)  in  a  test-tube, 
which  is  broken  by  plunging  it  while  still  hot  into  a  beaker  containing  FIG.  12. 

10  to  12  c.c.  of  water.  The  alkaline  solution  of  potassium  cyanide 
formed  is  filtered,  mixed  with  a  few  drops  of  ferrous  sulphate  and  ferric  chloride 
solutions  and  boiled  for  two  minutes,  by  which  means  potassium  ferrous  cyanide  is 
formed  (when  nitrogen  is  present  in  the  substance) ;  the  liquid  is  acidified  with  hydro- 
chloric acid,  which  dissolves  the  ferrous  and  ferric  oxides,  the  resulting  ferric  chloride 
reacting  with  the  potassium  ferrocyanide  to  form  the  characteristic  Prussian  blue,  or 
at  least  a  green  solution  which  deposits  Prussian  blue  on  standing.  In  absence  of 
nitrogen,  only  a  yellow  colour  is  obtained.  To  certain  nitrogenous  substances  this  test 
is  not  applicable  (e.g.,  to  diazo-compounds,  which  evolve  nitrogen  too  readily),  and 
in  such  cases  either  the  potassium  is  replaced  by  a  mixture  of  potassium  carbonate 
and  powdered  magnesium  (Castellana,  1904),  or  the  substance  is  fused  with  sodium 
peroxide  and  the  mass  tested  for  nitrate  by  means  of  diphenylamine  (Vol.  I.,  p.  234). 
As  early  as  1825  Faraday  detected  nitrogen  by  heating  the  substance  in  a  tube  with  caustic 
soda  and  soda-lime,  the  evolution  of  ammonia  being  shown  by  means  of  litmus  paper; 
spurting  of  small  portions  of  the  soda  on  to  the  litmus  paper  should  be  prevented  by  passing 
the  vapour  emitted  first  through  a  tube  containing  glass  wool  (see  later,  Quantitative 
Determination) . 

The  presence  of  halogens  (Cl,  Br,  I)  is  determined  by  heating  the  substance  with  pure 
lime,  dissolving  in  water  and  nitric  acid  and  precipitating  the  halogen  with  silver  nitrate. 
Also,  in  many  cases,  the  substance  may  be  heated  with  fuming  nitric  acid  and  silver  nitrate 
in  a  sealed  tube  (see  later,  Quantitative  Analysis),  by  which  means  the  silver  halogen  salt 
is  formed  directly  (Carius). 


8 


ORGANIC    CHEMISTRY 


Sulphur  also  may  be  detected  by  the  Carius  method,  the  substance  being  heated  in  a 
sealed  tube  with  fuming  nitric  acid,  and  the  sulphuric  acid  formed  from  the  sulphur  of  the 
organic  compound,  precipitated  with  barium  chloride;  or  by  heating  the  substance  with 
pure  sodium  peroxide,  a  sulphate  is  formed.  By  heating  the  substance  in  a  test-tube 
with  metallic  sodium  and  dissolving  the  mass  in  a  little  water  a  solution  of  sodium  sulphide 
is  obtained  which  blackens  a  piece  of  silver  foil  or  a  silver  coin. 

Phosphorus  and  other  elements  are  detected  by  the  Carius  method,  the  substance 
being  oxidised  with  fuming  nitric  acid  and  the  liquid  tested  for  the  corresponding  acid 
(phosphoric,  etc.). 

QUANTITATIVE  COMPOSITION  (ELEMENTARY  ANALYSIS).  Lavoisier  was 
the  first  to  devise  an  apparatus  for  analysing  organic  substances  by  burning  them  with 
oxygen  under  a  bell-jar ;  while  Gay-Lussac,  Thenard,  and  Berzelius  successively  improved 
this  process  by  burning  the  substance  in  presence  of  potassium  chlorate.  Gay-Lussac, 
however,  showed  that  certain  nitrogenous  substances  cannot  be  burned  with  the  chlorate, 
and  suggested  as  a  general  and  more  certain  oxidising  agent  cupric  oxide,  which  when  hot 
gives  up  its  oxygen,  transforming  the  carbon  and  hydrogen  of  any  organic  compound  into 
carbon  dioxide  and  water  respectively,  while  the  nitrous  compounds  are  reduced  to  free 
nitrogen  by  passing  the  products  of  combustion  over  red-hot  copper  turnings.  It  is, 
however,  to  Liebig  that  the  credit  is  due  of  rendering  this  method  of  organic  analysis 
simple  and  exact  and  of  devising  simple  and  ingenious  forms  of  apparatus  for  absorbing 
the  products  of  combustion.  Even  to-day—disregarding  improvements  in  combustion 
furnaces  and  modifications  of  the  absorption  apparatus — the  determination  of  carbon  and 
hydrogen  (the  oxygen  is  estimated  by  difference)  is  carried  out  by  what  is  virtually  the 
method  employed  by  Liebig.1 

1  The  method  most  commonly  used  is  as  follows  :  0-15  to  0-30  gram  of  the  substance  is 
weighed  in  a  small  porcelain  boat,  which  is  then  filled  with  powdered  cupric  oxide,  previously 
heated  to  redness  and  perfectly  dry  ;  the  boat  is  then  introduced  into  the  position  c  of  the  hard 
glass  combustion  tube  (Fig.  13),  this  being  70  to  90  cm.  long,  or  10  to  12  cm.  longer  than  the 
combustion  furnace,  which  is  heated  by  25  to  30  gas  flames  (Fig.  14). 


FIG.  13. 

a  =  5  cm.  free;  6  =  12  cm.  spiral  of  oxidised  copper  gauze;  c  —  8  to  10  cm.  for  the 
boat;  d  =  3  cm.  copper  spiral;  e  =  40  to  45  cm.  granulated  cupric  oxide;  /  =  3  cm. 
oxidised  copper  spiral  or  12  cm.  of  reduced  copper  spiral  for  nitrogenous  substances; 
g  =  5  cm.  free. 

The  other  parts  of  the  tube  are  reserved  for  the  previously  heated  copper  spirals  and  granu- 
lated cupric  oxide  (Fig.  13).  When  a  fresh  combustion  is  to  be  made,  all  that  it  is  necessary 
to  do  is  to  remove  the  spiral  b  and  the  boat  and  to  introduce  the  new  substance  into  the  tube, 
which  is  already  charged  in  d,  e,  and  /  and  is  not  allowed  to  cool  below  40°  to  60°. 


14. 


The  combustion  is  earned  out  in  the  furnace  shown  in  Fig.  14,  the  tube  being  clo-'ed  at  a 

with  a  good  cork  and  a  glass  tap  which  can  be  connected  at  will  with  a  gasometer  containing 

ir  or  one  containing  oxygen,  which  should,  however,  before  reaching  the  combustion  tube 

•ough  tubes  containing  potassium  hydroxide  to  remove  the  carbon  dioxide,  and  then 


COMBUSTION  9 

For  determining  carbon  and  hydrogen  in  nitrogenous  substances  the  above  method  is 
modified  only  by  inserting  in  the  combustion  tube,  in  place  of  the  spiral/  (Fig.  13),  one 
of  reduced  copper  gauze  l  about  15  cm.  long,  this  serving  to  fix  the  oxygen  from  the  oxides 
of  nitrogen  resulting  from  the  combustion  and  to  liberate  the  nitrogen,  which  passes 
unchanged  through  the  absorption  apparatus. 

If  the  substance  to  be  analysed  contains  sulphur  or  a  halogen,  the  combustion  is  made 
with  lead  chromate  in  place  of  the  granular  copper  oxide,  and  the  heating  is  more  gentle 
to  avoid  fusion  of  the  chromate.  By  this  means  the  sulphur  remains  fixed  in  the  tube 
as  lead  sulphate  and  the  halogens  as  halogen  salts  of  lead.  Halogens  may  also  be  fixed 
on  a  spiral  of  silver  foil  about  10  cm.  long  placed  at  /  (Fig.  13),  the  substance  being 
combusted  as  usual  with  cupric  oxide;  if  both  nitrogen  and  a  halogen  are  present  the 
copper  and  silver  spirals  are  used  together. 

A  new  apparatus,  which  admits  of  the  combustion  of  organic  substances  being  very 
rapidly  carried  out,  has  been  devised  by  Carrasco  and  Plancher  (1 904-1 906)  .2 


through  drying  tubes  containing  calcium  chloride.  At  the  other  end  the  combustion  tube 
communicates  at  b,  first  with  a  tared  tube,  c,  containing  granulated  calcium  chloride  to  absorb 
the  water  formed  during  combustion ;  then  follows  the  tared  apparatus,  d,  containing  potassium 
hydroxide  solution  (30  to  35  per  cent.),  which  absorbs  the  carbon  dioxide  from  the  burnt  substance 
and  is  furnished  with  a  calcium  chloride  tube  to  retain  the  moisture  given  off  by  the  potassium 
hydroxide  solution.  Finally  follows  a  calcium  chloride  tube,  e,  which  is  not  weighed,  and  prevents 
moisture  entering  the  apparatus  from  the  air. 

Before  the  combustion  is  started  the  apparatus  is  tested  to  ascertain  if  it  is  perfectly  air- 
tight. This  is  done  by  closing  the  tap  a,  and  sucking  into  e  eight  or  ten  bubbles  of  gas ;  the 
slight  rarefaction  produced  in  the  interior  of  the  combustion  tube  causes  the  potash  solution  to 
rise  in  the  first  large  bulb  to  a  level  which  should  remain  constant  for  some  minutes.  The 
burners  at  the  end  6  are  then  gradually  lighted  until  the  portion /and  almost  all  of  the  portion  e 
are  heated  to  redness.  The  spiral  b  is  then  gradually  heated  from  the  a  end,  the  heating  being 
gradually  extended  under  the  boat  so  that  the  substance  is  completely  burnt.  During  the 
combustion  bubbles  of  air  are  passed  into  the  tube  from  the  gas-holder  so  as  to'  transport  the 
gases  produced  into  the  absorption  apparatus ;  during  the  last  ten  to  fifteen  minutes  a  gentle 
current  of  oxygen  is  passed  through,  and  then  the  flames  are  extinguished  and  air  again  passed 
for  ten  to  fifteen  minutes.  In  this  way  all  the  gases  from  the  combustion  are  removed  from  the 
combustion  apparatus  and  the  copper  oxide  is  completely  reoxidised,  so  that  the  tube  is  ready 
for  the  next  combustion. 

The  increases  in  the  weights  of  the  potash  and  calcium  chloride  apparatus  give  the  amounts 
of  carbon  dioxide  and  water  respectively  formed  during  the  combustion,  and,  since  44  parts  of 
carbon  dioxide  correspond  with  12  parts  of  carbon  and  18  parts  of  water  with  2  of  hydrogen, 
the  quantities  or  percentages  of  carbon  and  hydrogen  in  the  substance. can  be  calculated.  The 
sum  of  these  two  percentages,  when  subtracted  from  100,  gives  that  of  the  oxygen,  excepting 
where  the  substance  contains  nitrogen,  which  is  determined  directly  by  methods  given  later. 
In  this  way  the  percentage  composition  is  determined. 

1  The  reduction  is  effected  in  a  separate  glass  tube,  through  which  a  current  of  hydrogen 
is  passed  while  the  spirals  are  heated ;  when  the  copper  has  assumed  its  characteristic  red  colour, 
the  flames  are  extinguished  and  the  spirals  allowed  to  cool  in  the  current  of  hydrogen,  being 
afterwards  kept  in  desiccators  ready  for  use;  or,  better,  when  reduction  is  complete  and  the 
spirals  are  still  hot,  the  tube  is  exhausted  and  is  kept  so  until  cold,  so  as  to  avoid  the  danger  of 
hydrogen  remaining  occluded  by  the  copper. 

2  It  consists  of  a  small  external  combustion  tube,  c  (Fig.  15),  of  hard  glass,  and  about  20  cm. 
long  and  2  cm.  wide,  and  slightly  expanded  at  the  lower  closed  end.     The  tube  is  closed  at  the 
top  by  a  rubber  stopper,  /,  through  which  passes  a  porcelain  tube,  e,  wound   round  with  an 
electric  re-istance  formed  of  platinum -iridium  wire,  d;  along  the  interior  of  the  porcelain  tube 
passes  a  thick  silver  wire,  which  starts  from  d,  the  negative  pole,  and  ends  in  a  small  platinum 
wire  loop  and  serves  to  convey  the  current  (3  amps,  at  20  volts).     The  oxygen  for  the  combustion 
traverses  OS  and  the  upright  tube  of  the  stand,  and  passes  through  the  porcelain  tube  to  the 
bottom  of  the  combustion  tube.     In  the  stopper,  /,  is  fastened  a  piece  of  nickel  tube,  b,  which 
is  united  to  the  +  pole  and  to  the  platinum  spiral,  d,  and  serves  at  the  same  time  for  the  escape 
of  the  gases  formed  by  the  combustion  to  the  tube  r.     The  gases  are  absorbed  by  the^usual  tared 
apparatus  (u  =  calcium  chloride,  p  =  concentrated  potassium  hydroxide  solution),  but  with 
nitrogenous  or  halogenated  substances  the  gases  are  first  passed  through  a  U-tube  containing 
lead  dioxide  heated  to  180°  by  means  of  a  small  furnace,  ra.     The  connections  a  and  b  are  insu- 
lated from  one  another  by  porcelain  and  rubber.     When  the  current  passes  through  the  resistance 
the  glass  tube  is  heated  to  redness,  and  the  substance  (0-12  to  0-20  gram),  mixed  with  cupric 
oxide  or,  better,  with  platini.«ed  porous  porcelain  powder,  and  placed  at  the  bottom  of  the  glass 
tube,  is  burned  by  heating  the  outside  of  the  tube  directly  with  a  bunsen  flame.     The  combustion 
is  very  soon  completed,  the  platinum -iridium  spiral  apparently  accelerating  the  oxidation  cata- 
lytically ;  apart  from  the  time  occupied  by  the  weighings,  this  method  requires  fifteen  to  twenty 
minutes,  and  usually  gives  good  results.     For  the  analysis  of  fairly  volatile  liquids  or  of  sub- 
stances which  readily  sublime,  the  lower  part  of   the   combustion  tube  is  drawn  out  almost 


10 


ORGANIC    CHEMISTRY 


An  electrical  method  for  determining  carbon,  hydrogen,  and  sulphur  in  organic  substances 
was  also  proposed  by  Morse  and  Gray  in  America  in  1906. 

QUANTITATIVE  DETERMINATION  OF  NITROGEN.  (1)  Dumas'  Method. 
The  nitrogenous  organic  substance  (0-2  to  0-3  gram)  is  heated  in  a  hard  glass  tube  similar 
to  that  shown  in  Fig.  13,  but  closed  at  the  end,  a.  The  portions  a  and  b  contain  sodium 
hydrogen  carbonate  or  magnesium  carbonate;  between  b  and  c  is  placed  a  small  plug  of 
copper  gauze,  in  c  granulated  copper  oxide,  and  in  d  powdered  copper  oxide.  Then  follows 
a  space  10  cm.  in  length  in  which  is  placed  the  substance  to  be  analysed,  this  being  weighed 
and  mixed  with  powdered  cupric  oxide ;  next  comes  granulated  cupric  oxide,  and  in  / 
a  spiral  of  reduced  copper,  10  to  12  cm.  long.1 

The  extremity,  g,  of  the  tube  is  connected  by  means  of  a  gas  delivery  tube  with  a 
graduated  tube  (25  or  50  c.c.)  placed  upside  down  in  a  basin  of  mercury  and  filled  half 
with  mercury  and  half  with  concentrated  potassium  hydroxide  solution.  This  graduated 
tube  may  have  the  form  devised  by  Dumas  and  shown  in  Fig.  16;  the  gas  from  the  com- 
bustion tube  passes  into  the  tube  a,  furnished  with  a  clip,  m,  thence  through  a  little  mercury 
in  the  bottom  of  the  tube  b,  which  is  filled  with  potassium  hydroxide  solution  and  is  in 
communication  with  a  reservoir,  c,  of  this  solution.2 


horizontally,  and  the  substance  is  mixed  with  platinised  porcelain  powder  (2  to  3  per  cent, 
of  platinum);  liquids  may  also  be  heated  in  a  separate  tube  and  the  vapour  then  injected  into 
the  combustion  tube. 


FIG.  15. 

1  In  this  case  the  copper  spiral  may  be  rapidly  reduced  by  heating  it  over  a  large  non-luminous 
gas  flame  and  dropping  it  into  a  thick-walled  test-tube  containing  -J-  c.c.  of  ethyl  or,  better, 
methyl  alcohol;  the  tube  is  immediately  closed  by  a  rubber  stopper  through  which  passes  a 
glass  tube.     The  latter  is  connected  with  a  pump  until  the  spiral  is  cold. 

2  The  operation  is   begun   by   heating  the  combustion  tube  at  the  point  whore  the  mag- 
nesium carbonate  lies ;   the  carbon  dioxide  thus  evolved  expels  the  air  from  the  apparatus  into 
b,  whence  it  is  driven  by  raising  the  reservoir,  c,  and  opening  the  cock  at  the  top  of  b.    The 


KJELDAHL'S     METHOD 


11 


When  several  determinations  of  nitrogen  are  to  be  carried  out  the  procedure  is  some- 
times simplified  by  using  a  combustion  tube  open  at  both  ends,  like  that  of  Fig.  13,  the 
magnesium  carbonate  or  sodium  bicarbonate  being  omitted  and  the  combustion  tube 
being  connected  at  a  with  a  small  Kipp's  apparatus  for  the  evolution  of  carbon  dioxide 
(marble  and  hydrochloric  acid),  care  being  taken  to  free  the  apparatus  from  all  air  by  a 
prolonged  current  of  carbon  dioxide. 

(2)  KjeldahVs  Method  (Dyer's  modification).  0-5  to  1  gram  of  the  substance  is  placed 
in  a  hard  glass  flask  (200  to  300  c.c.)  with  a  long  neck,  into  which  penetrates  the  stem  of  a 
funnel  used  to  cover  the  flask  (Fig.  17).  «!20  c.c.  of  concentrated  sulphuric  acid  (66°  Be.)  and 
a  drop  of  mercury  (which  acts  as  a  catalytic  oxidising  agent)  are  added,  and  the  contents 
of  the  flask  are  heated,  at  first  gently  and  finally  more  strongly,  until  vigorous  boiling 
sets  in.  10  grams  of  potassium  sulphate  are  then  added,  a  little  at  a  time,  the  heating 
being  continued  until  the  liquid  is  decolorised,  by  which  time  the  whole  of  the  nitrogen  is 
transformed  into  ammonium  sulphate.  After  the  flask  has  been  allowed  to  cool,  its 


FIG.  16. 


FIG.  17. 


contents  are  washed  out  with  water  into  a  flask  already  containing  200  to  300  c.c.  of  water. 
3  to  4  grams  of  zinc  dust  (which  decomposes  ammoniacal  compounds  of  mercury  and 
prevents  bumping  by  the  evolution  of  hydrogen)  are  then  added,  and  the  flask  closed  with 

carbon  dioxide  is  absorbed  by  the  potash  solution,  and  when  no  more  air  collects  in  b  the  mag- 
nesium carbonate  is  no  longer  heated.  The  copper  spiral  and  the  copper  oxide  are  now  gradually 
heated  in  the  same  way  as  for  the  estimation  of  carbon  and  hydrogen,  the  heating  being  slowly 
extended  until  it  reaches  the  substance  itself.  Oxides  of  nitrogen  are  decomposed  by  the  copper 
spiral,  so  that  all  the  nitrogen  is  evolved  in  the  free  state  and  collects  in  b.  Finally  the  nitrogen 
remaining  in  the  combustion  tube  is  driven  into  b  by  means  of  carbon  dioxide  formed  by  again 
heating  the  magnesium  carbonate. 

At  the  end  of  the  operation,  in  order  to  measure  the  nitrogen,  a  graduated  tube  filled  with 
water  is  inverted  over  d,  and  the  cock  at  the  top  of  b  having  been  opened,  the  reservoir,  c,  is 
raised  until  all  the  gas  passes  into  the  graduated  tube.  The  latter  may  then  be  removed  to  a 
large  cylinder  full  of  water  and  when,  after  a  few  minutes,  the  gas  has  assumed  the  temperature 
of  the  water  (shown  by  an  accurate  thermometer)  the  tube,  grasped  by  a  clip  (the  hand  would 
warm  it),  is  arranged  so  that  the  level  of  the  liquid  inside  it  coincides  with  that  outside,  and  the 
volume  (v)  of  the  gas  read  off.  At  the  same  time  the  atmospheric  pressure  (b)  is  read,  and  the 
exact  temperature  (/)  of  the  water.  The  percentage  of  nitrogen  (p)  in  the  substance  is  then 
calculated  by  means  of  the  following  formula  : 


P 


«M&-  10).  0-12511 
V.  760(1  +  0-003677<)' 


where  s  indicates  the  weight  of  substance  taken,  w  the  pressure  of  water  vapour  expressed  in 
mm.  of  mercury  (see  Vol.  I.,  p.  35),  and  0-0012511  gram  the  weight  of  1  c.c.  of  moist  nitrogen  at  Oc 
and  760  mm.  (Rayleigh  and  Ramsay). 


ORGANIC    CHEMISTRY 


a  rubber  stopper  through  which  pass  a  tapped  funnel  containing  120  to  160  c.c.  of  con- 
centrated sodium  hydroxide  solution  (30  to  35  per  cent.)  and  a  glass  bulb  (Figs.  18  and  19) 
communicating  with  a  simple  condensing  tube  dipping  into  a  flask  containing  a  measured 
volume  of  standard  sulphuric  acid  and  a  drop  of  methyl  orange.  In  order  to  prevent 
spurting  of  the  caustic  soda  and  its  introduction  into  the  condenser  tube,  the  glass  bulb 
is  fitted  with  a  delivery  tube  curved  towards  the  wall  of  the  bulb ;  it  is,  however,  as  well 
to  push  into  this  tube,  almost  as  far  as  the  bulb,  a  small  plug  of  glass-wool  or  asbestos. 
Solutions  of  soda  more  concentrated  than  35  per  cent,  often  lead  to  spurting.  About  one- 
half  of  the  liquid  is  distilled  and  the  excess  of  sulphuric  acid  remaining  in  the  collecting 
flask  determined  by  titration  with  alkali.  Hence  the  amount  of  ammonia  fixed  by  the 
acid  may  be  calculated  and  so  the  percentage  of  nitrogen  in  the  substance  analysed.  In 
Figs.  17  and  19  are  shown  forms  of  apparatus  with  which  it  is  possible  to  carry  out  several 
determinations  simultaneously. 

Kjeldahl's  method  cannot  be  used  as  it  stands  for  the  analysis  of  organic  substances 
which  contain  nitrogen  either  united  to  oxygen  (nitro-compounds)  or  forming  part  of  a 
pyridine  or  similar  nucleus  (quinoline,  etc.).  In  such  cases  the  method  is  modified  as 
described  under  Aromatic  nitro-derivatives  (Part  III). 


FIG.  18. 


FIG.  19. 


(3)  Will  and  Varrentrapp's  Method.  This  method  is  based  on  the  principle  that  almost 
all  nitrogenous  organic  substances  (which  do  not  contain  nitrogen  linked  to  oxygen,  such 
as  the  nitro-compounds),  when  they  are  heated  with  an  alkali  hydroxide  or,  better,  with 
soda-lime  (see  Vol.  I.,  p.  618),  yield  hydrogen,  which  transforms  the  nitrogen  into  ammonia. 
Little  use  is  made  of  this  method  to-day. 

QUANTITATIVE  DETERMINATION  OF  THE  HALOGENS.  The  method  most 
commonly  used  is  that  of  Carius.  The  substance  (0-15  to  0-2  gram)  is  weighed  out  in  a 
small  tube,  which  is  then  introduced  into  a  large,  hard  glass  tube  30  to  40  cm.  long  and 
2  to  3  cm.  wide,  closed  at  one  end  and  containing  about  2  c.c.  of  fuming  nitric  acid  and 
about  0-5  gram  of  solid  silver  nitrate ;  this  introduction  is  effected  in  such  a  way  that  the 
acid  does  not  enter  the  small  tube.  The  large  tube  is  then  softened  near  the  open  end  by 
heating  in  the  blow-pipe  flame  and  gradually  drawn  out  to  a  point  (Fig.  20,  A),  the  walls 
of  the  tube  being  allowed  to  thicken  during  the  fusion  (Fig.  20,  B,  shows  the  upper  part 
of  the  tube  on  a  larger  scale) .  After  being  allowed  to  cool  in  a  vertical  position,  the  tube 
is  introduced  into  a  thick- walled  iron  sheath,  which  is  closed  with  a  screw-cap.  It  is  then 
safe  to  incline  the  tube  and  introduce  it  into  a  bomb-furnace  (Fig.  21),  which  holds  four 
or  more  tubes  and  is  raised  slightly  at  one  end ;  this  is  heated  for  4  to  6  hours,  the  tem- 
perature being  raised  gradually  to  about  250°.  Sometimes  the  tubes  burst  owing  to  the 
great  internal  pressure,  but  without  danger  from  flying  fragments  of  glass  owing  to  the 
protection  of  the  iron  sheaths  and  of  the  folding  shutters  at  the  ends  of  the  furnace,  these 
being  lowered  during  the  heating. 

At  the  end  of  the  operation,  when  the  tube  is  cool,  it  is  taken  from  the  iron  sheath, 
held  in  a  vertical  position,  and  its  point  (Fig.  20,  A  a)  softened  in  a  bunsen  flame.  When 
the  pressure  in  the  tube  has  been  thus  relieved,  a  scratch  is  made  with  a  file  at  the  point 
marked  b,  and  the  file-mark  touched  with  a  red-hot  glass  rod,  with  the  result  that  the  upper 
part  of  the  tube  breaks  off.  The  tube  is  then  carefully  emptied  and  washed  out  into  a 


CALCULATION     OF    FORMULAE 


13 


beaker  with  water,  the  small  tube,  held  in  pincers  or  a  piece  of  platinum  wire,  being  well 
washed  inside  and  outside  before  removal.  The  liquid  is  heated  and  the  precipitated  silver 
halogen  compound  is  then  collected  on  a  filter,  washed,  dried  in  an  oven,  detached  from 
the  filter  and  heated  in  a  weighed  porcelain  crucible  until  it  just  begins  to  melt.  After 
being  allowed  to  cool  in  a  desiccator,  the  crucible  is  weighed  and  the  amount  of  halogen 
contained  in  the  organic  substance  calculated  from  the  weight  of  silver  haloid. 

QUANTITATIVE  DETERMINATION  OF  SULPHUR  AND  PHOSPHORUS. 
This  is  carried  out  by  the  Carius  method  in  the  same  way  as  for  halogens,  except  that 
no  silver  nitrate  is  introduced  into  the  tube.  At  the  end  of  the  heating,  the  sulphur  is 
obtained  as  sulphuric  acid  or  the  phosphorus  as  phosphoric  acid,  estimation  of  the  amounts 
of  these  acids  being  effected  by  the  ordinary  methods.  The  halogens,  sulphur  and  phos- 
phorus, may  also  be  determined  after  fusion  of  the  substance  with  pure  sodium  peroxide. 

CALCULATION  OF  THE  EMPIRICAL  FORMULA.  From  the  results 
of  the  elementary  analysis  of  an  organic  substance  may  be  calculated  the 
percentage  composition,  i.  e.,  the  quantity  of  each  component  in  100  parts  of 


—     b 


A 

1 

A 


FIG.  20. 


FIG.  21. 


substance.  To  deduce  the  chemical  formula,  that  is,  the  proportions  in  which 
the  different  atoms  enter  into  the  molecule,  the  percentage  weight  of  each 
component  is  divided  by  the  corresponding  atomic  weight,  the  numbers  thus 
obtained  giving  the  proportions  between  the  numbers  of  atoms  of  the  different 
elements. 

These  numbers  sometimes  give  directly  the  numbers  of  atoms  contained 
in  the  molecule,  but  in  other  cases  they  represent  multiples  or  submultiples  of 
the  real  numbers  of  atoms. 

If,  for  example,  lactic  acid  is  analysed,  the  percentage  composition  is  found 
to  be  :  C,  40  per  cent. ;  H,  6'6  per  cent. ;  0,  53 "4  per  cent. ;  by  dividing  these 
numbers  by  the  corresponding  atomic  weights,  the  following  numbers  are 
obtained:  C,  3'3  (i.e.,  £?);  H,  6'6  (G-j?) ;  and  0,  3'3(5-2?4).  These  proportions 
have  a  common  factor,  33,  and  division  by  this  gives  1C,  2H,  and  10,  i.  e., 
CH2O,  which  is  an  empirical  or  minimum  formula,  the  simplest  formula  express- 
ing the  proportions  between  the  numbers  of  atoms  of  the  different  elements. 

This  minimum  formula  does  not,  however,  represent  the  molecular  magni- 
tude, and,  in  fact,  analyses  of  formaldehyde,  acetic  acid,  grape  sugar,  etc., 
give  the  same  percentage  composition  and  the  same  minimum  formula,  CH2O, 
which  must  hence  be  a  submultiple  of  the  formulae  of  these  substances. 


14  ORGANIC    CHEMISTRY 

A  knowledge  of  the  percentage  composition  is  not  sufficient  to  determine 
the  true  molecular  formula;  the  molecular  magnitude,  i.e.,  the  molecular 
weight,  must  also  be  known  in  order  to  permit  of  a  choice  between  the  various 
multiples.  By  making  use  of  one  of  the  methods  described  in  Vol.  I.,  "  In- 
organic Chemistry  "  (pp.  34  et  seq.),  the  molecular  weight  of  lactic  acid  is  found 
to  be  90,  so  that,  of  the  various  possible  formulse,  CH2O  (mol.  wt.  30),  C2H402 
(mol.  wt.  60),  C3H603  (mol.  wt.  90),  C4H8O4  (mol.  wt.  120)  ....  C6H1206 
(mol.  wt.  180),  etc.,  only  C3H603  corresponds  with  lactic  acid.  Even  this 
formula  and  the  empirical  formula,  however,  tell  nothing  concerning  the 
grouping  of  the  atoms  in  the  molecule  which,  as  is  explained  in  the  following 
pages,  is  given  by  the  constitutional  formula. 

DETERMINATION   OF  THE   MOLECULAR   WEIGHT   BY 
CHEMICAL  MEANS 

In  lactic  acid  one-sixth  of  the  hydrogen  may  be  substituted  by  a  metal,  so  that  there 
must  be  at  least  six  (or  a  multiple  of  six)  atoms  of  hydrogen  in  the  acid,  the  empirical 
formula  being  necessarily  at  least  trebled,  giving  C3H603.  To  ascertain  if  this  is  the  true 
formula,  a  derivative  of  the  acid  is  prepared,  such  as  the  silver  salt,  which  may  easily  be 
obtained  pure.  Analysis  of  this  salt  shows  it  to  contain  54-8  per  cent,  of  silver,  and  the 
atomic  weight  of  silver  being  107-7,  calculation  indicates  that  the  residue  of  the  lactic 
acid  combined  with  107-7  parts  of  silver  weighs  89.  Assuming  that  only  1  atom  of 
silver  has  entered  the  lactic  acid  in  place  of  1  of  hydrogen  (as  may,  indeed,  be  deduced 
from  the  fact  that  the  quantity  of  hydrogen  in  the  salt  is  five-sixths  of  that  originally 
present  in  the  acid),  the  weight  of  the  lactic  acid  would  be  89  -f  1,  or  90.  The  true 
formula  of  the  acid  would  hence  be  that  corresponding  with  a  molecular  weight  of  90, 
».  e.,  C3H603. 

For  acid  substances  in  general  this  cJiemical  method  may  be  employed  for  determining 
the  molecular  weight,  making  use  of  the  silver  salt  and  determining  if  the  acid  is  mono-, 
di-,  or  tri-basic  (that  is,  ascertaining  if  the  silver  replaces  1,  2,  or  3  atoms  of  hydrogen), 
the  calculation  being  then  based  on  the  presence  of  1,  2,  or  3  atoms  of  silver  in  the 
salt. 

For  basic  substances,  the  molecular  magnitude  may  be  determined  chemically  by 
analysing  the  platinichlorides,  the  formulae  for  which  are  always  of  the  type  of  that  of 
ammonium  platinichloride  :  PtCl4(NH3-HCl)2,  the  ammonia  being  replaced  by  the  organic 
base,  which  is  mono-  or  di-acid,  according  as  it  replaces  one  or  two  molecules  of  ammonia 
in  the  platinichloride. 

For  other  (indifferent)  organic  substances  derivatives  are  prepared  by  substituting 
chlorine  atoms  for  one  or  more  hydrogen  atoms,  the  proportion  of  chlorine  being  then 
estimated ;  the  calculation  is  then  similar  to  that  described  above. 

The  chemical  method  for  determining  the  molecular  magnitude  does  not  always  give 
certain  results  :  experimental  difficulties  sometimes  occur  and  often  entail  great  labour. 
Consequently  the  determination  of  molecular  weights  is  usually  effected  by  physical  methods  : 
vapour  density  method,  cryoscopic  method,  ebullioscopic  method,  etc.,  these  being  all 
described  and  illustrated  in  Vol.  I.  (Part  I). 

POLYMERISM 

It  sometimes  happens  that  the  analysis  of  different  substances  shows  them 
to  have  the  same  percentage  composition,  although  their  chemical  and  physical 
properties  are  different ;  thus,  for  example,  acetic  acid,  lactic  acid,  glucose,  etc., 
contain  the  same  elements,  C,  H,  and  O,  in  the  same  proportions,  there  being 
2n  hydrogen  atoms  and  n  oxygen  atoms  for  n  carbon  atoms.  Accurate 
study  of  these  compounds  and  determination  of  the  molecular  magnitude 
(molecular  weight)  show  that  the  differences  depend  on  the  true  formulae 
being  multiples  of  the  minimum  or  empirical  formula.  Thus,  whilst  the 
molecule  of  acetic  acid  is  represented  by  C2H4O2,  that  of  lactic  acid 


RADICLES     AND     TYPES  15 

corresponds  with  C3H6O3,  and  that  of  glucose  with  C6H1206.  These  molecules 
are  hence  all  multiples  of  a  hypothetical  complex  CH2O,  the  ratios  (but  not  the 
absolute  quantities)  between  carbon,  hydrogen,  and  oxygen  being  the  same 
(1:2:1)  in  all  cases.  These  compounds  are  termed  polymerides  and  the 
phenomenon  is  known  as  polymerism. 

In  some  instances,  however,  it  happens  that  the  molecular  magnitude  is 
not  sufficient  to  differentiate  certain  compounds,  which,  besides  containing  the 
same  elements  in  the  same  proportions  (equal  percentage  compositions),  have 
also  the  same  molecular  magnitudes,  although  differing  in  their  physical  and 
chemical  properties.  To  explain  the  existence  of  these  isomeric  compounds, 
the  chemical  nature  of  carbon  must  be  studied  more  in  detail. 


VALENCY   OF  CARBON,   ISOMERISM,   AND 
CONSTITUTIONAL   FORMULA 

On  the  foundation  of  multivalent  radicles,1  discovered  by  Odling,  and 
of  the  investigations  of  Frankland  (1852),  which  showed  that  nitrogen, 

1  Theory  of  Radicles  and  Types.  In  the  first  twenty  years  of  last  century,  various  compounds 
were  discovered  which  stood  in  apparent  contradiction  to  the  electro-chemical  theory  of  dualistic 
formulae,  put  forward  by  Berzelius  (Vol.  I.,  p.  46);  in  fact,  in  certain  compounds  the  hydrogen 
(electro-positive)  was  replaced  by  chlorine  (electro-negative)  without  appreciably  changing  the 
chemical  characters  of  the  original  compounds.  It  was  then  that  chemical  compounds  came  to 
be  represented  by  unitary  formula,  no  account  being  taken  of  the  grouping  of  the  atoms  in  the 
molecule. 

Gradually,  however,  as  the  number  of  new  organic  substances  increased,  certain  analogies 
became  evident  in  their  chemical  behaviour.  In  studying  cyanogen  Gay-Lussac  (1815)  had 
indeed  met,  in  various  reactions  and  in  various  substances,  the  residue  or  radicle  CN,  which 
behaved  as  a  monovalent  element  (like  the  halogens),  combining  with  one  atom  of  different 
monovalent  metals,  etc.  In  1832  Liebig  and  Wohler  discovered  and  studied  a  monovalent 
atomic  group  or  radicle,  benzoyl,  C7H60,  which  was  found  in  oil  of  bitter  almonds  combined  with 
an  atom  of  hydrogen  (C7H60);  on  oxidation  by  the  air,  this  essence  became  transformed  into 
benzoic  acid,  C7H602,  which  with  PC15  gave  benzoyl  chloride,  C7H5OC1,  and  this,  in  its  turn,  gave 
the  aldehyde  C7H60,  when  treated  with  nascent  hydrogen,  or  benzoic  acid  under  the  action  of 
water.  All  these  compounds  contain  the  monovalent  benzoyl  nucleus,  C7H50,  which  passes 
unchanged  from  one  to  the  other  by  combining  with  monovalent  atoms  or  groups.  In  1833, 
in  a  classic  work,  Bunsen  studied  another  radicle,  cacodyl,  which  is  a  monovalent  organic  arsenic 

/-ITT 

residue,  As<pTT3 .  Later,  in  1837,  Dumas  advanced  and  developed  the  theory  of  radicles,  study- 
ing and  classifying  organic  compounds  with  reference  to  the  different  radicles  contained  in  them, 
these  radicles  thus  coming  to  be  considered  almost  as  the  elementary  substances  of  organic  chemistry. 
The  condensation  of  simple  radicles  leads  to  a  compound  radicle,  forming  a  complex  which  can 
unite  with  other  atoms  or  atomic  groups.  Liebig  supported  this  new  theory,  whilst  Berzelius 
strenuously  opposed  it,  reproaching  Dumas  for  regarding  all  chemical  combinations  as  due  to 
reciprocal  interchanges  of  radicles. 

Dumas  and,  still  more  so,  Laurent,  as  a  consequence  of  the  discovery  of  new  substances, 
arrived  logically  at  the  theory  of  substitution,  which  assumed  the  possibility  of  replacing,  one  by 
one,  the  elements  forming  the  radicle  or  nucleus  of  certain  compounds  by  other  elements  or  by 
radicles  of  other  compounds  (Dumas  termed  this  phenomenon  of  substitution  metalepsy). 

Not  only  the  hydrogen  and  oxygen,  but  also  the  carbon  of  the  radicles  could,  according 
to  Laurent,  be  replaced  by  other  radicles  or  other  elements,  e.  g.,  by  chlorine,  without  the 
fundamental  characters  of  the  original  substances  being  substantially  changed. 

These  last  consequences  of  the  theory  of  substitution  in  radicles  (Dumas)  or  in  nuclei  (Laurent) 
were  combated  not  only  by  Berzelius,  but  even  by  Liebig,  who  attempted  to  cover  these  new 
conceptions  with  ridicule  and  published  in  his  "  Annalen  "  (1840)  a  pungent  satire  in  the  form 
of  a  letter  from  Paris  which  was  signed  "  S.  C.  H.  Windier  "  (Schwindler  being  the  German  for 
swindler  ! ),  and  which  made  the  astonishing  statement  that  it  had  been  found  possible  to  replace 
all  the  atoms  of  the  molecule  of  manganese  acetate  by  the  corresponding  number  of  chlorine 
atoms,  the  resulting  substance  retaining  the  characters  of  the  original  salt,  although  formed  of 
chlorine  alone;  further,  on  the  basis  of  the  new  theory,  it  was  concluded  that  the  chlorine  used 
in  England  to  bleach  textiles  replaced  the  hydrogen,  oxygen,  and  carbon,  and  that  already  chlorine 
was  being  spun  for  the  manufacture  of  nightcaps,  which  were  greatly  appreciated  ! ! 

Nevertheless,  the  new  conceptions  triumphed  with  the  aid  of  numerous  discoveries,  which 
served  to  confirm,  more  and  more,  the  ideas  of  Laurent  and  Dumas.  Moreover,  with  the  studies 
of  Gerhardt,  new  horizons  were  opened  to  organic  chemistry,  which  for  so  many  years  found  a 
solid  basis  in  Laurent  and  Gerhardt's  (1852)  theory  of  types,  this  clearing  up  the  nebulous  ideas 
then  still  held  on  the  atom  and  the  molecule,  and  it  is  due  to  these  two  investigators  that 


16  ORGAN  1C    CHEMISTRY 

phosphorus,  and  other  elements  easily  form  compounds  with  three  or  five 
equivalents  of  other  elements,  Kekule,  in  1857  and  1858,  accurately  developed 
the  true  conception  of  valency,  showing  the  constant  tetra  valency  of  carbon  and 
thus  widening  the  horizon  of  organic  chemistry  and  originating  the  remarkable 
theoretical  and  practical  development  of  the  past  half-century. 

Kekule  and,  independently  of  him,  Cooper  brought  to  light  another  most 
important  property  of  carbon,  resulting  from  its  four  equivalent  valencies; 
they  showed  that  carbon  atoms  possess  also  the  property  of  combining  directly 
one  with  another,  in  a  greater  or  less  number,  mutually  saturating  one,  two, 
or  even  three  valencies  and  forming  varying  chemical  compounds.  For 
convenience,  we  represent  these  compounds  graphically,  placing  the  carbon 
atoms  in  an  open  or  closed  chain  and  saturating  the  valencies  remaining  free 
with  other  elements  (usually  hydrogen  and  oxygen).  We  have  thus  a  series 
of  groups  differing  according  as  the  atoms  united  in  a  chain  are  few  or  many 
(even  more  than  30),  according  to  whether  the  chain  is  branched  by  means 
of  lateral  chains,  and  also  according  as  the  valencies  saturated  between  carbon 
and  carbon  are  1,  2,  or  3. 

•If  we  represent  the  valencies  of  carbon  by  strokes,  the  valencies  of  the  different  carbon 
atom  chains  are  given  by  the  numbers  of  free  valencies  which  are  not  used  in  uniting  the 

Avogadro's  work,  denied  by  everybody,  finally  assumed  the  important  position  accorded  to 
it  in  modern  chemistry. 

All  organic  and  inorganic  compounds  were  explained  by  comparing  them  with  simple  types 
of  inorganic  substances  of  well-known  constitutions.     The  fundamental  types  of  Gerhardt  were 

TT  ^ 
four  in  number  :    §j,   JJ},   §]o,    :  [    N. 

It  was  supposed  that  all  the  principal  chemical  compounds  then  known  were  derived  from  these 
types  by  simple  substitution  of  the  hydrogen  by  other  elements  and  radicles.     From  the  first 

type  may  be  derived,  for  example  :   hydrocyanic  acid,     £1  }  ',  ethane,     2  j|  !  ;   ethyl  cyanide, 
pvr[.  etc.;  from  the  second,  sodium  chloride,   ™     ;  ethyl  chloride,     2  nf  1  5  acetyl  chloride, 


™     ;   ey    co,        n 

2    %  I  ;  and  so  on.     With  the  third  type  correspond,  for  example,  sodium  hydroxide,    £  j  0  ; 
nitric  acid,  N^J)O;    acetic    acid,  CsH8jjj();    nitric    anhydride,  ^CM0'    acetic   anhydride, 


jjj    \  o     , 
C2H3OJ  °>  etc' 

From  the  fourth  type,  Hofmann  and  Wurtz  deduced  theoretically  and  prepared  in  the  labora- 
tory a  large  number  of  compounds,  part  or  all  of  the  hydrogen  atoms  of  ammonia  being  replaced  ; 

C2H5)  C2H5|  CH3| 

for  example,  ethylamine,       H  rN  ;  diethylamine,  G2H5  •  N  ;  trimethylamine,  CH3  >  N  ;  acetamide, 
Hj  H)  CH 


H  IN,  etc. 


To  explain  the  existence  of  polybasic  acids  and  various  other  substances,  Odling,  Williamson, 
and  Kekule  had  recourse  to  the  idea  of  multiple  types,  sulphuric  acid  being  regarded  as  derived 

HQ  H)Q 


from  the  double  water  type,  TT{     ,  thus  S02  j-^,  and  similarly  succinic  acid,  C4H4O2  -Q,  etc.; 

H  }  °  HJ  - 

for  glycerol  a  triple  type  was  assumed,  and  so  on. 

Hl 
H  I 

In  1856  Kekul6  introduced  another  very  important  type,  that  of  marsh  gas,  jj  VC,  with 

HJ 

tetra  valent  carbon,  to  which  he  referred  numerous  organic  compounds  ;  also  certain  compounds 

PTT  i  NH2"| 

3  H 

may  be  referred  both  to  marsh  gas  and  to  ammonia,  for  example,  methylamine,  H  -N,  or        r  >  C, 

H'          nj 

and  from  these  different  methods  of  considering  the  constitution  and  the  reference  to  different 
types,  were  deduced  various  processes  for  preparing  one  and  the  same  compound  from  different 
starting  materials. 


ISOMERISM  17 

carbon  atoms  among  themselves  and  which  can  be  saturated  by  different  elements  (usually 
H,  O,  N),  giving  rise  to  an  enormous  number  of  organic  compounds.1 

The  physical  and  chemical  differences  of  these  compounds,  termed  isomerides, 
are  explained  by  the  different  grouping  or  linking  of  the  atoms  in  the  molecule. 
In  their  chemical  transformations,  isomerides  give  up  or  exchange  quite  different 
atomic  groups  or  atoms,  owing  to  the  different  functions  and  positions  occupied 
by  these  atoms  or  groups  in  the  molecule. 

The  first  cases  of  isomerism  were  discovered  by  Berzelius  in  1833  during 
an  investigation  of  racemic  acid. 

It  is  hence  not  sufficient  to  represent  organic  compounds  by  an  empirical 
molecular  formula,  the  structural  or  constitutional  formula,  deducible  from 
the  graphic  representation  of  the  chains  illustrated  above,  being  necessary 
in  many  cases  to  distinguish  between  isomerides. 

To  decide  which  of  two  isomeric  formulae  should  be  assigned  to  a  given 
substance,   various  chemical  reactions  are  carried  out  with  the  substance, 
study  of  the  resultant  new  products  indicating  the  constitutional  formula.2 
1  The  following  are  some  of  these  hypothetical  carbon  atom  chains  : 

C^  C/              &-             C/ 

C^              C<                 C-              |\  ||  \              HI                  II  x 

(1)        I);     (2)      ||>;        (3)    ||j        ;     (4)  C=  ;  (5)    C_;  (6)    C     ;  (7)     C     ; 

Cf               C/                  C—               |/  |/               \,               \\/ 

C(-  C/              C/              C/ 

Hexavalent        Tetravalent          Divalent  \  \  \  .  \ 


A 

° 


\ 

C=  C  —  C        C— 

(8)  ;  (9)     —  C-C£-,etc.  (10)  (11)       ||          |      ; 

C-  -C<=V-   ; 

\/         < 


i    A 

°° 


>C   C<        —  C   C—      —  C   C   C— 
(13)   I    I   ;   (14)    I    ||   ;  (15)   |    ||    | 
>C   C<        —  C   C—      —  C   C   C 
\o/  \N/         \0/\0/ 

A  I    I 

Among  these  chains  are  two  (Nos.  8  and  9)  containing  four  carbon  atoms  and  having  equal 
numbers  of  free  valencies.  By  saturating  these  ten  free  valencies  with  ten  H  atoms  two  com- 
pounds are  obtained  (these  have  actually  been  prepared)  which  contain  equal  numbers  of  C  and 
H  atoms,  and  have  therefore  the  same  percentage  composition  and  the  same  molecular  weight. 

2  An  example  will  render  these  ideas  clear  :  It  is  found  that  ethyl  alcohol  (ordinary  liquid 
alcohol)  and  gaseous  methyl  ether  have  different  physical  and  chemical  properties,  although  they 
possess  the  same  percentage  composition  and  the  same  molecular  magnitude,  represented  by  the 
formula  C2H60.  The  constitutions  or  internal  molecular  structures  of  the  two  compounds  are 
determined  by  a  study  of  the  following  chemical  reactions  :  treatment  of  the  alcohol  with  hydro- 
chloric acid  gives  first  a  compound  C2H6C1  (ethyl  chloride),  one  atom  of  monovalent  chlorine 
having  replaced  one  atom  of  oxygen  and  one  of  hydrogen  or  a  hydroxyl  residue,  OH.  By  means 
of  nascent  hydrogen,  the  chlorine  atom  of  ethyl  chloride  may  be  replaced  by  a  hydrogen  atom, 
giving  the  compound  C2H6  (ethane).  These  reactions  are  hence  expressed  by  the  following 
equations  :  (1)'C2H5  •  OH  +  HC1  =  H20  +  C2H5C1;  (2)  C2H5C1  +  H2  =  HC1  +  C,H6;  ethane, 

H\          /'H 
however,  can  have  only  the  constitution,  H^C  —  C\-H,  i.  e.,  CH3  —  CH3,  so  that  the  alcohol  will 

H/          XH 
H\  /OH 

have  the  constitution  H-/C  —  C<—  H 
W  \H 

On  the  other  hand,  it  is  found,  by  various  reactions,  that  the  six  hydrogen  atoms  of  methyl 
ether  present  no  difference  one  from  another,  and,  no  matter  under  what  conditions  hydriodic 
acid  acts  on  the  ether,  it  eliminates  the  oxygen  as  water,  and  another  product  is  obtained  which 
contains  only  one  carbon  atom  in  the  molecule  :  The  reaction  hence  takes  place  according  to  the 
equation  : 


It  is  evident,  then,  that  in  methyl  ether  the  six  hydrogen  atoms  are  united  homogeneously 
VOL.  II.  2 


18  ORGANIC    CHEMISTRY 

Use  is  not  always  made  of  constitutional  formulae,  since  they  are  not  simple 
and  are  often  inconvenient  to  write;  hence  attempts  are  made  to  simplify 
them  by  indicating  the  more  important  groups  or  residues,  contained  in  the 
molecule  and  giving  at  the  same  time  an  idea  of  the  constitutions  and  of  the 
functions  of  these  groups ;  this  is  done  by  means  of  the  so-called  rational 
formula.  The  rational  formula  of  ethyl  alcohol  will  be  C2H5  •  OH,  in  which 
the  monovalent  OH  residue,  characteristic  of  all  the  alcohols,  is  separated; 
that  of  acetic  acid  will  be  CH3  •  COOH,  the  group  COOH  being  characteristic 
of,  and  common  to,  all  organic  acids,  etc. 

METAMERISM.  Constitutional  and  rational  formulse  explain  clearly 
isomerism  in  general  and  also  the  special  case  bearing  the  name  metamerism. 
When,  to  an  atom  of  a  polyvalent  element  are  united  one  or  more  groups  in 
their  different  isomeric  forms,  we  have  special  cases  of  isomerism  for  definite 
groups  of  substances.1 

PSEUDOISOMERISM,  TAUTOMERISM,  DESMOTROPY.  A  substance 
sometimes  contains  atomic  groups  that  occupy  a  very  precarious  (labile)  position, 
since  they  exert  certain  influences  one  on  the  other  and  under  given  conditions 
may  react  in  different  ways,  giving  now  one  new  substance  and  now  another ; 
this  explains  how  it  is  that  some  compounds  having  a  well-defined  chemical 
character  may,  under  some  conditions,  behave  like  substances  with  other 
chemical  characters,  without  it  being  necessary  to  assume  a  true  change  of 
constitution.  Thus,  for  example,  some  of  the  derivatives  of  cyanic  acid, 
CN  '  OH,  behave  like  derivatives,  sometimes  of  the  formula  N  =  C — OH  and 
sometimes  of  the  formula  NH  =  C  =  0,  when  the  hydrogen  atom  is  replaced 
by  a  given  radicle.  The  same  is  the  case  for  derivatives  of  cyanamide, 
N—  C — NH2,  and  of  carbodiimide,  NH  =  C  =  NH,  and  of  the  two  non- 

I  I 

nitrogenous  types,  -C(OH)  =  C  —  CO  —  and  —  CO  —  CH  -  CO— ,  where  a 

hydrogen  atom  oscillates  between  the  two  carbon  atoms.  These  compounds 
exist  usually  in  only  one  form,  the  more  stable  one,  but  in  the  derivatives 
this  stable  form,  simply  on  heating,  is  transformed  into  tbe  labile  one.  For 
this  phenomenon  Baeyer  proposed  the  name  pseudoisomerism,  and  others  that 
of  desmotropy ;  it  may  be  assumed  that  the  Other  isomeride  is  present  in 
minimal  quantity,  not  detectable  by  ordinary  reagents. 

These  forms  may  be  distinguished  sometimes  by  chemical  reactions,  but 
more  generally  by  the  molecular  refraction,  dielectric  constant,  magnetic 
rotation,  electrical  conductivity,  etc.  (Under  the  heading  Ethyl  acetoacetate, 
Knorr  and  Meyer's  method  for  separating  the  two  forms  is  described.) 

In  various  substances,  where  several  hydroxyls  are  present  in  more  or  less 

to  the  two  atoms  of  carbon  and  that  the  carbon  atoms  are  joined,  not  directly,  but  indirectly, 
by  means  of  an  oxygen  atom,  which  is  readily  eliminated.  The  constitutional  formula  of  methyl 
ether  will  hence  -be  : 

H\  /H 

H^C— 0— C^H    or    CH3— 0— CH3. 

H/  \H 

>C3H7 
r  For  example,  in  the  compound,  N\~  H     ,  the  monovalent  group  — C3H7  may  be  present  in 

/CH3 
its  isomeric  forms,  i.  e.,  either  as  — CH, — GEL— CH,  or  as  — C^H    •.     Although  there  is  con- 

\CH3 

siderable  resemblance  between  these  two  compounds,  their  different  constitutions  are  manifested 
in  certain  chemical  and  physical  properties.  The  following  compounds  are  also  metameric 

/CH3  XCH3 

isomerides  :  Nx-C2H5  and  N^— CH3  ;  in  fact,  although  the  percentage  compositions  and  molecular 

^CH3 

magnitudes  are  the  same  in  both  cases,  the  substituent  groups  of  the  ammonia  molecule  are 
different  and  the  compounds  belong  to  different  categories — disubstituted  and  trisubstituted 
ammonias. 


STEREOISOMERISM 


19 


adjacent  positions,  there  is  often  a  tendency  for  intramolecular  transformation 
to  take  place  with  condensation  of  two  of  these  groups  and  separation  of  a 
molecule  of  water,  giving  rise  to  isomeric  anhydrides,  ethers,  ketones,  or 
alcohols,  etc.  In  their  turn,  these  derivatives  or  isomerides,  which  may  be 
transformed  one  into  the  other,  give  rise  to  distinct  classes  of  compounds ; 
this  isomerism  is  called  tautomerism,  and  may  be  regarded  as  dynamic  rather 
than  static  isomerism. 

STEREOISOMERISM  OR  ISOMERISM  IN  SPACE.  We  have  already  seen  that, 
by  the  tetra valency  of  carbon  and  its  property  of  uniting  with  itself  to  form  various  chains, 
it  is  possible,  in  certain  cases,  to  explain  the  existence  of  isomerides,  which  have  the  same 
percentage  composition  and  molecular  magnitude,  but  different  groupings  within  the 
molecules.  Many  cases  of  isomerism,  foreseen  from  theoretical  considerations,  have 
since  been  actually  met  with  and  different  isomerides  have  been  prepared  artificially- 
after  their  existence  had  been  foretold. 

For  a  long  time,  however,  certain  compounds  were  known  for  which  ordinary  isomerism 
did  not  provide  any  explanation;  among  these  the  most  important,  from  an  historical 
point  of  view  also,  are  the  four  dihydroxysuccinic  acids  (tartaric  acids),  of  which  two 
(ordinary  tartaric  acid  and  racemic  acid)  were  studied  by  Berzelius  as  long  ago  as  1830. 
To  these  must  be  added  Isevo-rotatory  tartaric  acid  and  mesotartaric  acid,  discovered  by 
Pasteur.  All  these  compounds  have  the  same  internal  grouping  of  the  atoms,  although 
they  are  isomerides ;  it  is  not  possible  to  distinguish  between  them  by  chemical  reactions, 
but  they  may  be  clearly  differentiated  by  their  physical  behaviour  :  they  form  Jiemihedral, 
i.  e.,  symmetrical,  but  non-superposable  crystals  (related  as  an  object  to  its  image  in  a 


FIG.  22. 


mirror)  :  they  have,  too,  different  actions  on  polarised  light,  the  plane  of  which  is  turned 
to  the  right  by  some  and  to  the  left  by  others.  These  acids  are  hence  known  as  physical 
or  optical  isomerides. 

Pasteur  attempted  to  explain  this  isomerism  by  supposing  the  atomic  groups  to  be 
arranged  unsymmetrically  in  the  molecule,  in  some  cases  in  a  dextro-rotatory  spiral  and 
in  others  in  a  Isevo-rotatory  spiral,  or  arranged  at  the  vertices  of  an  irregular  tetrahedron. 

When  other  similar  isomerides — the  lactic  acids — had  been  discovered,  J.  Wislicenus, 
in  1873,  suggested  that  isomerism  of  this  kind  could  be  explained  only  by  regarding  the 
groups  or  atoms  of  these  compounds  as  arranged  in  space  so  as  to  form  distinct  configurations. 

This  isomerism  in  space  (stereoisomerism)  was  explained  by  van  't  Hoff  and  Le  Bel 
(1874),  independently,  by  means  of  the  hypothesis  of  the  asymmetric  carbon  atom.  The 
starting-point  of  this  hypothesis  was  Kekule's  idea  (1867)  of  regarding,  for  the  sake  of 
convenience,  the  carbon  atom  .as  situated  at  the  centre  of  a  regular  tetrahedron,  and  its 
four  affinities  as  directed  towards  the  four  vertices,  i.  e.,  arranged  homogeneously  in  space 
(Figs.  22,  23).  If  these  affinities  are  satisfied  at  the  vertices  by  monovalent  atoms  or 
atomic  groups,  the  following  cases  present  themselves :  no  isomerism  is  possible  in  the 
compounds  Ca3  b,  Ca2  62,  Ca2  be,  and  Ca  b2  c,  where  a,  b,  and  c  indicate  either  atoms  other 
than  carbon  or  groups  of  atoms  (I,  H,  OH,  etc. ) ;  the  compound  CH2I2  exists  in  only  one 
form,  and  if  we  put  the  four  atoms  (H2  and  I2)  at  the  apices  of  the  carbon  tetrahedron,  no 
matter  how  their  positions  may  be  changed,  it  is  not  possible  to  find  two  different,  i.  e., 
non-superposable,  arrangements.  If,  however,  the  four  groups  or  atoms  combined  with 
the  carbon  atom  are  all  different,  e.  g.,  Cabcd,  two  isomerides  are  possible,  and  in  this  case 
the  carbon  atom  is  termed  asymmetric  ;  in  fact,  if  these  atoms  or  groups  are  arranged, 
in  one  case,  so  that  the  circle  a,  b,  c  has  a  sense  opposite  to  that  in  which  the  hands  of  a 
clock  move  (Fig.  24,  I)  (called,  therefore,  dextro-rotatory  isomerides,  and  indicated  by  d- 
or  by  the  sign  -J- )  and,  in  the  other,  in  the  opposite  sense  (Fig.  25,  II)  (termed  Icevo-rotatory 


20 


ORGANIC    CHEMISTRY 


isomerides,  like  levulose,  and  indicated  by  I-  or  — ),  two  non-congruent  configurations  are 
obtained;  these  cannot  be  superposed,  one  on  the  other,  in  such  a  way  that  the  same 
groups  occupy  the  same  positions  in  the  two  cases.  These  two  figures  represent  two  different 
isomerides  and  are  related  in  the  same  way  as  an  object  to  its  mirror-image  or  as  the  left 
hand  to  the  .right.  Such  isomerism  is  called  enantiomorphism. 

These  two  different  arrangements  of  the  atoms  round  the  asymmetric  carbon  atom 
also  explain  how  it  is  that,  when  polarised  light  traverses  these  molecules,  its  plane  of 
polarisation  is  rotated,  in  one  case  to  the  right  and  in  the  other  to  the  left.  Van  't  Hoff 
and  Le  Bel  pushed  their  deductions  still  further,  and  showed  that  the  dextro-optical 
deviation  should  be  numerically  equal  to  the  leevo-optical  deviation  of  the  corresponding 
isomeride.  This  has  been  confirmed  practically,  and  it  also  follows  that  when  a  pair  of 


FIG.  27. 


FIG.  28. 


such  isomerides  are  mixed  in  equal  proportions,  there  should  result  an  optically  neutral 
mixture,  thus  giving  rise  to  a  special  inactive  or  racemic  isomeride.  A  substance  with 
only  one  asymmetric  carbon  atom  always  gives  three  stereoisomerides  (for  example,  three 
lactic  acids). 

It  has  also  been  deduced  theoretically  and  proved  practically  that  all  optically  active 
compounds  contain  at  least  one  asymmetric  carbon  atom,*  although  not  all  compounds  con- 
taining asymmetric  carbon  atoms  are  optically  active,  since  the  molecules  may  contain 
groups  which  neutralise  each  other's  activity. 

Many  examples  illustrating  these  principles  will  be  discussed  later  in  the  special  part 
of  this  book ;  meanwhile  mention  may  be  made  of  the  most  important  of  these  compounds  : 
leucine,  asparagine,  coniine,  the  lactic  acids  (hydro xypropionic  acids),  etc.,  which  contain 
one  asymmetric  carbon  atom  and  give,  in  each  case,  three  stereoisomerides. 


FIG.  30. 

These  cases  of  stereoisomerism,  and  those  which  follow,  will  be  understood  more  easily 
if  studied  by  means  of  cardboard  tetrahedra  with  differently  coloured  vertices. 

When  the  substance  contains  two  asymmetric  carbon  atoms,  the  number  of  stereo- 
isomerides increases  as  follows : 

If  we  take  two  tetrahedra  like  that  shown  in  Fig.  26, 1,  or  Fig.  28,  II,  representing  two 
similar  molecules  which  contain  only  one  asymmetric  carbon  atom  and  in  which  the  groups 
a,  b,  and  c,  satisfying  three  of  the  valencies,  are  arranged  in  a  dextro-rotatory  sense,  and 

1  Or  else  an  asymmetric  atom  of  nitrogen  (see  later)  or  sulphur,  tin,  etc.  The  exceptions  to 
this  rule  are  very  rare  and  uncertain,  one  of  the  cases  most  discussed  during  recent  times  (1909- 
1910)  being  l-methylcydohexylidene-l-acetic  acid,  which  does  not  appear  to  contain  an  asymmetric 
carbon  atom,  but  is  optically  active. 


A  L  L  O  I  S  O  M  E  R  I  S  M 


21 


superpose  one  tetrahedron  on  the  other,  so  that  the  free  valencies  satisfy  one  another, 
there  results  a  new  isomeride,  i.  e.,  a  molecule  with  two  dextro-rotatory  asymmetric  carbon 
atoms,  as  shown  in  Figs.  27  and  29.  * 

If  we  joiri  two  Isevo-rotatory  carbon  atoms  (Fig.  28,  II),  that  is,  the  mirror  image  of 
Fig.  26,  I,  a  Isevo-rotatory  isomeride  (Fig.  30,  II)  is  obtained. 

Finally,  if  one  dextro-rotatory  (Fig.  26,  I)  and  one  laevo-rotatory  asymmetric  carbon 
atom  (Fig.  28,  II)  are  united,  a  third  stereoisomeride  is  obtained,  which  is  permanently 
optically  inactive  (Fig.  31,  III),  the  effect  produced  on  polarised  light  by  one  asymmetric 
carbon  atom  being  destroyed  by  the  effect  of  the  other. 

In  order  to  understand  these  stereochemical  speculations  better,  we  may  apply  them 
to  the  isomerism  of  tartaric  acid,  which  has  the  formula  C4H6O6,  and  contains  two  asym- 
metric carbon  atoms  (marked  with  _ 

asterisks)  to  which  are  joined  the 
groups  OH,  CO2H,  and  H  : 

CO2H 
F 


CCLH 


FIG.  33. 


If,  for  the  letters  a,  b,  and  c  of  the  tetrahedra  considered  above,  we  substitute  the 
groups  OH,  CO2H,  and  H,  and  if  the  tetrahedron  of  Fig.  26,  1  (which  we  shall  call  +  A  ) 


be  represented  as  if  projected  on  to  a  plane,  thus  : 


a — C — c  or  OH — O— H  (dextro- 

\  I  VI 

b  CO,H 


rotatory),  and  that  of  Fig.  28,  II  (  —  A),  thus:    c—C  —  a  or  H  —  C  —  OH  (tevo-rotatory), 

I/  \        S 

b  C02H 

we  arrive  at  the  following  stereoisomerides  of  tartaric  acid  : 

I.  By  joining  two  +  A  atoms,  we  get  d-tartaric  acid  (Fig.  29  or  32,  I). 

II.  By  joining  two  —  A  atoms,  we  get  Z-tartaric  acid  (Fig.  30  or  32,  II). 

III.  By  joining  one  +  -4  atom  with  one  —  A  atom,  we  have  the  permanently  inactive 
mesotartaric  acid  (t-tartaric  acid),  as  may  be  seen  in  Fig.  31,  III,  or  32,  III. 

IV.  By  mixing,  mechanically,  equal  parts  of  acids  I  (  +  )  and  II  (  —  ),  there  results 
racemic  acid,  apparently  inactive,  but  from  which,  by  mechanical  means  (by  hand  with 
the  aid  of  a  lens),  the  two  forms  of  crystals  may  be  separated. 

It  is  often  assumed  that  the  two  asymmetric  carbon  atoms  can  rotate  independently 
on  the  common  axis  joining  them,  so  that  if  the  groups  of  one  asymmetric  carbon  atom 
exert  an  attraction  or  influence  on  those  of  the  other,  a  most  favourable  position  could 
be  attained,  a  chemical  reaction  being  sometimes  possible  between  one  group  and  another 
with  separation  of,  say,  water  and  loss  of  the  freedom  of  rotation  ;  to  the  new  isomerism 
thus  created  we  shall  refer  shortly. 

STEREOISOMERISM  IN  DERIVATIVES  WITH  DOUBLY  LINKED  CARBON 
(ALLOISOMERISM).  By  means  of  the  tetrahedra,  we  can  show  a  double  linking  between 
two  carbon  atoms  by  arranging  one  side  of  one  tetrahedron  (carbon  atom)  in  contact 
with  a  side  of  the  other  (Fig.  33). 

With  such  an  arrangement,  even  without  asymmetric  carbon  atoms,  isomerism  is 


possible.      In  fact,  a  compound  i^>C  =  G<^,   forms  the  following  isomerides  :    (1)  that 
shown  in  Fig.  34,  where  the  two  similar  atoms  or  groups  of  atoms,  e.  g.,  a  and  a,  although 

1  Looking  at  the  order  in  which  the  letters  a,  b,  and  c  come  in  the  two  asymmetric  carbon 
atoms,  it  would  seem  that  these  are  not  dextro-rotatory,  but  this  is  because  the  upper  carbon 
atom  has  been  turned  through  180°  from  its  position  in  Fig.  26;  if  its  base  is  brought  down, 
its  identity  with  the  other  dextro-rotatory  atom  becomes  evident. 


22 


ORGANIC    CHEMISTRY 


a—C—b 
united  to  two  different  carbon  atoms,  occupy  adjacent  positions  :         ||       ,  or  cts-positions 

a— C—  b 

(cis-isomerism);   such  a  molecule  exhibits  plane-symmetry,  the  two  pairs  of  similar  groups 
lying  to  the  left  and  right,  respectively,  of  the  perpendicular  plane  containing  the  common 

side   (double  linking);   (2)  that  shown  in  Fig.   35, 
a  K~        '     3 "      where  two   similar   groups  occupy   non-adjacent    or 

diagonally  opposite  or  irons- positions          ||       ,    this 

form  exhibiting  centro-symmetry. 
yJG    34  Yia    35  Similarly,  a  compound  of  the  type  a>C  =  C<Cfc 

a—C—b  a—C—b 

forms  two  isomerides,  the  cis-form,        ||        ,  and  the  trans-iorm,         || 

a — C — c  c — C — a 

The  best  illustration  of  isomerism  of  this  type  is  afforded  by  the  two  isomerides  :  maleic 
acid  (cis-form,  Fig.  36)  and  fumaric  acid  (trans-iorm,  Fig.  37). 

From  these  figures  it  is  seen  that  the  cis-iorm,  maleic  acid,  should  lend  itself  to  the 
ready  formation  of  anhydrides  (condensation  of  two  molecules  or  acid  groups  with  separa- 
tion of  one  molecule  of  water),  since  the  two  acid  groups,  C02H,  are  very  near  to 
one  another,  and  it  is,  indeed,  found  that  maleic  acid  easily  gives  an  anhydride  with 
separation  of  one  molecule  of  water  (Fig.  38),  whilst  no  anhydride  of  fumaric  acid  is 
known. 

Isomerism  of  this  kind  is  exhibited  by  various  substances,  e.  g.,  crotonic  and  isocrotonic 
acids  (CH3  •  CH  :  CH  •  COOH);  mesaconic  and  citraconic acids  [CR3  -C(COOH)  :CH  -COOH], 
etc. 

Baeyer  found  that  cases  of  isomerism  similar  to  those  just  described  occur  also  with 
cyclic  compounds  (see  Part  III),  i.  e.,  closed-chain  compounds  with  simple  Unkings  between 

•jeo 


HCCO,H 
HC.COjH 


voj: 


HOtC.CH 
HC.COj.lt 


FIG.  36. 


FIG.  37. 


FIG.  38. 


the  carbon  atoms.  He  distinguishes  with  the  sign  T  compounds  containing  true  asym- 
metric carbon  (absolute  asymmetry),  adding  the  sign  +  or  —  if  the  compound  is  optically 
active;  while  he  gives  the  name  relative  asymmetry  to  that  shown  by  compounds  with 
doubly  linked  carbon  atoms  (alloisomerism)  or  by  cyclic  compounds  with  simple  linkings, 
the  term  cis  or  trans  being  added  to  the  T.  Thus,  to  the  name  tartaric  acid  would  be 
added  the  sign  7'  +  or  T  — ,  according  as  the  acid  is  dextro-  or  laevo-rotatory,  and  to  the 
name  maleic  acid  jTCIS,  to  fumaric  acid  Zltr  ns,  etc. 

STEREOISOMERISM  OF  NITROGEN.  Le  Bel  attempted  to  explain  the  isomerism 
of  certain  nitrogen  compounds  (e.  g.,  methyl-ethyl-propyl-isobutyl-ammonium  chloride) 
by  assuming  absolute  asymmetry  for  X;he  nitrogen  atom.  A  more  plausible  explanation 
seems,  however,  to  be  afforded  by  the  idea  of  relative  asymmetry  of  the  nitrogen,  analogous 
to  that  of  carbon  atoms  when  united  by  double  linking ;  in  this  way  V.  Meyer,  Hantzsch, 
Werner,  and  others  easily  explained  the  isomerism  of  the  oximes,  hydroxamic  acids, 

Cab 
phenylhydrazones,  etc.     In  general,  a  substance  of  the  constitution  ||         should  give  two 

Nc 

isomerides,  which  may  be  represented  as  shown  in  Fig.  39  :  the  syn-series  (Fig.  39, 1)  and 
the  cmto'-series  (Fig.  39,  II). 


23 

These  investigators  also  studied  those  cases  of  isomerism  in  which  the  nitrogen  behaves 
as  a  pentavalent  element. 

Of  interest  are  the  complex  cases  of  stereoisomerism  exhibited  by  the  organic  cobalt 
derivatives  studied  by  Werner  (1911-1914)  (see  Vol.  I.,  p.  848). 

SEPARATION  AND  TRANSFORMATION  OF  STEREOISOMERIDES.  Stereo- 
isomerides  and,  in  general,  compounds  containing  asymmetric  carbon  atoms,  when  pre- 
pared artificially  in  the  laboratory  from  inactive  substances,  are  inactive,  the  racemic 
configuration,  composed  of  a  mixture  of  the  optical  antipodes  in  equal  quantities,  being 
formed.  When,  however,  these  substances  are  elaborated  in  the  animal  or  vegetable 
organism,  they  are  usually  optically  active. 

The  transformation  of  one  of  these  optical  antipodes  into  the  other  corresponding  with 
it  may  sometimes  be  effected  by  passing  through  halogen  derivatives,  separation  of  the 
halogen  from  which  results  in  the  formation  of  the  isomeride  of  opposite  optical  activity. 

•  The  separation  of  the  antipodes,  or  of  one  of  them,  from  the  racemic  isomeride  was 
carried  out  by  Pasteur  (1848)  in  various  ways.  The  following  are  the  methods  used  at 
the  present  time : 

(1)  By  fractional  crystallisation  (see  above)  of  the  racemic  isomerides  or  of  some  of 
their  salts  at  various  temperatures  and  from  various  solvents,  the  antipodes  may  be  sepa- 
rated directly  or  else  they  crystallise  in  hemihedral  forms  which  may  be  readily  separated. 
For  some  substances  it  is  convenient  to  prepare 

compounds    with  alkaloids    (optically    active 

basic  compounds,  e.  g.,  strychnine,  cinchonine, 

etc.),   which,  even  when  they  do   not  form     (ij         /    \  (II) 

well-defined  hemihedral  crystals,  may  be  easily 

separated  by  fractional  crystallisation. 

(2)  By  means  of  enzyme  action  (maltase, 
emulsin,  etc.;    see  section  on   Fermentation) 

Fischer  succeeded  in  resolving  certain  racemic        a— C b  a — C— b 

glucosides.      Much  earlier  than  this,  Pasteur  || 

discovered    that   certain    bacteria   or  moulds        c — N 
(Penicillium    glaucum,   etc.)    are    capable   of  FIG.  39. 

developing  in  a  solution  of  the  racemic  sub- 
stance at  the  expense  of  one  of  the  optical  antipodes,  the  other  being  left  unchanged. 
This  phenomenon  is  explained  by  the  fact  that  bacteria  owe  their  activity  to  certain 
substances  which  they  produce  (enzymes),  and  which  are  optically  active  and  behave 
analogously  to  optically  active  solvents.  Indeed,  in  many  cases,  stereoisomeric  antipodes 
are  separated  by  virtue  of  their  different  solubilities  in  an  optically  active  solvent. 

(3)  With  certain  racemic  compounds,  the  antipodes  are  separated  by  taking  advantage 
of  their  different  velocities  of  esterification  in  presence  of  an  optically  active  alcohol;  e.  g., 
for  racemic  mandelic  acid,  menthol  (which  is  an  active  alcohol)  is  used.     For  inactive 
alcohols  the  velocity  of  esterification  is  the  same  for  the  two  antipodes  composing  the 
racemic  compound. 

(4)  When  an  optically  active  substance  is  heated  within  certain  definite  limits  of 
temperature  (transformation  point,  see  Vol.  I.,  p.  208),  it  is  often  converted,  to  the  extent 
of  one-half,  into  the  opposite!}'  active  isomeride,  so  that  an  inactive  mixture  (racemic 
compound)  is  obtained ;  this  takes  place  readily,  for  example,  with  the  lactic  acids.     Above 
the  transformation  point  the  racemic  substance  may  form  inseparable  mixed  crystals  (see, 
Vol.  I.,  p.  116),  the  substance  being  then  called  pseudo-ratemic.     On  the  other  hand,  it 
has  been  shown  that,  with  certain  halogenated  compounds,  the  transformation  occurs 
even   at    ordinary  temperatures,  but   with  a  minimum  velocity;    thus,  with  isobutyl 
bromopropionate,  about  three  years  is  required. 

(5)  R.  Stoermer  (1909  and  1911)  found  that  the  more  stable  form  with  the  higher 
melting-point  is  often  converted  into  the  more  labile  form  by  means  of  the  ultra-violet 
rays  (mercury  vapour  lamp,  see  Vol.  I.,  pp.  238,  687),  this  occurring  especially  with  ethylene 
compounds  (crotonic  acid  forms  an  exception) ;  in  this  way  it  is  shown  that  cumarinic  acid 
is  the  cj's-alloisomeride  of  o-cumaric   acid.     The  light  acts  as  a  source  of  energy  and 
the  ns-alloisomerides  are  the  forms  containing  the  most  energy.     In  many  cases  these 
alloisomerides  cannot  be  obtained  by  other  methods;   when  left,  they  undergo  gradual 
transformation  into  the  more  stable  isomerides. 


24  ORGANIC    CHEMISTRY 


HOMOLOGY   AND   ISOLOGY 

Turning  to  the  more  simple  compounds,  those  formed  from  only  carbon 
and  hydrogen,  we  may  easily  see  what  procedure  is  necessary  to  arrive  at 
those  containing  longer  and  more  complex  chains  of  carbon  atoms.  If  we 
start  from  the  most  simple  compound,  methane  (or  marsh  gas),  CH4,  we  may 
replace  an  atom  of  hydrogen  in  it  by  other  elements  or  even  condense  two 
of  the  monovalent  CH3  residues  into  one  compound,  CH3  *  CH3,  thus  obtaining 
ethane  (C2H6).  Further,  in  this  compound  we  may  also  replace  an  atom  of 
hydrogen  by  another  — CH3  residue,  forming  propane,  CH3 — CH2 — CH3  or  C3H8, 
and  by  continuing  this  process  we  arrive  at  butane,  CH3 — CH2 — CH2 — CH3, 
i.  e.,  C4H10;  pentane,  C5H12;  hexane,  C6H14,  etc. 

All  the  compounds  of  this  series  have  analogous  structures  and  have  also 
many  analogous  chemical  and  physical  properties ;  such  a  series  is  called  a 
homologous  series. 

This  series  of  the  derivatives  of  methane  may  be  represented  by  the  general 
formula  CnH2n  +  2,  each  term  being  the  higher  or  lower  homologue  of  the 
preceding  or  following  term,  and  differing  from  it  by  having  one  CH2  complex 
more  or  less.  If  in  all  the  simple  compounds  of  this  homologous  series  of 
methane  we  replace  successively  one  hydrogen  atom  of  the  CH3  group  by  the 
hydroxyl  residue  OH  (characteristic  of  the  alcohols),  we  obtain  a  homologous 
series  of  alcohols  :  CH3OH,  methyl  alcohol;  C2H5OH,  ethyl  alcohol,  etc.,  and 
similar  series  may  be  obtained  of  aldehydes,  acids,  chloro-derivatives,  etc. 

The  homologous  compounds  of  each  of  these  series  differ  always  by  CH2 
or  by  a  multiple  of  it. 

There  are  also  other  series  with  chains  containing  double  linkings,  (i.  e., 
compounds  not  completely  saturated),  and  these  unsaturated  series  are  termed 
isologous  with  respect  to  the  first,  and,  for  an  equal  number  of  carbon  atoms, 
they  contain  less  hydrogen  (CrtH2n  or  even  CnH2,(_  2). 

Thus,  ethane  is  isologous  to  the  two-carbon-atom  compounds  of  the 
unsaturated  series,  CH2  =  CH2  (ethylene)  and  CH  =  CH  (acetylene),  etc. 

Homology  is  determined  by  the  tetra valency  of  carbon,  and  in  consequence 
the  total  number  of  hydrogen  atoms  in  these  compounds  (hydrocarbons)  is 
always  even,  i.  e.,'  divisible  by  two,  and,  if  any  of  the  hydrogen  atoms  are 
replaced  by  other  elements,  the  sum  of  the  atoms  with  odd  valencies  (Cl,  P, 
N,  As)  and  of  the  remaining  hydrogen  atoms  should  always  give  an  even 
number. 


In  many  cases,  certain  physical  properties  are  either  common  -to  whole 
groups  of  homologous  or  isomeric  substances,  or  else  vary  gradually  with 
change  of  chemical  composition.  Thus  the  physical  properties  often  contribute 
to  the  establishment  of  the  true  chemical  constitutions  of  organic  substances. 

CRYSTALLINE  FORM.  The  crystalline  form  of  an  organic  compound  is  of  con- 
siderable importance,  since  it  often  serves  to  distinguish  clearly  and  accurately  between 
two  compounds.  Two  isomeric  substances  have  often  different  crystalline  forms. 

There  are,  however,  numerous  cases  of  dimorphism  or  polymorphism  (see  Vol.  I.),  one 
of  the  forms  always  being  more  stable  than  the  others. 

We  have  already  considered  the  relations  existing  between  the  crystalline  form  and 
chemical  constitution  in  those  stereoisomerides  differing  only  by  the  enantiomorphism 
of  their  crystals. 

P.  Groth  has  discovered  also  the  law  of  morphotropy,  according  to  which  a  regular 


PHYSICAL     PROP  E-R  TIES  25 

change  is  produced  in  the  crystalline  form  of  compounds  by  gradual  substitution  with 
new  atoms  or  groups. 

The  relations  between  the  crystalline  forms  and  the  chemical  constitutions  of 
substances  have  as  yet,  however,  been  little  studied. 

SOLUBILITY.  The  hydrocarbons  and  their  substitution  derivatives  are  but  slightly 
or  not  at  all  soluble  in  water,  but  are  almost  all  soluble  in  ether  and  in  alcohol.  Of  the 
alcohols,  the  acids,  and  the  aldehydes,  the  first  terms  of  every  homologous  series  are 
soluble  in  water,  the  solubility  gradually  decreasing  as  the  number  of  carbon  atoms  in 
the  molecule  increases;  these  compounds  are,  however,  relatively  readily  soluble  in 
alcohol  or  ether.  The  polyhydric  alcohols  (glycerol,  mannitol,  etc.),  are,  however,  soluble 
in  water,  but  not  in  ether. 

The  compounds  of  the  aromatic  series  are,  in  general,  rather  less  soluble  in  alcohol 
and  in  water  than  the  corresponding  compounds  of  the  fatty  series. 

In  contact  with  two  solvents  which  do  not  mix  (see  Vol.  I.,  p.  93),  a  substance  dissolves 
in  them  both  in  a  constant  ratio,  independent  of  the  relative  volumes  of  the  two  solvents, 
but  depending  on  the  concentration  and  on  the  temperature;  thus,  in  separating  by 
means  of  ether  a  compound  dissolved  in  water,  a  better  and  more  rapid  result  is  obtained 
by  shaking  many  times  with  a  little  ether  each  time  than  by  using  fewer,  but  larger, 
quantities  of  ether. 

Of  two  isomerides,  that  with  the  lower  melting-point  is  the  more  soluble. 

SPECIFIC  GRAVITY.  Isomeric  compounds  have  different  specific  gravities,  but 
with  the  normal  hydrocarbons  (CBH2n+2)  the  values  approach  one  another  as  the  number 
of  carbon  atoms  increases :  at  about  C16H34  and  for  higher  terms  the  specific  gravity 
becomes  about  0-78.  The  specific  gravity  of  the  monobasic  fatty  acids  is  greater  than 
1  for  the  first  terms  of  the  series,  but  it  diminishes  with  augmentation  of  the  number  of 
carbon  atoms  in  the  molecule. 

MOLECULAR  VOLUME.  It  was  thought  for  many  years  that  certain  important 
rules  could  be  deduced  from  the  molecular  volumes  of  organic  compounds,  that  is,  from 
the  quotients,  M/P,  obtained  by  dividing  the  molecular  weights  (M )  by  the  specific 
gravities  (P). 

In  1842  Kopp  had  found  that,  for  liquids  at  the  boiling-point,  the  molecular  volume 
is  very  approximately  equal  to  the  sum  of  the  atomic  volumes  of  the  component  elements. 
For  homologous  compounds,  the  molecular  volume  increases  by  about  22  for  every  added 
CH2  group.  More  recent  studies  (Lossen,  R.  Schiflf,  Horstmann,  Traube,  etc.)  show, 
however,  that  these  regularities  are  only  relative  and  that  isomeric  compounds  do  not 
possess  equal  molecular  volumes.  In  unsaturated  series  every  double  linking  increases  the 
molecular  volume  and,  with  closed-chain  compounds,  the  molecular  volume  is  less  than 
those  of  the  corresponding  open-chain  compounds  with  double  linkings.  Thus,  in  general, 
the  molecular  volume  depends  not  only  on  additive  factors  (e.  g.,  the  sum  of  the  atomic 
volumes),  but  also  on  constitutive  factors  (different  linkings  between  the  carbon  atoms). 

MELTING-POINT.  Of  two  isomerides,  that  with  the  more  symmetrical  structure 
has  the  higher  melting-point.  The  members  of  a  series  have  varying  melting-points, 
those  with  odd  numbers  of  carbon  atoms  having  lower  melting-points  than  those  imme- 
diately below  them  with  even  numbers.  There  are,  in  addition,  other  less  important 
rules,  but  all  present  exceptions.  A  mixture  of  two  substances,  in  suitable  proportions, 
often  has  a  melting-point  lower  than  that  of  either  of  the  components. 

BOILING-POINT.  In  compounds  of  the  same  series,  the  boiling-point  rises  with 
increase  of  molecular  weight,  the  amount  of  the  increase  being  about  20°  per  CH2  in  the 
methyl  alcohol  or  formic  acid  series,  and  about  30°  for  benzene  derivatives  with  methyl 
groups  in  the  nucleus.  The  boiling-points  of  isologous  hydrocarbons,  that  is,  those  of 
the  same  number  of  carbon  atoms  but  of  different  series  (derivatives  of  methane,  ethylene, 
and  acetylene),  are  very  close  to  one  another. 

Of  the  isomeric  compounds  of  the  aliphatic  series,  the  normal  one  boils  at  the  highest 
temperature  and  the  boiling-point  is  increasingly  lowered  by  increase  in  the  branchings. 

The  substitution  of  hydrogen  by  halogens  and  by  hydroxyl  groups  raises  the  boiling- 
point.     The  ethers  boil  at  lower  temperatures  than  the  corresponding  isomeric  alcohols. 
HEAT  OF  COMBUSTION  AND  HEAT  OF  FORMATION  FROM  THE  ELEMENTS 
(see  Vol.  I.,  pp.  60,  111,  460).     The  Hess-Berthelot  law  states  that  the  difference  between  the 
heats  of  combustion  of  two  equivalent  chemical  systems  is  equal  to  the  heat  developed  in  the. 


26 


ORGANIC    CHEMISTRY 


transformation  of  one  system  into  the  other,  that  is,  is  equal  to  the  heat  of  formation  of  the  latter 
from  the  elements.  In  general,  then,  we  can  calculate  the  heat  of  formation  from  its  elements 
of  an  organic  compound  by  subtracting  its  heat  of  combustion  from  the  sum  of  the  heats 
of  combustion  of  the  elements  composing  it.  As  an  example  :  the  heat  of  combustion 
of  methane,  CH4,  at  constant  volume  is  211,900  cals. ;  the  heat  of  combustion  of  carbon 
(C  +  O2  =  C02)  being  97,000  cals.  and  that  of  hydrogen  (H2  +  O  =  H2O)  68,400  cals., 
the  complete  combustion  of  methane  is  given  by  the  following  equation  :  CH4  -j-  2O2  = 
CO2  +  2H2O  =  97,000  +  (2  X  68,400)  =  233,800  cals.,  the  sum  of  the  heats  of  com- 
bustion -of  the  component  elements  of  methane.  The  heat  of  formation  of  methane,  will 
then  be  given  by:  233,800—211,900=21,900  cals.,  which  also  represents  the  heat 
necessary  to  resolve  methane  into  its  elements  in  order  to  initiate  its  combustion.  The 
heat  of 'combustion  of  ethyl  alcohol  being  340,000  cals.,  that  of  acetic  acid  210,000,  and 
that  of  ethyl  acetate  554,000,  the  heat  of  formation  of  the  last-named  from  the  first  two 
will  be  :  340,000  +  210,000  —  554,000  =  —  4000  cals. 

In  the  analogous  paraffin  and  olefine  series,  a  difference  of  CH2  corresponds  with  a 
variation  of  150,000  to  160,000  cals.  in  the  molecular  heat  of  combustion. 

The  heats  of  combustion  of  isomeric  compounds  are  equal,  if  the  compounds  are  chemi- 
cally similar,  for  example,  methyl  acetate  (CH3  •  CO2CH3)  and  ethyl  formate  (H  •  COZC2H5), 
but  different  if  the  compounds  are  of  different  molecular  character  (for  example,  allyl 
alcohol,  CH2:  CH  •  CH2  •  OH,  .and  acetone,  CH3  •  CO  •  CH3),  compounds  with  multiple 
linking  in  the  fatty  series  having  higher  heats  of  combustion  than  the  corresponding  cyclic 
isomerides. 

These  calculations  are  also  of  importance  for  the  evaluation  of  the  energy  produced  in 
organisms  by  the  transformations  of  various  foods  (see  also  later  in  the  section  on 
Explosives).1 

HEAT  OF  NEUTRALISATION.  With  the  organic  acids  this  is  the  same  for  all, 
namely,  13,700  cals.  (see  Vol.  I.,  p.  99),  as  long  as  the  resulting  salts  are  not  decomposed 
by  water;  with  tne  phenols  (cyclic  compounds  containing  OH)  the  heat  of  neutralisation 
is  about  one-half  the  above  value,  or  more  if  the  acid  character  is  intensified  by  the  presence 
of  the  NO2  group;  with  the  alcohols  it  is  almost  zero. 

OPTICAL  PROPERTIES.  (1)  Colour.  Most  organic  compounds  are  colourless,  but 
if  they  contain  iodine  or  the  nitro-group  or  doubly  linked  nitrogen  atoms  (— -N  =  N — ), 
or  two  oxygen  atoms  directly  united,  they  are  generally  coloured,  especially  in  the  aromatic 
series. 

\ 

1  The  following  are  the  heats  of  formation  from  the  elements  of  certain  organic  compounds, 
expressed  in  large  calories  per  gram-molecule  : 


Cals. 

Naphthalene,  C10H8 :  solid        .          .  —  42 
Nitronaphthalene,  C10H7N02  :  solid        -   14-7 
Dinitronaphthalene,        C10H6(NO2)2  : 

solid -       5-7 

Trinitronaphthalene,      C10H5(N02)3 

solid  .....  -       3-3 

Acetylene,  C2H2 :  gas       .          .  —   61-4 

Ethylene,  C2H4 :  gas        .          .  -  -   15-4 

Benzene,  C6H6 :  gas         .          .  -  -   10-2 
Nitrobenzene,  C6H6N02  :  liquid  4-2 

Dinitrobenzene,  C6H4(N02)2 :  solid  12-7 

Mannitol,  C6H1406 :  solid          .  .  320 
Nitromannitol,  C6H8N6018  :  solid      .         179-1 
Mercury       fulminate,        C2N202Hg 

solid -   62-9 

Anthracene,  C14H10 :  solid        .  --  42-4 

The  heats  of  combustion  of  various  organic  compounds  are  as  follow  :  ethyl  alcohol,  340  Cals. ; 
methyl  alcohol,  182-2;  mannitol,  727;  cellulose,  680;  terephthalic  acid,  771 ;  diphenyl,  1494; 
cane  sugar,  1355 ;  acetic  acid,  210;  benzole  acid,  772 ;  ethyl  acetate,  554 ;  urea,  152;  benzene, 
779-8;  dihydrobenzene,  848;  tetrahydrobenzene,  892;  toluene,  933;  hexane,  991-2;  methane, 
211-9;  ethane,  370-4;  propane,  529-2;  trimethylmethane,  687-2;  ethylene,  333-4;  propylene, 
492-7;  trimethylene,  499-4;  isobutylene,  650-6;  methyl  chloride,  164-7;  ethyl  chloride,  321-9; 
propyl  chloride,  480-2;  chloroform,  70-5;  dinitrobenzene  (o-,  m-,  and  p-),  about  700;  trinitro- 
benzene,  666  to  681;  succinic  acid,  357;  azelaic  acid,  1141;  erucic  acid,  3297;  tribrassidinic 
acid,  10,236;  glucose,  674;  oxalic  acid,  60-2;  formic  acid,  62-8;  hydrocyanic  acid,  152-3; 
naphthalene,  1233-6;  phenol,  732;  pyrogallol,  639. 


Methyl  alcohol,  CH3OH  :  liquid 
Ethyl  alcohol,  C2H5OH  :  liquid 
Phenol,  C6H5OH  :  liquid 
Trinitrophenol  (picric  acid), 

C?H2OH(N02)3  :  solid 
Sodium     picrate,     C6H2ONa(N02)3 : 

solid  ...... 

Ammonium  picrate,  solid 

Ether,  (C2H5)2o{ffqsuid   ; 

Glycerol,  C3H5(OH)3  :  liquid    . 
Trinitroglycerol,  C3H5(ON03)3 

liquid  . 

Cellulose  (cotton),  C6H1005  :  solid 
Nitrocellulose,  solid 


Gals. 
62 
70-5 
34-5 

49-1 

117-5 

80-1 
65-3 
72 
165-5 

196 

227 
624-696-706 


OPTICAL    ACTIVITY 


27 


In  the  section  on  Dyes  are  given  detailed  illustrations  of  the  remarkable  relations 
between  the  chemical  constitution  of  organic  compounds  and  their  colour. 

(2)  Refraction.  This  is  the  deviation  produced  in  the  direction  of  a  ray  of  light 
(homogeneous;  for  example,  sodium  light)  on  passing  through  a  transparent  liquid,  and 
varies  with  the  substance.  The  index  ofi  refraction  n  varies  with  the  temperature,  and 
hence  with  the  specific  gravity  (d)  of  the  substance.  The  relation  between  these  two 

nz j      i 

values  which  gives  the  refraction  constant  M  (or  specific  refractivity)  is:  -  0  ,    ^  •  -=  JR, 


which  is  almost  independent  of  the  temperature. 


2     d 

By  multiplying  by  the  molecular 
•n% j     p 

weight  P,  the  molecular  refraction  is  obtained  :  M  =  — - —  -  •  — ,  this  being  constant  for 

n   — |—  £i     a 

true  isomerides  and  changing  by  a  constant  amount  for  a  constant  change  in  the 
composition. 

The  molecular  refraction  of  a  compound  is  approximately  equal  to  the  sum  of  the 
elementary  atomic  refractions,  but  here  double  and  triple  linkings  have  an  influence,  so 
that  these  can  be  detected  in  an  organic  compound  by  means  of  the  refraction  (true  double 
linkings  of  the  aliphatic  series  are  often  distinguished  in  this  way  from  the  cyclic  linkings 
of  benzene). 

(3)  Polarised  Light.  Owing  to  the  importance  of  this  phenomenon  for  whole  groups 
of  organic  substances,  it  will  be  useful  to  recall  briefly  in  a. note  x  the  fundamental  ideas 
on  polarised  light. 

1  The  luminous  waves  of  white  light  are  propagated  in  the  cosmic  ether  with  a  velocity  of 
about  300,000  kilometres  per  second,  and  there  are  physical  instruments  which  admit  of  the 

measurement  of  the  time  required  for  a  ray  of  light 

to  traverse  a  few  metres ;  indeed,  Foucault  measured 

the  time  taken  by  light  to  pass  over  a  distance  of 

120  metres. 

By  studying  the  phenomena  of  interference  of 

light  rays,  it  can  be  shown  that  the  vibrations  of  the 

ether  in  them  are  not  longitudinal,  i.  e.,  along  the 

direction  of  propagation  of  the  ray,  but  that  the 

ether  particles  vibrate  in  all  directions  in  a  plane 
perpendicular  to  the  direction  of  the  ray  (a  transverse  section  of  a 
ray  is  shown  in  Fig.  40 ),  whilst  the  propagation  of  sound  is  effected 
by  means  of  longitudinal  vibrations  in  the  direction  of  the  path 
traversed  by  the  sound. 

A  ray  that  enters  a  liquid  or  a  non-crystalline  solid,  or  a  crystal 
of  the  regular  system  (cube  or  octahedron )  gives  only  one  refracted 
ray;  when  it  enters  a  crystal  of  the  rhombohedral  system,  two 
refracted  rays  are  formed,  one  extraordinary  and  the  other  ordinary  ; 
when  a  ray  enters  a  crystal  of  any  other  system,  two  refracted  rays 
are  formed,  but  these  rays  both  behave  like  the  extraordinary  ray, 
and,  like  the  latter,  they  do  not  obey  the  laws  of  refraction, 


FIG.  40. 


c 

FIG.  41. 


according  to  which  an  incident  ray,  perpendicular  to  a  medium  with  parallel  faces,  should  not 
be  deviated  or  refracted. 

If  a  ray  of  light,  J  i  (Fig.  41 ),  strikes  a  rhombohedral  crystal  of  Iceland  spar  perpendicularly 
to  the  face  A  B  C  D,  the  ray  divides  into  two.  The  one,  i  o  0,  continues  in  the  same  direction, 
the  other,  i  e,  is  deviated,  but  when  it  emerges  from  the  crystal  assumes  the  direction  e  E,  parallel 
to  the  original  direction.  The  two  parallel  rays  leaving  the  crystal  have  equal  luminosities, 
^_  but  o  0  follows  the  ordinary  laws  of  refraction  (vide  supra) 

(I  S  dffflHIlN  ^1^      anc^  *s  ca^ec^  the  ordinary  ray,  whilst  the  other,  e  E,  does  not 

V_y  vljjm/  S'       s"  ^^V     °bcy  these  laws  and  is  termed  the  extraordinary  ray. 

If  the  crystal  is  rotated  about  the  incident  ray  J  i  as  an 
imaginary  axis,  the  position  of  the  ray  o  0  does  not  change, 
whilst  the  ray  e  E  moves  in  the  sense  in  which  the  crystal 
is  rotated.  The  extraordinary  ray  i  e  always  lies  in  the 
plane  of  the  principal  axis  of  the  crystal  d  b  B  D,  which  passes 
through  the  principal  axis  of  the  crystal  b  0  and  is  parallel 
to  it.  These  two  rays  emerging  from  the  crystal  have, 
however,  properties  different  from  those  of  the  incident  ray  J  i  ;  in  fact,  if  either  of  the 
two  refracted  rays  (e  E  or  o  0)  is  passed  into  a  second  rhombohedron  of  Iceland  spar,  two 
new  rays  (double  refraction)  are  obtained,  but  the  intensities  of  the  two  rays  vary  according 
to  the  relative  positions  of  the  two  crystals.  Thus,  if  a  ray  emerging  from  the  first  crystal 
passes  perpendicularly  into  the  second  crystal,  the  principal  section  of  which  is  parallel  to 
that  of  the  first,  no  double  refraction  is  observed,  only  one  ray  leaving  the  second  crystal 
(s  in  Fig.  42,  the  second  hypothetical  ray  n  being  not  visible  and  marked  black  in  the 
figure).  If,  however,  the  second  crystal  is  rotated  round  the  imaginary  axis,  o  0,  a  second  ray 


FIG.  42. 


28 

Those  organic  substances  are  called  optically  active  which  rotate  the  plane  of  polarised 
light.  Some  substances  are  optically  active  in  the  crystalline  state  (not  in  the  amorphous 
state  or  in  solution),  and  hence  the  action  on  polarised  light  is  due  in  these  cases  to  the 
peculiar  arrangement  of  the  molecules;  very  few  are  active  in  both  the  crystalline  and 
amorphous  states,  the  majority  exhibiting  activity  only  in  a  dissolved  condition  (sugars, 
etc.  ),  where  the  phenomenon  depends  on  the  arrangement  of  the  atoms  or  groups  of  atoms 
in  the  molecule.  This  holds  also  for  camphor  and  oil  of  turpentine,  which  are  active  even 
in  the  form  of  vapour. 

The  longer  the  layer  (1)  and  the  greater  the  concentration  of  the  solution  (p  =  grams 
of  dissolved  substance  in  100  of  solution)  traversed  by  the  polarised  light,  the  greater 
will  be  the  rotation  of  the  plane  of  polarisation.  Referring  the  observed  rotation  a  to  a 
length  of  10  cm.  of  a  solution  containing  1  gram  of  pure  substance  in  1  c.c.  (  =  pd  /1  00, 
where  d  is  the  specific  gravity  of  the  solution),  we  get  the  specific  rotatory  power  of  the 
solution  for  the  yellow  sodium  light  (D  line  of  the  spectrum  1)  by  means  of  the  following 

formula:    [a]D  =  j-j  —  .      For    active    liquid    substances    examined    without    solvent, 


fajj,  =     v     The  molecular  rotation  (for  a  molecular  weight  M)  is  given  by  :  (M)  =         -T-*. 
I.  d 

For  a  definite  solvent  and  given  concentration  and  temperature,  every  active  substance 
(and  such  are  almost  all  those  containing  asymmetric,  carbon,  see  p.  19)  has  a  constant  and 
characteristic  specific  rotatory  power,  either  to  the  right  (+  )  or  to  the  left  (  —  ).  This 
varies  with  the  nature  and  degree  of  electrolytic  dissociation  of  the  solvent,  and  increases 
with  dilution  and  diminishes  with  rise  of  temperature;  for  purposes  of  comparison,  it  is 
usually  determined  at  20°,  and  is  then  indicated  thus  :  [a]^.  By  repeating  the  determina- 
tions and  using  moderately  high  concentrations,  the  influence  due  to  the  solvent  is  deter- 
mined and,  on  subtracting  this,  the  true  specific  rotation  is  obtained.  Freshly  prepared 
solutions  of  certain  sugars  exhibit  the  phenomenon  of  muta-rotation,  which,  however, 
disappears  after  a  time  or  on  boiling  the  liquid,  the  normal  rotation  then  being 
given. 

This  important  property  of  optically  active  compounds  is  studied  by  means  of  special 
apparatus  termed  polarimeters,  which  are  used  particularly  in  the  analysis  of  sugars  (and 
hence  often  called  saccharimeters),  and  will  be  described  in  the  section  dealing  with  this 
group  of  substances. 

MAGNETIC  ROTATORY  POWER.  All  liquids  in  a  magnetic  field  produce  a  greater 
or  less  rotation  of  the  plane  of  polarised  light,  according  to  their  chemical  composition 
and  in  conformity  with  the  laws  governing  the  refractivity  of  light.  In  many  cases  the 

(extraordinary)  suddenly  appears,  i.  e.,  double  refraction  takes  place,  and  whilst  the  luminosity 
of  the  new  ray  increases,  that  of  the  first  ray  becomes  weaker  and  when  the  principal  sections  of 
the  two  crystals  form  an  angle  of  45°,  the  two  rays  have  equal 
intensities  («',  »');  if  the  crystal  is  rotated  still  more,  the  extra- 
ordinary ray  becomes  more  luminous,  whilst  the  first  (ordinary) 
decreases  in  luminosity,  and  when  the  principal  sections  are 
perpendicular  to  one  another,  the  intensity  of  the  ordinary  ray  («'  ) 
_  is  zero  (/.  e.,  it  is  not  seen),  only  the  extraordinary  ray  being  seen 

FIG.  43.  with  its  maximum  intensity  (n").     The  light  rays  emerging  from 

the  second  rhombohedron  are  hence  different  from  those  emerging 

from  the  first,  the  latter  not  varying  in  intensity  when  the  prism  is  rotated,  whilst  the  others 
do  so. 

The  rays  leaving  the  first  prism  are  called  polarised,  and  are  distinguished  from  ordinary 
light  rays,  since,  on  passing  through  a  second  prism,  they  undergo  the  changes  described  above. 
A  polarised  ray  passes  as  an  ordinary  ray  through  a  second  rhombohedron  only  when  its  plane 
of  polarisation  is  parallel  to  the  principal  section  of  the  new  rhombohedron.  It  is  found,  then, 
that  the  plane  of  polarisation  of  the  polarised  ordinary  ray  is  perpendicular  to  the  plane  of 
polarisation  of  the  extraordinary  ray.  Hence,  the  rays  E  and  0  vibrate  in  planes  perpendicular 
to  one  another  (Fig.  43). 

POLARISATION  BY  REFLECTION.  Polarised  light  rays  are  .obtainable,  not  only  by  double 
refraction,  but  also  by  reflection  under  special  conditions,  namely,  when  a  light  ray  falls  on  a  plate 
of  glass  at  an  incident  angle  of  54°  35'. 

Polarised  light  is  also  obtained  by  simple  refraction,  by  passing  a  ray  of  light  through  a 
series  of  superposed  parallel  plates  or  through  sheets  of  tourmaline. 

1  The  angle  of  rotation  varies  with  the  length  of  the  light-wave  and  is  greater  for  violet 
rays  (which  have  a  smaller  wave-length  and  are  hence  refracted  more)  and  less  for  red  rays 
(which  have  a  greater  wave-length  and  are  hence  less  refrangible). 


NOMENCLATURE  29 

constitution  of  a  substance  has  been  determined  or  confirmed  by  measuring  the  molecular 
magneMc  rotation. 

ELECTRICAL  CONDUCTIVITY.  We  must  refer  the  reader  to  the  detailed  treat- 
ment of  electrolytic  dissociation  and  the  theory  of  ions  in  Vol.  I.  (pp.  94  et  seq,),  as  the 
same  is  directly  applicable  to  organic  compounds,  especially  as  regards  the  conductivity 
of  salts,  acids,  bases,  etc. 

CLASSIFICATION   OF   ORGANIC   SUBSTANCES 

These  are  usually  divided  into  two  large  series  : 

(1)  That  of  the  open-chain  carbon  compounds  or  methane  derivatives,  termed 
also  compounds  of  the  fatty  or  aliphatic  series,  as  all  the  fats  and  many  of  their 
derivatives   belong  here.     This   series   embraces   two   groups   of   substances : 
that  of  the  saturated  compounds  or  derivatives  of  the  paraffins  (CBH2B+2)  and 
that  of  the  unsaturated  compounds  (defines,  C,,H2n  and  derivatives  of  acetylene, 
CBH2n_2). 

(2)  That  of  the  closed-chain  carbon  derivatives,  these  being  subdivided 
into  : 

(a)  The   isocyclic  or  carbocyclic  compounds,  which  have  the  closed  chain 
formed  either  of  nuclei  of  six  carbon  atoms  with  six  available  valencies  to 
every   nucleus    (CnH2n^6,  benzene  derivatives   or   aromatic   compounds)   or   of 
nuclei  with  different  numbers  of  carbon  atoms,  but  more  highly  hydrogenated 
(cycloparaffins,  cyclo-olefines,  and  polymethylene  derivatives). 

(b)  The  heterocyclic  compounds,  the  closed  chain  of  which  contains  atoms 
(N,  P,  S,  O,  etc.)  other  than  carbon. 

The  hydrogenated  compounds  of  carbon  are  called  hydrocarbons  and  are 
termed  saturated  when  the  carbon  atoms  are  joined  by  single  valencies,  and 
the  other  valencies  are  all  satisfied  by  hydrogen.  These  saturated  hydro- 
carbons cannot  combine  with  a  further  quantity  of  hydrogen. 

Hydrocarbons  containing  carbon  atoms  united  by  double  or  triple  linkings 
are  called  unsaturated  hydrocarbons,  and  these  can  combine  with  further 
quantities  of  hydrogen,  thus  becoming  saturated.  Other  important  hydro- 
carbons are  those  with  closed  chains,  which  we  shall  study  in  Part  III  of  this 
book. 

Usually  in  homologous  series,  with  increase  in  the  number  of  carbon  atoms, 
the  compounds  pass  from  the  gaseous  to  the  liquid  and  solid  states ;  e.g., 
formic  acid,  with  one  carbon  atom,  is  a  liquid  and  boils  at  99°,  while  the 
homologous  acid  with  sixteen  carbon  atoms  is  a  solid  and  boils  at  over  300°. 

OFFICIAL   NOMENCLATURE 

With  the  continuous  development  of  organic  chemistry  and  the  multiplication  of  new 
comjxmnds,  the  need  was  often  felt  for  a  rational  method  of  naming  compounds  which 
would  facilitate  the  treatment  of  these  vast  numbers  of  compounds.  For  the  new  nomen- 
clature to  be  the  more  efficacious  it  needed  to  be  international,  because  everywhere  there 
reigned  the  greatest  confusion  in  the  naming  of  chemical  compounds,  this  referring  either 
to  the  starting  substance  or  to  the  new  group  to  which  they  belonged,  or  to  the  use  for 
which  they  were  intended,  or  to  the  molecular  constitution,  and  so  on,  so  that  the  same 
substances  often  had  four  or  five  names. 

In  1892,  at  an  International  Convention  of  Chemists  at  Geneva,  a  general  system  of 
nomenclature  of  organic  compounds  was  agreed  on.  This  is  gradually  being  introduced 
into  chemical  literature,  and,  although  not  always  felicitous,  it  has  helped  to  simplify  the 
naming  of  compounds  and  to  reduce  the  confusion. 

Following  only  in  part  the  ideas  proposed  by  Kolbe  many  years  before,  the  new  nomen- 
clature derives  the  names  of  all  compounds  from  the  names  of  the  fundamental  hydro- 
carbons to  which  the  compounds  can  be  referred,  taking  into  account  the  number  of 
carbon  atoms  present  as  well  as  the  nature  of  the  linking.  Thus,  to  the  fundamental 


80  ORGANIC    CHEMISTRY 

names  of  the  saturated  hydrocarbons  :  methane,  ethane,  propane,  butane,  pentane, 
hexane,  heptane,  etc.,  the  addition  of  the  suffix  ol  indicates  the  presence  of  the  hydro  xyl 
group  —  OH,  and  thus  an  alcohol,  for  example,  methanol  (methyl  alcohol),  ethanol  (ethyl 

/     s°\ 

alcohol),  etc.;    the  suffix  al  serves  to  denote  the  aldehyde  group  I  —  C^       I,  thus,  e.  g., 


methanal  =  formaldehyde,  eihanal  —  acetaldehyde,  etc.  ;  the  suffix  one  indicates  the 
ketonic  group  (  —  CO—  ),  thus,  propanone  (commonly  called  acetone),  etc.  The  suffix 
oic  is  used  to  indicate  the  organic  acids,  which  all  contain  the  characteristic  carboxyl  group 

*0    ^ 
—  C02H,  i.  e.,  —  C\          ),  and  thus  we  have  methanoic  (formic)  acid,  ethanoic  (acetic) 


HO 

acid,  propanoic  (propionic)  acid,  butanoic  acid,  pentanoic  acid,  etc. 

For  the  unsaturated  doubly  linked  hydrocarbons  the  fundamental  hydrocarbon 
ethylene  is  distinguished  with  the  name  of  ethene,  and  that  with  a  triple  bond  between  the 
two  carbon  atoms  (acetylene)  is  called  ethine. 

With  the  saturated  hydrocarbons,  isomerides  with  branched  chains  are  referred  to  the 
normal  hydrocarbon  (i.  e.,  non-  branched)  with  the  longest  chain  present  in  the  molecule, 
numbering  progressively  its  carbon  atoms,  starting  at  the  end  nearest  to  the  point  where 
branching  occurs.  The  name  begins  with  that  of  the  residue  of  the  side-  chain,1  then 
follow  the  successive  numbers  of  the  atoms  of  the  normal  chain  where  side-chains  join 
on,  and  finally  comes  the  name  of  the  normal  hydrocarbon. 

(1)      (2)      (3) 
CHjj—  GH  —  OH3 

CH3 

bears  the  official  name  methyl-2-propane  (some  call  it  propyl-2-methane),  and  iso  pentane, 

(1)      (2)     (3)        (4) 


CH3 

that  of  methyl-2-butane,  etc. 

When  there  are  also  secondary  ramifications  a  supplementary  numbering  is  used; 
thus,  for  isodecane, 

(1)       (2)       (3)       (4)      (5)       (6)      (7) 


(41)  CH—  CH3 

(4")  CH3 
the  official  name  would  be  metho-4I-ethyl-4-heptane. 

1  The  names  of  the  hydrocarbon  residues,  called  also  alkyl  groups,  are  formed  from  the  root 
of  the  name  of  the  corresponding  hydrocarbon,  with  the  suffix  yl  ;  thus,  with  methane  corresponds 
the  methyl  residue,  —  CH3  ;  with  ethane,  ethyl,  —  C2H5  ;  'and  then  follow  propyl,  —  C3H,  ;  butyl, 
—  C4H9,  etc. 


SATURATED     HYDROCARBONS 


PART   II.    DERIVATIVES   OF  METHANE 

AA.     HYDROCARBONS 

THE  hydrocarbons  form  a  very  large  and  important  group  of  organic  sub- 
stances, which  are  composed  only  of  hydrogen  and  carbon,  and  give  rise  to 
other  most  varied  substances  by  replacement  of  part  or  all  of  the  hydrogen 
by  other  elements  or  groups. 

For  the  reasons  given  on  p.  29,  they  are  divided  into  two  main  groups  : 
saturated  and  unsaturated  hydrocarbons. 

(a)  SATURATED   HYDROCARBONS 

These  are  called  saturated  because  the  linkings  between  the  carbon  atoms 

are  simple  ones  and  all  the  valencies  are  saturated,  so  that  hydrogen,  chlorine, 

bromine,  iodine,  ozone,  etc.,  cannot  be  added  to  them ;  the  halogens  do,  indeed, 

react  with  saturated  hydrocarbons   (fluorine  reacts  with  methane  even  at 

-  187°),  but  by  substitution  of  the  hydrogen  atoms. 

They  are  called  also  paraffins,  since,  like  the  common  solid  paraffin  waxes, 
all  the  saturated  hydrocarbons  resist,  in  the  cold,  the  action  of  chromic  acid, 
potassium  permanganate,  and  concentrated  nitric  and  sulphuric  acids,  and 
are,  in  general,  compounds  with  an  almost  indifferent  chemical  character. 
In  the  hot,  However,  energetic  oxidising  agents  convert  them,  more  or  less 
completely,  into  carbon  dioxide  and  water. 

As  a  general  rule,  these  hydrocarbons  are  insoluble  in  water  and  only 
some  of  them  dissolve  in  alcohol,  whilst  almost  all  are  soluble  in  ether. 

Of  the  direct  or  continuous  (normal)  and  branched  (isomeric)  open  chains, 
mention  has  already  been  made  on  pp.  17  and  29,  and  it  may  be  seen  how, 
starting  from  the  hydrocarbon,  C4H10,  the  number  of  isomerides  rapidly 
increases  :  2  for  butane ;  3  for  pentane,  C5H12 ;  5  for  hexane,  C6H14  (all  known) ; 
while  for  C12H26  the  number  theoretically  possible  is  355  and  for  C13H28,  892, 
only  some  of  which  are,  however,  known.  All  the  terms  of  the  paraffin  series 
can  be  represented  by  the  general  formula  CnH2n  +  2,  and  the  following  Table 
(p.  32)  gives  the  name,  formula,  boiling-point,  and  melting-point  of  the  principal 
known  paraffins.  The  official  nomenclature  is  described  on  p.  29. 

The  first  members  of  the  series  are  gases,  then  follow  liquids  as  far  as 
C15,  and  beyond  that,  solids,  the  boiling-  and  melting-points  rising  with  increase 
of  the  molecular  weight  (see  p.  25). 

NATURAL  FORMATION  AND  GENERAL  METHODS  OF  PRODUCTION. 
These  hydrocarbons,  from  the  lowest  gaseous  members  to  the  highest  solid 
ones  (paraffin  wax),  occur  abundantly  as  the  almost  exclusive  components  of 
petroleum  (especially  that  from  America),  and  it  is  not  difficult  to  separate 
single  individuals  from  these  complex  mixtures. 

In  many  natural  emanations  of  inflammable  gas,  methane  and,  to  some 
extent,  ethane  are  found  in  large  proportions,  and  the  solid  hydrocarbons 
occur  also  in  ozokerite  (which  see). 

31 


32 


ORGANIC    CHEMISTRY 


The  gaseous,  liquid,  and  solid  hydrocarbons  are  formed  abundantly  on  the 
dry  distillation  of  wood,  lignite,  bituminous  schists,  and  coal,  especially  boghead 
and  cannel coals,  which  are  relatively  rich  in  hydrogen  (see Illuminating  Gas); 

SATURATED  HYDROCARBONS,  CBH2n+2 
(After  hexane,  only  the  normal  ones  are  given) 


Melting-point. 

Boiling-poiut. 

Specific  Gravity. 

CH4       Methane        .... 

-184° 

-164° 

6-415  (-164°) 

(760mm.) 

0-555 

(0°,  760  mm.  ) 

C2H6      Ethane          .          .          . 

-172-1° 

-84-1° 

0-446  (0°) 

(749  mm.) 

(0°at23-8atm.) 

C3H8      Propane        .         .         . 

-  45° 

—  44-5° 

0-535 

(0-  at  5  atms.  ) 

(0°,  liquid) 

f  normal 
C,,Hin     Butanes  < 

[ISO 

— 

+   1° 
—  17° 

0-600  (0°) 
0-6029  (0°) 

{normal 

—  200° 

+  36-3° 

0-454  (0°) 

iso        .          .   • 

—  • 

+  30-4° 

0-622  1 

tertiary 

-  20° 

+  9° 

at 

/normal 

— 

69° 

0-6603  V       o 

dimethylisopropyl- 

methane    . 

— 

58° 

0-666  J 

dimethylpropyl- 

C6H14     Hexanes  /      methane    . 

— 

62° 

0-6766  (0°) 

methyldiethyl- 

methane    . 

— 

64° 

0-677  " 

trimethylethyl- 

methane    . 

— 

49-6° 

0-6488 

C,H1C    Heptane 



98-3° 

0-683 

at 

C8H18     Octane          .... 

— 

125-8° 

0-702 

20° 

C9H20    Nonane         .... 

-  51° 

150° 

0-718 

C10H22  Decane         .... 

-  31° 

173° 

0-7467, 

^11^24  Undecane     .... 

-  26° 

196° 

0-7581\ 

C12H26  Dodecane      .... 

-  "12° 

215° 

0-7684 

^13^28   Tridecane     .... 

-     6° 

234° 

0-775 

C14H30  Tetradecane 

+     4° 

252° 

0-775 

C15H32  Pentadecane 

+   10° 

270° 

0-776 

CjgHj^  Hexadecane 

18° 

287° 

0-775 

C17H36  Heptadecane 

22° 

303° 

0-777 

C18H38   Octodecane  .... 

28° 

317° 

0-777 

C19H40  Nonodecane 

32° 

330° 

0-777 

'o 

C20H42  Eicosane       .... 

37° 

205°  ^ 

0-778 

ft 

C21H44  Heneicosane 

40° 

215° 

0-778 

_g 

^22^46  Docosane      .... 

44° 

224° 

0-778 

15 

^gHjs   Tricosane      .... 

48° 

234° 

e 

E 

0-779 

a 

^24^50  Tetracosane 

51° 

243° 

00 

0-779 

8 

^25^52  Pentacosane 

53-5° 

— 

f-l 

— 

^ 

CggH^  Hexacosane 

58° 

— 

ft 
. 

— 

cS 

C2?H56  Heptacosane 

60° 

270° 

f  S 

0-780 

C28H58   Octocosane  .... 

60° 

— 

— 

C29H60  Nonocosane 

63° 

about  340° 

rt 

— 

CgjH^  Hentriacontane 

68° 

302° 

•«a 

0-781 

CggHgg  Dotricontane  (Dicetyl)  . 

70° 

310° 

0-781 

^35^2  Pentatricontane     . 

75° 

331° 

0-782. 

C60H122  Hexacontane 

101° 

/ 

J 

METHANE  33 

also  when  petroleum  residues  are  strongly  heated  under  pressure  (cracking), 
hydrocarbons  similar  to  petroleum  and  also  gaseous  ones  are  formed. 

Of  the  numerous  synthetical  methods  of  preparation  of  the  saturated 
hydrocarbons,  the  following  more  important  ones  may  be  mentioned  : 

(a)  Any  member  of  the  series  may  be  obtained  by  reducing  the  halogen  derivatives 
of  the  hydrocarbon  (obtained  from  the  alcohols  and  the  halogen  hydracids)  by  means  of 
nascent  hydrogen  (generated  by  sodium  amalgam,  or  by  a  solution  of  sodium  in  absolute 
alcohol,  or  by  zinc  and  hydrochloric  acid,  or  by  heating  zinc  and  water  at  160°)  or  of 
hydriodic  acid,  especially  in  the  presence  of  red  phosphorus  (which  transforms  the  iodine 
into  hydriodic  acid) :  C2H5T  +  H2  =  HI  +  C2H6;  C2H5I  +  HI  =  I2  +  C2H6  (see  Table 
of  the  halogen  derivatives  of  the  hydrocarbons). 

(6)  The  alcohols  give  paraffins  when  heated  with  hydriodic  acid  : 

C2H5 .  OH  +  2HI  =  H20  +  I2  +  C2H6. 

(c)  By  the  interaction  of  zinc  alkyls  and  water  : 

Zn(C2H5)2  +  2H2O  =  Zn(OH)2  +  2C2H6. 

(d)  From  unsaturated  hydrocarbons  by  the  action  of  hydrogen,   e.  g.,   by  heating 
acetylene  and  hydrogen  at  400°  to  500°,  or  in  presence  of  platinum-black. 

(e)  By  eliminating  a  molecule  of  carbon  dioxide  from  the  organic  acids  and  salts  by 
heating  with  soda-lime  or  sodium  alkoxide : 

CH3  .  COONa  (sodium  acetate)  +  NaOH  =  Na2C03  +  CH4. 

f. 
(/)  By  the  action  of  sodium  or  of  zinc  on  the  zinc  alkyls  or  alkyl  iodides  in  ethereal 

solution  in  a  closed  tube  (Wurtz),  two  alkyl  groups,  even  different  ones,  being  condensed  : 

(1)  2CH3I  +  Na2  =  2NaI  +  C2H6. 

(2)  C2H5I  +  C4H9I  +  Na2  =  2NaI  +  C2H5  .  C4H9. 

(3)  2CH3I  +  Zn(CH3)2  =  ZnI2  +  2C2H6. 

(g)  During  the  last  few  years  it  has  been  shown  that  magnesium  is  much  more  active 
than  zinc  in  many  organic  syntheses  (see  later,  Grignard  Reaction),  and  with  alkyl  iodides 
dissolved  in  absolute  ether,  magnesium  forms  magnesium  alkyl  salts  which,  in  decom- 
position by  means  of  water  or  dilute  acid  or  ammonia  with  solid  ammonium  chloride,  yield 
the  saturated  hydrocarbons  :  C2H5I  -f  Mg  =  C2H8MgI,  and  this  +  H20  =  CaH6  -(- 
Mg(OH)I.  In  part,  however,  the  magnesium  fixes  the  halogen,  and  then  two  alkyl  residues 
condense,  forming  a  hydrocarbon  of  double  the  number  of  carbon  atoms : 

2C2H5I  +  Mg  -  MgI2  +  C4H10. 

(h)  Sabatier  and  Senderens'  catalytic  process,  for  which  see  p.  35. 
(i)  By  electrolysing  acetic  acid  : 

CH3— COOH  CH3 

.        =     |       +  2C02+H2, 
CH3— COOH  CH3 

the  hydrogen  going  to  the  negative  pole  and  the  hydrocarbon  and  carbon  dioxide  to  the 
positive  one. 

METHANE    (MARSH   GAS),   CH4 

This  is  a  gas  which  is  often  found  ready  formed  in  nature,  and  in  former 
times  it  was  always  confused  with  hydrogen  (inflammable  air).  Pliny  refers 
to  the  gases  which  exude  from  the  earth  in  certain  regions  and  are  inflam- 
mable (these  are  probably  the  sacred  fires  of  the  ancient  Chaldeans).  Basil 
Valentine  (1500)  records  fires  in  mines  preceded  by  the  emanation  of  asphyxi- 
ating, poisonous  vapours,  which  are  dispersed  and  rendered  innocuous  by  the 
.  fire  issuing  from  the  rock.  Also  Libavius  (1600)  speaks  of  the  inflammable 
and  explosive  gas  of  mines,  and  in  1700-1750  history  records  numerous 
explosions,  especially  in  coal-mines.  In  was  Volta  who,  in  1776,  when  studying 
the  same  gas,  which  is  also  evolved  in  marshes,  showed  that  it  differs  from 

VOL.  II.  3 


34 


ORGANIC    CHEMISTRY 


hydrogen,  since  in  burning  it  requires  double  its  volume  of  oxygen  and  forms 
carbon  dioxide.  In  1785  Berthollet  proved  that  the  gas  is  formed  of  carbon 
and  hydrogen,  and  later  Henry,  Davy,  and  Berzelius  determined  its  true 
composition. 

It  occurs  abundantly  as  exhalations  from  the  earth  near  the  Caspian  Sea 
(sacred  fires  of  Baku)  and  in  the  peninsula  of  Apsheron  is  used  for  heating 
purposes. 

At  Pittsburg  there  are  great  wells  of  pure  methane,  and  it  is  found  also 
near  Glasgow,  in  the  Crimea,  and  also  in  Italy,  at  Pietra  Mala  (Bologna),  in 
Ferrarese,  in  Piacenza  (Salsomaggiore),  etc.  It  always  occurs  in  coal-mines, 
being  formed  from  the  coal  by  slow  decomposition  and  remaining  occluded 
in  the  coal  under  great  pressure,  together  with  carbon  dioxide  and  nitrogen 
(see  below  :  Industrial  Uses). 

It  is  invariably  developed  in  marshy  places  where  there  is  organic  matter 
putrefying  under  water.  It  is  found  in  the  gas  of  the  intestines  of  man  and, 
still  more,  of  the  ruminants  (about  50  per  cent.  CH4),  being  produced  by  the 
action  of  enzymes  on  the  cellulose  (C6H1005)  of  vegetable  matter  :  C6H10O5  + 
H20  =  3CO2  +  3CH4.1  Illuminating  gas  contains  up  to  40  per  cent,  of  it. 

PROPERTIES.  It  was  one  of  the  permanent  gases  (Vol.  I.,  p.  29);  it 
liquefies  at  —  164°  and  solidifies  at  —  186°.  It  has  the  sp.  gr.  0'559  and  1  litre 
weighs  0'720  gram.  It  has  no  colour  or  taste,  but  a  faint  garlicky  odour. 
It  dissolves  slowly  but  appreciably  in  fuming  sulphuric  acid,  but  only  very 
slightly  in  water  (0*05  per  cent.).  It  is  readily  inflammable  and  burns  with 
a  faintly  luminous  flame ;  mixed  with  oxygen  (heat  of  combustion,  9433  cals. 
per  cu.  metre ;  see  also  p.  26)  it  forms  a  detonating  mixture  (inflammable  at  667°, 
whilst  the  mixture  with  ethane  inflames  at  616°  and  that  with  propane  at 
547°),  the  maximum  effect  being  obtained  with  1  vol.  of  methane  and  2  vols. 
of  oxygen  (CH4  +  202  =  C02  +  2H20).2  Mixed  with  air,  it  forms  the  fire- 
damp of  coal-mines,  which  is  very  dangerous  owing  to  its  explosibility,3  although 

1  The  percentage  composition  of  intestinal  gas  varies  with  the  nature  of  the  food  taken. 


H 

CH, 


Flesh 
35-5 


Mixed 
25-8 
15-5 


Milk 
64-2 


Vegetable 

1-5 
49-3 


2  Explosive  gas  mixtures  (Teclu,  1907)  : 


Minimum  effect. 

With  excess. 

With  deficit. 

100  volumes  of  air  +  hydrogen 

Vo!s. 
40 

Vols. 

170 

Vols. 
8-10 

+  methane  . 

10 

.  — 

3-6 

+  coal  gas    . 

17-20 

31 

4-7 

+  acetylene 

8-3 

130 

2-4 

+  ether  vapour 

3-3 

8 

1-5 

+  alcohol  vapour 

6-5 

— 

3-4 

3  Since  the  methane  is  occluded  under  great  pressure  between  the  layers  of  coal,  its  develop- 
ment and  hence  also  the  danger  is  greater  when  the  atmospheric  pressure  diminishes  or  when  the 
temperature  rises.  To  prevent  explosions  of  firedamp,  the  miners  use  the  Davy  lamp  (Vol.  I. 
p.  464).  Considerable  danger  of  explosion  more  often  exists  in  mines  owing  to  the  coal  dus\ 
suspended  in  the  air  of  the  galleries  and  behaving  like  a  pyrophoric  substance  (Vol.  L,  p.  189); 
as  a  precautionary  measure,  air  is  continually  circulated  through  the  galleries  by  powerful 
fans,  and  the  air  and  the  walls  are  moistened  by  means  of  pulverisers.  Mines  containing  much 
dust  are  dangerous  even  if  the  Davy  lamp  is  used,  since  the  particles  of  coal  passing  through  the 
gauze  into  the  lamp  may  issue  in  a  red-hot  condition.  Hardy  has  constructed  an  apparatus 
which  allows  of  the  quantity  of  methane  being  determined  from  the  sound  produced^by  the 
mixture  of  air  and  methane  in  traversing  an  organ  pipe. 

In  1913  Haber  and  Leiser  improved  the  apparatus  into  the  firedamp  whistle,  which  allows 
the  sound  produced  with  pure  air  to  be  compared  at  any  instant  with  that  given  by  the  methane- 


METHANE     IN     NATURE  35 

it  is  not  poisonous,  since  miners  can  withstand  an  atmosphere  containing  9  per 
cent,  of  methane ;  if  there  is  not  more  than  this  proportion,  it  produces  a  kind 
of  pressure  at  the  forehead,  which  ceases  immediately  pure  air  is  breathed.  ' 

By  an  electric  discharge  or  in  a  red-hot  tube,  it  decomposes  into  carbon  and 
hydrogen,  and  a  few  unsaturated  hydrocarbons,  with  traces  of  benzene  and 
naphthalene. 

PREPARATION  IN  THE  LABORATORY.  Besides  by  the  general  methods 
given  above,  methane  is  formed  by  passing  a  mixture  of  carbon  monoxide  or 
dioxide  with  hydrogen  over  reduced  nickel  (catalyst)  heated  at  250°  (Sabatier 
and  Senderens)  :  CO  -j-  3H2  =  H20  +  CH4  (see  note,  p.  58).  Attempts  have 
recently  been  made  to  put  this  method  on  an  industrial  basis,  by  transforming 
the  carbon  monoxide  and  dioxide  of  water-gas  into  methane  (Ger.  Pat. 
183,412).  Pure  methane  is  "formed  by  passing  a  mixture  of  carbon  disulphide 
vapour  and  hydrogen  sulphide  over  red-hot  copper  (Berthelot)  :  CS2  + 
2H2S  -|-  8Cu  =  4Cu2S  +  CH4 ;  also  by  treating  aluminium  carbide  with 
water  :  C3A14  +  12H20  =  4A1(OH)3  +  3CH4. 

Ipatiev  obtains  methane  by  heating  carbon  in  presence  of  excess  of  hydrogen 
at  520°,  reduced  nickel  (with  CO2  and  H2  the  reaction  is  less  complete)  being 
used  as  catalyst. 

In  the  laboratory  it  is  usually  prepared  from  an  intimate  mixture  of  one  part  of  crys- 
talline sodium  acetate  with  four  parts  of  soda-lime  (or  better,  with  four  parts  of  baryta  or 
with  a  mixture  of  anhydrous  sodium  carbonate  and  dry  powdered  calcium  hydroxide). 
This  is  heated  in  a  retort  or  in  a  hard  glass  tube  until  gas  begins  to  be  evolved,  the 
temperature  being  then  kept  constant.  As  impurities,  it  contains  a  little  hydrogen  and 
acetylene,  so  that,  before  collecting  the  methane,  the  gas  is  passed  over  pumice  moistened 
with  concentrated  sulphuric  acid. 

Chemically  pure,  it  may  be  obtained,  by  the  general  method,  from ,  zinc  ethyl  and 
water. 

INDUSTRIAL  USES.  For  several  centuries,  the  inflammable  gases  issuing  from  the 
earth  and  from  petroleum  have  been  utilised  at  Baku  for  heating  lime-kilns,  and  nowadays 
are  employed  for  various  other  industrial  and  domestic  purposes.  The  amounts  of  natural 
gas  used  at  Baku  were  46-5  million  cu.  metres  in  1905,  96-3  million  in  1906,  and  117  million 
in  1907,  the  composition  being :  CO2,  3  to  3-8  per  cent. ;  CnHm,  1-2  to  2-6  per  cent. ;  0, 
7  to  7-6  per  cent. ;  CH4,  54-8  to  60-2  per  cent. ;  H,  13-58  to  0-8  per  cent. ;  and  N,  20-4  to  25 
per  cent.  In  North  America,  as  far  back  as  1821,  these  natural  emanations  were  used  as 
illuminating  gas.  The  most  important  discoveries,  made  at  Pittsburg  in  1882,  resulted 
in  98  per  cent,  of  the  American  production  being  obtained  from  this  source  in  1900;  after 
1905,  the  wells  of  Louisiana  also  acquired  importance,  and  later  the  greatest  output  was 
obtained  in  the  state  of  Kansas  (to  the  value  of  £440,000  in  1905  and  £1,520,000  in  1908). 
At  St.  Louis  300,000  cu.  metres  were  consumed  per  day  in  1910. 

In  1912  the  wells  of  Caddo,  near  Shreveport  (Louisiana),  yielded  as  much  as  280,000  cu. 
metres  per  day  of  gas  (95  per  cent.  CH4,  2-56  per  cent.  N,  2-34  per  cent.  CO2,  0-01  per  cent. 
H),  these  wells  being  about  300  metres  deep  and  the  gas  being  furnished  at  a  pressure  of 
about  40  atmospheres.  The  gas  is  led  in  mains  to  Shreveport  and  sold  at  5  cents  per  cu. 
metre  for  domestic  purposes  and  at  about  2  cents  for  industrial  uses,  this  allowing  electrical 
energy  to  be  obtained  more  cheaply  than  from  Niagara  Palls.  The  utilisation  of  the  gas  at 

air  mixture  and  is  capable  of  detecting  0-2  to  0-5  per  cent,  of  methane.  Observation  of  the 
luminous  aureole  formed  round  the  flame  of  a  safety  lamp  with  a  slightly  twisted  wick  is  not 
capable  of  revealing  differences  of  2  to  3  per  cent,  of  CH4>  so  that  the  explosive  limit  (5-5  per 
cent,  of  CH4)  may  be  reached  without  discovery  in  this  way. 

When  mines  are  being  excavated,  safety  explosives  (which  see)  are  used  to  avoid  fires  and 
explosions.  Sometimes. the  coal  ignites  in'certain  parts  of  the  mine;  in  such  cases,  work  is  not 
suspended,  but  these  parts  are  isolated  byi  walls,  and  if  the  fire  becomes  threatening,  recourse  is 
had  (usually  with  success)  to  the  sealing  of  the  mine  and  subsequent  inundation  with  water  or 
filling  of  the  galleries  with  carbon  dioxide.  When  an  explosion  occurs  in  a  mine,  a  large  amount 
of  carbon  monoxide  is  formed,  which  poisons  the  workers,  who  can,  however,  sometimes  be  saved 
if  they  can  be  made  to  breathe,  sufficiently  promptly,  under  a  bell  containing  compressed  air 
(Mosso's  Method;  Vol.  I.,  p.  190). 


36  ORGANIC    CHEMISTRY 

the  present  day  is  carried  out  rationally  and  on  a  vast  industrial  scale,  the  gas  (issuing 
from  suitably  constructed  wells)  passing  to  large  gasometers  which  distribute  it  directly 
to  factories  and  houses,  where  it  is  employed  for  power,  heating,  and  lighting  (with  the 
Auer  mantle),  the  price  being  about  3J  cents  per  cubic  metre. 

The  gas  utilised  in  the  United  States  of  America  represents  the  following  values  in 
pounds  sterling:  in  1882,  40,000;  in  1890,  1,400,000;  in  1894,  2,800,000;  in  1899, 
4,000,000;  in  1906,  9,600,000;  in  1908,  11 '4  milliards  of  cu.  metres  were,  used  and  in 
1911,  15  milliards  (£14,000,000).  These  gases  have  the  sp.  gr.  0-624  to  0-645,  and  a 
calorific  value  of  about  9000  cals.  per  cu.  metre.  The  composition  varies  between  the 
following  limits :  CH4,  80  to  95  per  cent. ;  H,  0-5  to  1-5  per  cent,  (sometimes  15  per 
cent.) ;  C2H4,  0-3  to  4  per  cent. ;  CO,  0  to  0-6  per  cent. ;  CO2,  0-3  to  2-5  per  cent. ;  O,  0-35 
to  0-80  per  cent. ;  N,  0-5  to  3-5,  together  with  traces  of  H2S. 

In  Canada,  400  wells  are  being  used,  giving,  in  1907,  gas  of  the  value  of  £1 20,000.  In 
England,  wells  have  been  sunk  since  1900  which  yield  400,000  cu.  metres  of  gas  per  day. 
The  spring  at  Wels,  in  Austria,  which  gave  57,000  cu.  metres  of  gas  per  day  in  1894,  yielded 
only  500  cu.  metres  per  day  in  1901. 

At  Kissarmas,  near  Sarmas  (Hungary),  a  well  yielded  in  1909  1,700,000  cu.  metres  of 
almost  pure  methane  per  twenty-four  hours  at  a  pressure  of  30  atmospheres.  The  first 
source  of  natural  gas  in  Germany  was  discovered  in  1910  at  Neuengamme  at  a  depth  of  248 
metres,  the  gas  issuing  at  25  atmospheres'  pressure  and  maintaining  for  a  long  time  the  per- 
centage composition  :  CH4,  91-6 ;  H,  2-3 ;  C02,  0-2 ;  O,  0-7 ;  N,  4-4 ;  heavy  hydrocarbons,  0-8. 
The  gases  obtained  from  the  deposits  of  potash  salts  at  Stassfurt  (see  Vol.  I.,  p.  530)  have 
a  varying  composition :  CH4,  5  to  40  per  cent. ;  H,  1 1  -  to  80  per  cent. ;  N,  up  to  40  per 
cent. ;  helium  and  neon,  1  per  cent.  The  value  of  these  methane  springs  may  be  estimated 
from  the  fact  that  one  ton  of  coal  yields  only  300  cu.  metres  of  gas. 

The  gas  which  is  used  at  Salsomaggiore  (Piacenza)  for  public  lighting  purposes  and  which 
issues  from  the  earth  together  with  petroleum  and  saline  waters  containing  iodine,  has 
the  sp.  gr.  0-692,  and  the  following  percentage  composition  (Nasini  and  Anderlini, 
1900) :  CH4,  68;  C2H6,  21 ;  heavy  hydrocarbons,  1 ;  N,  8.  In  Italy,  1,520,000  cu.  metres 
of  these  gases,  of  the  value  £2280,  were  used  altogether  in  1902,  6,737,500  cu.  metres  in 
1908,  and  8,270,000  cu.  metres,  of  the  value  £8760,  in  1909. 

Important  sources  of  these  gases  have  been  recently  discovered  in  Hungary  (in  1911  at 
Klausenburg,  where  the  well  gave  800,000  cu.  metres  per  day  of  gas  containing  99  per  cent, 
of  methane  in  1913),  England  (at  Heathfield  a  well  gave  as  much  as  500,000  cu.  metres  per 
day),  and  in  Denmark  (since  1872). 

ETHANE,   C2H6 

This  gas  is  found  dissolved  in  crude  petroleum,  and  is  one  of  the  principal  constituents 
of  the  North  American  gas-wells  of  Delamater,  near  Pittsburg. 

It  is  a  gas  which  can  be  liquefied  at  0°  by  means  of  a  pressure  of  24  atmospheres  and 
then  has  the  sp.  gr.  0-446 ;  at  the  ordinary  pressure  it  becomes  liquid  and  boils  at  —  84° 
and  is  solid  and  melts  at  —  172°.  It  is  almost  insoluble  in  water ;  1  vol.  of  absolute  alcohol 
dissolves  1  \  vols.  of  it.  It  burns  with  a  faintly  luminous  flame,  and  is  more  readily  soluble 
than  methane.  In  the  laboratory  it  is  prepared  by  the  general  methods  already  given 
(p.  33). 

PROPANE,   C3H8   (METHYLETHYL,   CH3'C2H5   or 
DIMETHYLMETHANE,   CH2(CH3)2) 

This  is  a  gas  like  ethane  and  becomes  liquid  at  —  44°,  or  under  5  atmospheres'  pressure 
at  0°,  the  liquid  at  0°  having  the  sp.  gr.  0-535 ;  it  solidifies  and  melts  at  —  45°.  It  is  slightly 
soluble  in  water,  and  absolute  alcohol  dissolves  6  vols.  of  it.  With  water  under  pressure 
and  at  temperatures  below  0°  it  forms  a  solid  hydrate,  which  decomposes  at  +  8-5°.  The 
illuminating  power  of  propane  is  about  \\  times  that  of  ethane.  It  is  best  prepared,  in 
the  laboratory,  by  reducing  isopropyl  iodide  by  means  of  the  copper-zinc  couple,  or  by 
reducing  acetone  or  glycerol  with  hydriodic  acid  : 

C3H5(OH)3+  6H=  3H2O+  C3H8      or      CH3  •  CO  •  CH3  +  4H  =  H2O  +  C3HS. 

glyceroi  acetone 


HIGHER     PARAFFINS  37 

BUTANES,   C4H10    (Two  Isomerides) 

(a)  Normal  Butane,  CH3  •  CH2  •  CH2  •  CH3  (diethyl),  is  a  gas  which  liquefies  at  -f-  1°, 
and  at  0°  has  the  sp.  gr.  0-600.     It  is  found  in  Pennsylvanian  petroleum,  and  is  prepared 
in  the  laboratory  by  the  ordinary  methods  (p.  33). 

CTT 

(b)  Isobutane,  CH3  •  CH<nH.3   (trimethylmethane  or  methylpropane),  is  a  gas  which 

(jtl3 

becomes  liquid  at  —  115°;  it  is  contained  in  petroleum  and  is  prepared  by  the  usual 
methods  in  the  laboratory. 

PENTANES,   C5H12 

x 

These  hydrocarbons  are  found  especially  in  the  petroleum  products  boiling  a  little 
above  0°,  and  are  placed  on  the  market  under  the  names  of  rhigolene  and  cymogen  for 
anaesthetic  purposes  and  for  the  manufacture  of  artificial  ice.  The  three  isomerides 
predicted  by  theory  are  known  : 

(a)  Normal  pentane,  CH3  •  [CH2]3  •  CH3,  is  a  colourless,  mobile  liquid  boiling  at  -f  37-3°, 
having  the  sp.  gr.  0454  at  0°,  and  solidifying  only  at  about  —  200°  ;  it  is  hence  used  for 
making  low-temperature  thermometers,  and  as  a  lubricant  in  the  Claude  liquid  air  machine 
(Vol.  I.,  p.  345).     It  occurs  abundantly  in  Pennsylvanian  petroleum. 

(b)  Isopenfane,  CH3  •  CH  •  CH2  •  CH3  (methyl-2-butane  or  ethylisopropyl),  is  a  light 

CH3 

colourless  liquid  boiling  at  30-4°,  and  having  the  sp.  gr.  0-622  at  20°.  It  is  found  in  large 
quantities  in  petroleum,  and  may  be  prepared  artificially  from  isoamyl  iodide  by  the 
ordinary  methods  (p.  33). 

riTT  /-ITT 

(c)  TetramethylmetJwme,  r,Tr3!>C<;riT_r3  (dimethyl-2-propane),  is  found  in  the  gases  from 

UrL3  OrL3 

petroleum,  and  is  liquid  at  -f  9°  and  solid  at  —  20°.  It  may  be  obtained  in  the  laboratory 
either  by  chlorinating  acetone,  CH3  •  CO  •  CH3,  by  means  of  phosphorus  pentachloride 
and  treating  the  dichloropropane  thus  formed  with  zinc  methyl  : 


„  ^3 
CH3  C1  +       <CH3  ~          2      CH3  CH3 

or  from  tertiary  butyl  iodide  by  the  action  of  zinc  methyl  :__ 


j       _  ^3       „  T        „ 
CH3I  <CH3-  2CH3CH3 

The  constitutions  of  acetone  and  tertiary  butyl  iodide  having  been  determined  (see  later), 
that  of  tetramethylmethane  is  fixed,  and,  since  the  reduction  of  butyl  iodide  yields  isobutane, 
the  constitution  of  the  latter  is  proved. 

HEXANES,   C6H14 

The  five  isomeric  hexanes  which  should  exist  are  all  known  (see  Table,  p.  32).  They 
are  found  particularly  in  petroleum  ether,  gasolene,  and  ligroin  (i.  e.,  in  the  portions  of 
petroleum  boiling  below  150°),  together  with  heptanes  and  octanes.  They  are  formed  also 
from  shaly  coal  like  cannel  coal  and  boghead. 

HIGHER   HYDROCARBONS 

These  are  very  numerous  and  are  found  in  petroleum  and  in  its  residues  (vaseline, 
paraffin  wax,  etc.)  ;  they  distil  unchanged  (after  C16)  only  in  a  vacuum,  the  boiling-point 
being  thus  lowered  by  about  100°. 

Many  of  these  higher  normal  hydrocarbons  were  prepared  synthetically  by  Krafft  by 
reducing  the  corresponding  fatty  acids,  alcohols,  and  ketones.  They  are  generally  soluble 
in  ether,  petroleum  benzine  and,  partly,  petroleum  itself,  but  are  insoluble  or  almost  so  in 
alcohol,  acetone,  acetic  acid,  acetic  anhydride,  etc. 

HEPTACOSANE,  C2;H56,  and  HENTRIACONTANE,  C31H64,  are  found  in  beeswax 
and  in  American  tobacco  (about  l.per  cent.),  the  former  being  also  found  in  soot. 

HEXACONTANE,  C60H122,  is  the  highest  term  of  the  paraffin  series  to  be  prepared 
synthetically  by  Hell  and  Hagele  in  1889  by  condensing  2  mols.  of  myricyl  iodide,  C30H61T, 
by  fusion  with  sodium,  which  removes  the  iodine  as  Nal,  It  melts  at  102°,  is  slightly 


38  ORGAN  1C    CHEMISTRY 

soluble  in  alcohol  or  ether,  and  distils,  to  some  extent  unchanged,  in  a  vacuum.  It  has 
probably  the  normal  structure  and  thus  forms  the  longest  carbon  atom  chain  as  yet  prepared 
synthetically. 

Some  of  the  saturated  hydrocarbons  of  the  aliphatic  series  have  important 
practical  applications,  especially  as  sources  of  light  and  heat.  In  illuminating 
gas  are  found  the  gaseous  members,  in  petroleum  the  liquid,  and  in  paraffin 
wax  the  solid  ones. 

A  brief  account  of  the  industrial  treatment  of  these  three  products  will 
now  be  given. 

ILLUMINATING  GAS1 

Illuminating  gas  and  the  other  products  of  the  dry  distillation  of  coal  vary  in  com- 
position with  the  nature  of  the  coal  employed.  In  gas  manufacture,  account  has  to  be 

1  History.  This  industry  began  with  the  nineteenth  century,  its  apotheosis  being  reached 
at  the  end  of  that  century  with  the  application  of  the  incandescent  gas-mantle.  From  the  year 
900  the  Chinese  have  employed  petroleum  vapour,  distributed  by  wooden  pipes,  for  lighting 
purposes.  It  was,  however,  only  in  1739  that  James  Clayton,  in  investigating  the  causes  of 
the  emanation  pf  inflammable  gas  often  occurring  in  the  Lancashire  mines,  heated  coal  in  closed 
vessels  and  collected  the  gas  (illuminating  gas  !)  developed  in  large  bladders.  In  1767,  Watson, 
in  laboratory  experiments  on  a  small  scale,  obtained  gas,  ammonia,  and  coke  by  the  distillation 
of  coal.  This  was  the  time  when  coke  was  beginning  to  be  employed  in  metallurgical  operations, 
and  in  1786  Lord  Dundonald  used  the  gas  from  the  coke  furnaces  to  light  his  house,  and  Pickel 
lighted  his  own  laboratory  with  the  gas  formed  on  distilling  bones.  More  important  trials  were, 
however,  made  in  Great  Britain  by  W.  Murdock  (or  Murdoch ),  for  the  illumination  of  large  works 
by  distilling  coal.  Helped  in  his  undertaking,  first  by  Watt,  the  inventor  of  the  steam-engine, 
and  afterwards  by  his  pupil  Clegg,  he  succeeded  in  1805  in  extending  lighting  by  gas  to  many 
establishments.  The  distillation  of  wood  was  studied  by  the  engineer  Lebon,  in  France,  and  in 
1799,  a  patent  was  taken  out  "  for  a  new  method  of  employing  fuel  more  efficiently,  for  heating 
or  lighting,  and  of  collecting  the  various  products."  Some  days  later,  all  Paris  was  admiring 
the  gas-lamp  which  Lebon  used  to  illuminate  the  gardens  of  the  Hotel  Seignelay.  Probably 
Lebon  did  not  then  foresee  the  wonderful  development  which  was  to  take  place  in  gas  lighting 
in  the  nineteenth  century,  or  dream  of  the  monument  to  be  erected  to  him  many  years  later  in 
his  native  town,  Chaumont,  or  of  the  statue  which  was  dedicated  to  him  in  Paris  in  1905. 

It  was  when  the  use  of  large  plant  was  attempted  for  lighting  by  gas  that  technical  difficulties 
cropped  up,  inconveniences  which  were  negligible  on  a  small  scale  becoming  insurmountable  in 
the  case  of  large  works.  It  was  already  noticed  that  the  new  illuminating  gas  burned  with  a 
rather  sooty  flame  and  disseminated  unpleasant  odours,  whilst  in  the  works  the  piping  often 
became  obstructed  owing  to  solid  distillation  products  being  carried  by  the  gas.  If,  in  addition, 
we  consider  the  popular  prejudice  to  any  innovation,  aggravated  by  the  fantastic  propaganda  of 
certain  scientific  men,  especially  in  France,  who  exaggerated  the  danger  of  explosion,  it  is  easy  to 
conceive  how  unpromising  the  conditions  of  this  industry  were  up  to  1812.  To  Clegg  is  due  the 
elimination  of  the  main  technical  difficulties,  the  tarry  matters  carried  along  by  the  gas  being 
removed  by  means'  of  a  number  of  cooled  tubes,  and  further  purification  being  effected  by  lime, 
the  gas  being  then  collected  in  large  gasometers,  from  which  it  was  distributed  by  pipes  to  the 
consumers.  Thus,  it  became  possible  in  1813  to  light  part  of  London  with  coal  gas,  and  in  1815 
Winsor  illuminated  certain  quarters  of  Paris.  In  1816  Bartolomeo  Bizio  lighted  the  portico  of 
the  Academy  of  Fine  Arts  in  Florence  with  gas  distilled  from  wood. 

Nobody  on  the  Continent  dared  attempt  a  similar  industry;  everybody  was  distrustful, 
not  foreseeing  its  great  future  and  being  frightened  by  the  technical  difficulties  which  met  this,  the 
first  great  chemical  industry,  which  was  thus  for  many  years  confined  to  England.  It  was  in 
this  country  that  it  underwent  the  most  rapid  extension  and  perfection  (in  1823,  fifty -two  towns 
were  lighted  by  gas),  the  scientific  and  practical  men  giving  it  their  entire  support.  In  1810  a 
powerful  English  company  was  founded  by  Clegg  and  became  later  the  famous  Imperial  Contin- 
ental Gas  Association,  which,  with  a  capital  of  £2,000,000  in  1824,  £3,500,000  in  1874,  £3,800,000 
in  1897,  and  £5,000,000  in  1908,  was  formed  with  the  view  of  undertaking  the  lighting  of  the 
principal  European  towns.  Even  to-day  many  towns  are  still  pledged  to  contracts,  as  yet 
unexpired,  with  the  great  English  companies.  London  itself,  within  the  last  few  years,  has  found 
the  greatest  obstacle  to  the  introduction  of  electric  lighting  in  contracts  with  gas  companies 
which  have  already  made  fabulous  profits. 

In  Germany,  the  first  small  gas-plant  was  that  of  Lampadius  in  1816,  used  for  his  own  establish- 
ment, extension  being  subsequently  effected  as  a  result  of  the  work  of  Flashoff  and  Dinnendhal. 
At  Berlin  the  first  attempt  was  made  in  1826;  then  followed  Hanover,  and  in  1884,  557  German 
towns  were  lighted  by  gas,  the  annual  consumption  of  coal  being  1,700,000  tons.  In  Austria  the 
first  plant  was  erected  in  1818  by  Prechtl.  In  America,  Baltimore  was  illuminated  by  gas  in 
1806,  Philadelphia  in  1822,  and  New  York  in  1834.  At  Milan  gas  lighting  was  introduced  in  1832. 

After  1870  all  the  principal  populous  centres  and  even  the  small  towns  were  lighted  by  gas, 
all  objection  to  this  form  of  illumination  having  disappeared ;  experience  had  shown  that  the 
expected  terrible  explosions  of  mixtures  of  gas  and  air  did  not  occur,  and  that  the  small  accidents 
which  did  happen  were  not  more  serious  than  those  occurring  daily  with  paraffin  lamps.  The 


LIGHTINGGAS  39 

taken  of  the  value  of  the  by-products  :  coke,  tar,  ammonia,  etc.,  which  sometimes  con- 
tribute largely  to  the  cost  of  manufacture.  Consequently,  mixtures  of  coal  are  used  which 
give  good  coke,  the  luminosity  of  the  gas  from  certain  coals  being  supplemented  by  mixing 
with  others  rich  in  hydrogen  and  bitumen,  such  as  some  English  coals,  like  cannel  coal, 
boghead,  various  shaly  coals,  etc. ;  these  are,  however,  very  expensive  and  have  not  been 
used  during  recent  years,  since  the  luminosity  is  now  obtained  by  means  of  incandescent 
mantles  (Auer) .  In  general,  coals  used  for  making  gas  have  percentage  compositions  vary- 
ing between  the  following  limits  :  C,  78  to  85;  H,  5  to  8;  0,6  to  13;  N,  1-2  to  1-9;  and  S, 
0-1  to  2,  a  higher  content  of  sulphur  being  harmful ;  they  should  leave  little  ash  on  burning, 
and  preference  is  given  to  those  yielding  considerable  quantities  of  volatile  products. 
The  more  hydrogen  there  is,  the  greater  will  be  the  useful  yield,  since  every  kilogram  of 
hydrogen  can  gasify  4  to  5  kilos  of  carbon  (according  as  more  or  less  methane,  ethylene, 
etc.,  is  formed).  Gas-coal  giving  good  coke  contains  more  than  15  per  cent,  and  less  than 
35  per  cent,  of  volatile  products. 

The  oxygen  present  in  coal  gives  rise  to  larger  or  smaller  quantities  of  carbon  dioxide 
and  monoxide,  the  latter  being  a  powerful  poison  (see  later,  p.  58).  Only  10  to  15  per  cent, 
of  the  nitrogen  present  in  the  coal  is  transformed  into  ammonia,  20  per  cent,  being  found  in 
the  gas  and  60  per  cent,  in  the  coke,  whilst  2  to  3  per  cent,  forms  hydrocyanic  acid  and 
cyanides  in  the  gas  and  tar.  Moisture  in  the  coal  is  harmful,  since  water  causes  an  increase 
in  the  amount  of  carbon  dioxide  in  the  gas  and  also  absorbs  heat  for  its  evaporation. 

In  order  to  judge  of  the  value  of  the  coal,  distillations  are  carried  out,  in  gasworks, 
in  small  laboratory  retorts  containing  a  weighed  quantity  of  coal  and  heated  at  a  very 
high  temperature  (900°  and  even  higher) ;  the  gas  and  vapours  are  washed  in  bottles, 
first  with  lime-water  and  then  with  lead  acetate,  the  pure  gas  being  collected  in  a  cylinder 
over  mercury,  so  that  it  may  be  measured  and  its  composition  and  illuminating  power 
investigated.  In  general  the  laboratory  test  gives  a  yield  of  gas  somewhat  lower  than 
that  obtained  in  the  large  works  retorts,  since  in  the  latter  the  tar  also  undergoes  partial 
decomposition  and  gasification ;  in  laboratory  tests  it"  is,  therefore,  necessary  to  raise  the 
temperature  very  gradually  and  to  heat  strongly  only  at  the  end. 

To  judge  of  the  practical  value  of  a  coal,  use  is  made  of  the  product  of  the  yield  of  gas 
(that  is,  the  number  of  cubic  metres  from  100  kilos  of  coal)  and  its  candle-power.  For  any 
given  coal,  this  product  is  almost  constant,  increase  of  the  temperature  of  distillation 
resulting  in  a  greater  yield  of  gas,  but  of  a  lower  illuminating  power.  Naturally  this  rule 
holds  only  between  certain  limits  of  temperature,  which  are  never  exceeded  in  practice. 

Of  various  coals,  the  best  is  that  which  gives  the  highest  value  for  this  product,  but 
account  must  also  be  taken  of  the  yields  of  coke,  ammonia,  and  tar,  and  of  the  specific 
gravity  of  the  gas. 

The  temperature  of  carbonisation  varies  with  the  nature  of  the  coal,  and,  in  general, 
with  fatty  coals  (bituminous)  the  evolution  of  gas  begins  at  50°,  and  at  a  red  heat  vapours 
of  liquid  products  pass  over;  at  a  higher  temperature,  gaseous  products  predominate. 

The  most  convenient  temperature  usually  lies  between  red  heat  (cherry-red)  and 
yellowish  white  heat.  In  general,  after  an  hour's  heating  (with  a  furnace  at  1400°),  the 
coal  in  the  retort  reaches  400°,  after  three  hours  950°,  and  after  five  hours  1075°.  On  heating 
1000  kilos  of  English  coal  at  different  temperatures  the  following  results  are  obtained : 

At  dull  red  At  bright  orange 

heat.  red. 

(a)  Gas  obtained  (cubic  metres)  .          .          .  234  340 

(6)  Candle-power       .         .         .      -  .         .         .  20-5  15-6 

(c)  Candles  per  1000  kilos  =  a  X  b      .          .          .  4800  5300 

(d)  Composition :  Hydrogen        ....  38-1%  48    % 

Carbon  monoxide    .          .          .  8-7%  14    % 

Methane          ....  42-7%  30-7% 

Heavy  hydrocarbons         .          .  7-6%  4-5% 

Nitrogen          ....  2-9%  2-8% 

Gas  prepared  at  a  higher  temperature  has  a  lower  calorific  power. 

victory  over  petroleum,  although  furiously  contested,  was  especially  complete  in  the  case  of 
public  lighting. 

To  this  success  have  contributed,  most  of  all,  the  incessant  improvements  of  methods  of  manu- 
facture which  have  resulted  in  the  supply  of  a'purer,  more  abundant,  and  more  economical  gas. 


40 


ORGANIC    CHEMISTRY 


The  composition  of  gas  varies  also  according  as  the  heating  is  more  or  less  prolonged. l 
It  will  be  seen  that  the  diminution  of  luminosity  is  less  proportionally  than  the  increase 
in  volume  of  the  gas,  and  to-day  the  distillation  is  pushed  to  a  temperature  of  1 100°  to  1200°, 
this  resulting  in  greater  (absolute,  not  relative)  quantities  of  light,  luminous  hydrocarbons 
and  of  hydrogen  being  obtained.  It  is  hence  important  to  employ  suitable  mixtures  of 
coals,  so  that  these  may  be  impoverished  as  much  as  possible  at  a  high  temperature,  the 
relatively  low  luminosity  being  compensated  for  by  the  addition  of  special  fatty  coals, 
as  already  mentioned,  and  also,  at  the  present  day,  of  benzene. 

The  duration  of  the  distillation  varies  from  three  to  five  hours ;  the  extra  amount  of  gas 
that  would  be  obtained  by  heating  further  would  be  insufficient  to  make  up  for  the  cost 
of  heating.  Further,  less  and  leaner  coke  is  obtained ;  nowadays  the  tendency  is  to  produce 
a  coke  containing  at  least  8  per  cent,  of  volatile  products,  since  this  burns  more  easily 
for  domestic  heating.  One  hundred  kilos  of  Westphalian  coal  give  about  71  kilos  of  coke, 
4  kilos  of  tar,  5  kilos  of  ammonia  liquors,  and  17  kilos  (30-5  cu.  metres)  of  gas;  loss, 
3  kilos. 

The  COMPONENTS  OF  ILLUMINATING  GAS  obtained  from  coal  are 
very  varied  and  may  be  embraced  in  three  groups  :  (a)  H,  CH4,  CO;  (b)  light- 
yielding  gases  and  vapours  :  ethane,  ethylene,  butylene,  acetylene,  crotonylene, 
allylene,  pentylene,  benzene,  toluene,  xylene,  thiophene,  styrene,  indene, 
naphthalene,  acenaphthene,  fluorene,  propane,  butane,  pyridiiie,  phenols ; 
(c)  inert  or  harmful  impurities  :  CO2,  NH3,  HCN,  SH2,  CS2,  COS,  N,  etc. 
Naturally  the  majority  of  these  substances  are  present  only  in  traces. 

The  percentage  composition  by  volume  of  the  gas  usually  varies  between  the 
following  limits  :  C02,  1-25  to  3'20;  CO,  4'5  to  6'5  (for  English  coals,  6  to  9, 
and  for  German  coals,  occasionally  9  to  11) ;  H,  42  to  55 ;  CH4,  32  to  38 ;  N, 
1  to  3  ;  O,  0  to  0*5 ;  aromatic  hydrocarbons  (benzene,  etc.),  0'8  to  1'4 ;  unsatur- 
ated  hydrocarbons  (ethylene,  2  to  2'5;  acetylene,  O'l  to  0-2;  propylene,  0'2" 
to  0'5,  etc.).  The  specific  gravity  of  gas  varies  from  0'350  to  0'550  (air  =  1) 
and  1  cu.  foot  of  gas  weighs  rather  more  than  half  an  ounce.2  The  calorific  power 
of  illuminating  gas  ranges,  as  a  rule,  from  4000  to  5000  cals.  per  cubic  metre, 
thus  producing  the  same  heating  effect  as  3 '4  kw. -hours.  One  cu.  metre 
of  gas  requires  for  its  complete  combustion  about  5 '5  cu.  metres  of  air  (less  if 
mixed  with  water-gas,  1  cu.  metre  of  this  needing  only  2%3  cu.  metres  of  air). 

In  addition  to  the  lighting  power  (see  later,  p.  62),  for  which  it  is  mostly 
used,  to  the  heating  power,  which  makes  it  a  valuable  source  of  mechanical 
energy  for  gas  engines  (see  p.  60),  to  the  relatively  low  specific  gravity,  which 
renders  it  useful  in  aeronautics,  attention  must  be  paid  to  the  explosive  pro- 
perties of  illuminating  gas  when  mixed  with  air  (see  p.  34),  and  to  its  poisonous 
properties  even  when  present  in  only  2  per  cent,  by  volume.  Its  poisoning 

1  Wright  analysed  the  gas  for  three  different  periods,  starting  from  the  beginning  of  the  distil- 
lation, and  V.  B.  Lewes  (1911)  analysed  the  gas  generated  at  500°  and  at  1000°,  the  results  being  : 


After 
40  minutes. 

After 
three  hours, 

After 
six  hours. 

At  500°. 

At  1000°. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

H2S 

0-4 

0-78 

0-38 

— 

.  —  . 

C02 

2-08 

1-34 

0-59 

2-5 

1-1 

CO  . 

4-52 

6-73 

7-52 

7-3 

6-2 

CH4 

56-46 

37-46 

14-61 

48 

13 

H    . 

25-36 

48-36 

71-94 

27-5 

71 

Heavy  hydrocarbons 

8-51 

3-13 

2-78 

13-5 

7 

N    .         . 

2-37 

2-20 

2-18 

1-6 

1-7 

2  By  passing  ordinary  gas  into  a  retort  filled  with  coke  at  1200°  or  a  higher  temperature,  a 
new  gas,  deprived  of  heavy  hydrocarbons,  oxygen,  and  carbon  dioxide,  very  poor  in  methane 
(6  per  cent. ),  rather  richer  in  carbon  monoxide  (7  to  8  per  cent. )  and  very  rich  in  hydrogen  (up  to 
84  per  cent. )  is  obtained.  This  new  gas  can  be  used  for  aeronautical  purposes,  its  specific  gravity 
being  about  0-23  (Continental  Gas  Gesellschaft,  Dessau,  1910.  See  also  note,  p.  58). 


RETORTS 


41 


effect  is  due  especially  to  the  carbon  monoxide  present  (see  pp.  43,  58),  but  also, 
to  some  extent,  to  other  components.  When  the  first  symptoms  of  poisoning 
are  observed,  fatal  consequences  may  be  prevented  by  vigorous  respiration 
of  pure  air  or,  better,  oxygen,  while  the  use  of  compressed  air  according  to 
Mosso's  system  also  gives  good  results  (Vol.  I.,  p.  190). 

RETORTS.  Murdoch's  first  retorts  were  of  cast-iron,  placed  vertically  in  a  furnace 
(Fig.  44),  but  as  it  was  inconvenient  to  charge  them  Murdoch  introduced  inclined  retorts 
(Fig.  45),  which  he  changed  later  into  horizontal  retorts  of  cast-iron  (Fig.  46). 


FIG.  44. 


FIG.  46. 


In  1820  J.  Graf  ton  suggested  the  use  of  horizontal  retorts  of  fireclay,  since  these  resist 
heat  better,  cost  less,  and  last  longer.  The  most  convenient  form  was  that  with  a  Q  -shaped 
or  elliptical  section  (Fig.  47),  and  the  most  suitable  dimensions  for  these  horizontal  retorts 
were  found  to  be  :  width  of  the  mouth,  43  to  53  cm.,  height  at  the  middle,  31  to  38  cm., 
and  length,  2  to  3  metres.  One  end  was  closed  and  the  mouth  was  swollen  at  the  edge, 
which  carried  screws  serving  to  fix  the  metal  cover  fitted  with  the  delivery  tube.  These 
retorts  were  charged,  according  to 
their  capacity,  with  100  to  200 
kilos  of  coal,  broken  into  uniform 
lumps.  Various  mechanical  con- 
nections were  devised  to  allow  of 
the  retort  being  charged  and  dis- 
charged rapidly  and  with  the  least 
expense  for  hand  labour,  and  one 
of  the  best  arrangements,  with 
a  battery  of  retorts  placed  in 
furnaces  over  gas  producers,  is 
that  shown  in  Fig.  48.  However, 
since  1890  it  has  become  general 
in  the  principal  European  towns 
to  use  inclined  retorts  of  elliptical 
section,  which  were  suggested  anew 
by  Coze  and  are  furnished  with 
two  mouths  projecting  from  the  two  ends  of  the  furnace  (double-ended  or  "  through  " 
retorts).  When  these  are  inclined  at  an  angle  of  32°  and  are  charged  automatically 
from  above,  the  coal  distributes  itself  in  a  layer  of  uniform  depth  along  the  whole 
of  the  retort  (Fig.  49).  The  gas-discharge  tube  is  inserted  at  the  lower  mouth,  which 
at  the  end  of  the  operation  is  opened,  the  coke,  while  still  hot,  being  completely  and  immedi- 
ately discharged  into  an  iron  truck  or  on  to  a  moving  endless  perforated  band,  the  pieces 
of  coke  remaining  alight  being  sprinkled  with  water  before  being  discharged  on  to  the  coke 
ground.  Similar  retorts  are  used  with  elliptical  mouths;  the  upper  one  is  rather  larger 
(63  cm.  x  35  cm.)  than  the  lower  (57  cm.  x  30  cm.),  and  the  length  is  about  3-8  metres. 
At  the  present  day  they  vary  from  this  length  up  to  6  metres. 


42 


The  advantages  of  this  system  are  shown  by  the  following  results,  which  refer  to  three 
batteries  of  fourteen  (1)  inclined  and  (2)  horizontal  retorts  : 

Duration  of  the  distillation 

Charge  per  retort        ..... 

Number  of  charges  per  8  hours    . 

Total  coal  distilled  in  8  hours 

Cost  of  labour  per  1000  kilos  of  coal     . 

The  pressure  in  the  interior  of  the  retorts  should  be  carefully  regulated,  since,  if  it 
becomes  too  great,  escape  of  the  light  gases  and  vapours  readily  occurs  and  the  develop- 
ment of  vapours  and  gases  is  slackened,  the  hydrocarbons,  which  remain  for  a  long  time 
in  contact  with  the  red-hot  walls  of  the  retort,  undergoing  further  decomposition  with 
deposition  of  graphite  on  the  walls  and  liberation  of  hydrogen.  In  order  to  avoid  these 


Inclined. 

3  hours 
165  kilos 

Horizontal. 
4J  hours 
152  kilos 

112 

72 

18,500  kilos 
10  pence 

11,  000  kilos 
18  pence 

FIG.  48. 

inconveniences  the  retorts  are  to-day  put  in  indirect  communication  with  aspirators  or 
pressure  regulators  placed  beyond  the  washing  apparatus  (scrubbers,  etc.). 

The  layer  of  coal  in  the  retort  should  not  be  too  deep,  as  otherwise  the  gases  given  off 
are  decomposed  on  contact  with  the  upper  layers  of  hot  coke. 

With  the  view  of  avoiding  decomposition  of  the  more  luminous  gases,  which  are  evolved 
principally  at  the  beginning  of  the  distillation,  Bentrup  (1903)  proposed  passing  a  con- 
tinuous current  of  water-gas  (see  Vol.  I.,  pp.  365,  486)  into  the  retort  to  remove  these 
products  rapidly  from  contact  with  the  hot  walls  of  the  retort ;  the  water-gas  is  produced 
in  an  adjacent  retort  also  containing  red-hot  coke. 

As  often  happens  in  other  fields  of  work,  so  also  in  the  industries,  a  return  to  older 
methods  often  offers  advantages.  Thus  it  appears  at  the  present  time  that  the  vertical 
retorts  again  brought  into  use  by  Settle  and  Padfield  are  destined  to  supplant  the  inclined 
ones.  In  1905,  J.  Bueb  made  works  experiments  with  a  battery  of  ten  retorts,  4  metres 
in  length,  placed  vertically  in  a  furnace  and  provided  with  an  upper  aperture  for  charging 
and  a  lower  one  for  discharging  (that  is,  the  furnace  surrounds  only  the  external  vertical 
surface  of  the  retort,  which  is  heated  by  hot  gases  circulating  through  numerous  channels, 
as  shown  in  Fig.  50).  In  this  way  a  larger  charge  (up  to  500  kilos)  is  used,  the  luminous 
gases  are  not  decomposed  and  the  yield  of  gas  is  higher,  as  the  temperature  of  the  retort 


RETORTS 


43 


reaches  1300°  to  1400°  C. ;  at  the  same  time  very  little  naphthalene  is  produced,  the  incon- 
venience caused  by  depositions  of  naphthalene  in  the  cold  parts  of  the  pipes  being  thus 
avoided.  In  addition,  the  yield  of  ammonia  is  increased  by  35  per  cent.,  the  separation 
of  the  tar  is  facilitated,  and  the  cost  of  labour  diminished ;  a  less  amount  of  a  harder  coke 
is  obtained,  and  the  quantity  of  tar  is  considerably  decreased,  while  the  production  of 
gas  is  increased  (Ger.  Pat.  155,742).  Further,  the  tar  is  more  fluid  and  brown,  and  differs 
in  composition  from  ordinary  tar,  containing  only  2  to  4  per  cent,  of  free  carbon  in 
place  of  the  20  per  cent,  or  more  in  other  tar  (see  Tar),  and  also  only  one-half  as  much 
naphthalene. 

Fig.  50  shows  a  double  battery  of  Bueb  vertical  retorts,  4  metres  high  and  slightly 
conical  in  shape,  the  wider  mouth  at  the  bottom.  By  means  of  the  elevator,  A,  the  coal 
is  introduced  into  the  hopper  B  C,  whence  it  passes  into  the  movable  scoops,  D,  which 
carry  it  to  the  retorts.  At  the  end  of  the  distillation  (which  lasts  seven  to  eight  hours)  the 
coke  is  discharged  into  the  metal 
hopper  F,  and  thence  into  the 
channel,  G,  where  a  band  running 
on  rollers  carries  the  spent  coke  to 
the  store.  The  gas  issues  at  the 
top  of  the  retort,  and  by  the  tubes 
E  and  H  passes  into  the  hydraulic 
main,  /,  and  so  into  the  piping,  L ; 
the  tar  and  the  ammonia  liquors 
are  discharged  from  the  hydraulic 
main  into  the  tube  M ,  leading  to 
the  depositing  tank. 

In  order  to  increase  the  yield  of 
gas  by  10  to  15  per  cent,  it  has 
recently  been  proposed  to  utilise 
the  high  temperature  of  the  coke 
(1200°  to  1400°  C.)  remaining  in 
the  retorts  at  the  end  of  the 
distillation  to  produce  a  certain 
quantity  of  water-gas  by  passing  a 
current  of  steam  in  at  the  bottom 
of  the  retort  for  an  hour.  It  can- 
not, however,  be  denied  that  by 
this  wet  process  the  proportion  of 
carbon  monoxide  in  the  gas  is 
increased  (see  p.  58).  In  any  case 
total  yields  of  360  cu.  metres  of 
gas  per  1000  kilos  of  coal  have 
been  obtained  in  this  way. 

The  economy  in  labour  effected  by  this  retort  is  very  great,  and  it  is  calculated  that, 
whilst  with  horizontal  retorts  every  workman  produces  about  1600  cu.  metres  of  gas  per 
day,  with  the  vertical  retorts  the  amount  reaches  7000  cu.  metres. 

From  1906-1910  furnaces  with  507  batteries  of  5500  vertical  retorts,  representing  a 
total  daily  production  of  2,200,000  cu.  metres  of  gas,  have  been  manufactured  by  one  single 
firm  at  Dessau  (for  Berlin,  Cologne,  Zurich,  Trieste,  Genoa,  etc. ). 

In  the  working  of  these  vertical  retorts,  which  do  indeed  represent  a  marked  advance  on 
the  Coze  inclined  retort,  certain  disadvantages  have  been  observed,  the  coke  formed  being 
harder  than  the  ordinary  and  not  so  well  suited  for  domestic  purposes,  whilst  the  gas-dis- 
charge tubes  soon  become  obstructed  with  tarry  matters,  so  that  they  require  cleaning  every 
three  to  four  days ;  distillation  with  steam  during  the  last  phase  of  the  heating  relieves 
this  inconvenience  to  some  extent.  By  some  the  production  of  water-gas  as  described 
above  is  not  regarded  as  advantageous,  the  same  quantity  of  water-gas  being  obtainable 
more  economically  with  special  plant. 

A  further  and  more  recent  modification  consists  in  the  use  of  chamber  furnaces  (similar 
to  those  for  making  metallurgical  coke,  see  Vol.  I.,  p.  453). 

At  Munich  in  1908  and  at  Vienna  in  1909  inclined  chamber  furnaces  were  employed 


FIG.  49. 


44 


ORGANIC    CHEMISTRY 


(Kopper  system,  Fig.  51).  Coal  from  the  hopper,  2,  passes  down  an  inclined  plane  and 
fills  the  chamber,  5;  the  gas  is  led  into  the  trough,  1,  the  coke  is  discharged,  by  opening 
the  large  lower  door  with  a  crane,  4,  on  to  an  inclined  plane,  and  so  to  the  chain  transporter, 
6,  and  the  gas-producer,  8,  passes  the  gas  to  the  dust-chamber,  7,  and  then  to  the  ascension 
pipes  under  the  chambers ;  9  shows  another  battery  of  inclined  chambers.  With  chamber 


FIG.  50. 

furnaces  a  better  gas  is  obtained  with  a  less  expensive  plant  and  a  decided  economy  in 
labour,  the  daily  yield  of  gas  per  workman  reaching  9000  cu.  metres ;  the  coke  consumed  in 
the  producer  to  heat  the  furnaces  amounts  to  13  to  17  per  cent,  of  the  coal  distilled.  A 
plant  of  this  kind  was  finished  in  1910  at  Padua,  while  one  was  erected  in  1908  at  Munich 
and  another  in  1912  at  Vienna,  where  the  heating  of  the  chambers  is  effected  by  gas  from 
a  central  generator  with  a  revolving  hearth  (see  Vol.  I.,  p.  491). 


PURIFICATION     OF    GAS 


45 


With  horizontal  or  inclined  retorts  the  coal  is  heated  for  four  to  six  hours ;  with  vertical 
ones,  twelve  hours ;  and  with  chamber  furnaces,  twenty-four  hours. 

FURNACES.  Retorts  were  first  of  all  heated  by  direct  flame,  but  in  this  way  the 
heat  is  inefficiently  utilised ;  then  indirect  heating  by  flues,  just  as  for  steam  boilers,  was 
tried,  but  the  nearer  retorts  wore  out  very  rapidly,  so  that  later  several  retorts  were  placed 
in  one  furnace  in  direct  contact  with  the  hot  gases,  these  being  so  interrupted  and  deviated 
that  the  surfaces  of  all  the  retorts  were  uniformly  heated  (Fig.  48). 

At  the  present  time  the  use  of  the  regenerator  gas  furnace  (gas-producers,  see  Vol.  I., 
pp.  487,  634)  has  become  general,  coke  (usually  waste)  being  employed,  and,  in  countries 
where  there  is  little  demand  for  tar,  the  latter  being  used  as  fuel  by  injection  into  suitable 
furnaces.  The  coke  used  to  heat  the  furnaces  represents  about  25  per  cent,  or  30  per  cent, 
of  the  total  amount  produced.  In  some  works  (e.  g.,  at  Turin  since  1909)  the  heating  of 
the  furnaces  is  profitably  effected  by  9  to  10  per  cent,  of  tar  (on  the  weight  of  coal  distilled), 
burnt  in  special  gas-producers  with  recovery  of  the  heat.1 

The  wear  of  the  furnaces  and  retorts  is  considerable,  and  their  cost  is  calculated  as 
annual  expenditure  rather  than  as  cost  of  plant,  since  they  are  sometimes  remade  or 
renovated  twice  a  year. 

PURIFICATION  OF  GAS.  The  crude  products  obtained  directly  from  the  carbonisa- 
tion of  bituminous  coal  cannot  be  used  immediately  for  lighting  and  other  purposes.  The 


FIG.  51. 

gas  issues  from  the  retorts  at  very  high  temperatures  (up  to  250°),  and  it  is  evident  that, 
as  it  gradually  cools,  various  products  separate,  first  of  all  those  which  are  solid  or  liquid 
at  ordinary  temperatures.  It  is  necessary  to  remove  the  tar,  naphthalene,  ammonia 
liquor,  and  the  cyanogen  and  sulphur  compounds  by  means  of  the  following  apparatus. 

HYDRAULIC  MAIN.  This  is  a  wide  circular  or  semi-circular  pipe  (diameter,  30  to 
60  cm.)  of  sheet-iron  or  cast-iron  (Fig.  48,  V),  containing  water  and  tar,  and  placed  above 
the  retorts  so  that  the  ascension  pipes,  R  (12  to  18  cm.  in  diameter),  from  one  battery 
of  retorts  dip  into  it,  these  pipes  starting  from  the  lower  parts  of  the  retorts  and  carrying 
off  all  the  hot  gas  developed.  The  pipes,  E,  are  sealed  hydraulically  by  dipping  into  water 
in  the  hydraulic  main,  in  which  most  of  the  tar  and  the  part  of  the  ammoniacal  liquor 
containing  the  ammonium  sulphate,  chloride,  and  thiocyanate  condense,  while  the  ammonium 
carbonate  and  sulphide  condense  in  the  "  Standard "  (see  below).  The  hydraulic  main 
falls  slightly  towards  one  end,  so  as  to  facilitate  flow  of  the  tar  to  the  store-tanks,  in  which  it 

1  The  thermal  balance  for  the  distillation  of  coal  is  established  from  the  following  data  :  the 
formation  of  coke  is  more  or  less  endothermic  according  to  the  higher  or  lower  content  of  oxygen 
and  volatile  products ;  with  less  than  3  per  cent,  of  oxygen  the  endothermic  effect  is  almost  zero, 
and  with  7  to  8  per  cent.,  250  Cals.  per  kilo  of  coal.  The  distillation  of  such  a  coal  in  retorts 
absorbs  257  Cals.,  the  hot  gases  and  vapours  evolved  carry  away  180  Cals.,  and  the  heat  remaining 
in  the  hot  coke  is  246  Cals.,  the  total  for  the  retorts  alone  being  683  Cals.  Allowing  for  the  heat 
radiated  from  the  furnaces  and  that  lost  in  the  gases  and  ash,  the  total  endothermic  effect  amounts 
to  1047  Cals.  If  the  heat  of  the  furnace  gases  is  recovered  to  heat  the  air  for  burning  the  gas  from 
the  gas-producers,  the  22  per  cent,  of  coal  (calculated  on  that  distilled)  consumed  in  the  gas- 
producers  becomes  reduced  to  10-2  per  cent.  Good  furnaces  are  those  of  the  Woodall-Duckham 
and  Glover- West  types  with  continuous  working. 


46 


ORGANIC    CHEMISTRY 


gradually  becomes  almost  entirely  separated  from  the  ammonia  liquors,  being  sold  to  the 
tar-distiller  with  a  content  of  not  more  than  5  per  cent,  of  water  at  a  price  of  about  seventeen 
pence  per  cwt.  (3'50  lire  per  quintal ). 

The  still  very  impure  gas,  holding  in  suspension -large  numbers  of  tar  drops — which 
render  difficult  the  condensation  of  the  naphthalene — and  having  a  temperature  of  60°  to 
100°  C.,  is  gradually  cooled  to  12°  to  15°  C.  by  causing  it  to  traverse  a  large  iron  pipe  passing 
round  inside  the  whole  of  the  works  and  cooled  by  the  air ;  the  gas  then  reaches  a  condenser, 
formed  either  of  a  battery  of  tall  iron  tubes  (Fig.  52)  sprayed  outside  with  water,  or  of  a 
series  of  three  or  four  double- jacketed  cylinders,  5  to  6  metres  high,  cooled  inside  and  outside 
by  the  air,  the  gas  passing  into  the  jacket  (Fig.  53);  or  the  gas  may  be  circulated  round  a 
number  of  narrow  tubes  through  which  passes  a  continuous  stream  of  cold  water  (Fig.  54). 
The  cooling  thus  effected  is  gradual,  and  the  separation  of  the  naphthalene  and  tar  is 

more  complete,  while  there  is  no  danger  of  stoppages 
from  the  naphthalene ;  in  winter  the  gas  enters  the 
cooler  at  50°  to  60°  C.  and  leaves  at  5°  to  10°  C., 
while  in  summer  it  enters  at  60°  to  70°  C.  and 
emerges  at  30°  to  35°  C.  At  the  bottom  of  these 
tubes  is  found  a  deposit  of  tar — which  is  discharged 


FIG.  52. 


I 
Fio.  53. 


) 


FIG.  54. 


into  tanks — and  of  ammonia  liquors  at  7°  to  8°  Be.  The  consumption  of  water  in 
these  coolers  is  from  3  to  4  cu.  metres  per  twenty-four  hours  per  1000  cu.  metres 
of  gas. 

If  an  obstruction  of  naphthalene  occurs  at  any  point,  the  pressure— indicated  by 
manometers  placed  along  the  tubes — shows  an  increase  at  that  point. 

The  gas  issuing  from  the  condensers  still  contains  suspended  tar,  which  it  is  necessary 
to  separate.  To  this  end  serves  Audouin  and  Pelouze's  tar-separator,  shown  in  Fig.  55. 
The  gas  passes  along  the  tube  B,  which  opens  into  a  perforated  double- walled  bell,  D,  the 
pressure  in  which  is  regulated  by  a  compensating  weight  and  pulley,  0.  The  bell  is  partially 
sealed  hydraulically  and  rises  more  or  less,  leaving  open  a  greater  or  less  number  of  apertures, 
according  to  the  pressure  of  the  gas.  The  gas  is  thus  subjected  to  a  kind  of  filtration 
through  small  orifices,  the  fine  drops  of  tar  being  condensed  into  larger  drops,  which  separate 
and  collect  in  E,  whence  the  excess  is  run  off  at  F.  The  gas  thus  purified  from  tar  passes 
by  the  tube  C  to  the  ammonia-condensing  apparatus.  The  tar-separator  should  not  be 
kept  too  cold  (12°  to  15°'  C.). 

NAPHTHALENE  SEPARATORS.  Naphthalene  is  a  product  of  the  condensation 
by  heat  of  the  heavy  hydrocarbons  of  the  gas.  It  is  difficult  to  imagine  how  pertinaciously 
gas  carries  through  all  the  purifying  operations  considerable  quantities  of  naphthalene 
suspended  in  it,  and  how  slowly  this  naphthalene  is  deposited  in  town  mains,  ultimately 


SEPARATION     OF    AMMONIA 


47 


stopping    them    and    causing    great    inconvenience    and    expense    to    consumers    and 
manufacturers. 

In  1899  Bueb,  on  the  basis  of  former  experiments  of  Young  and  Glover,  succeeded  in 
avoiding  this  trouble  to  a  great  extent  by  passing  the  gas  (first  .washed  with  water  in  the 
"  Standard  "  washer-scrubber  to  separate  the  ammonia)  into  a  drum  similar  to  the  "  Stand- 
ard "  (see  below),  but  with  three  independent  chambers  in  which  the  gas  is  washed  with 
anthracene  oil  of  medium  density  (prepared  by  the  distillation  of  tar  and  having  the  b.-pt. 
350°  to  400°  C.  ),1  which  dissolves  and  fixes  almost  all  the  naphthalene.  When  the  oil  of 
the  first  chamber  is  saturated  it  is  removed,  and  that  of  the  second  chamber  passes  into  the 
first  and  that  of  the  third  into  the  second;  the  third  chamber  is  charged  with  fresh  oil, 
containing  4  per  cent,  of  benzene  in  order  to  avoid  loss  of  light-giving  products  from  the  gas. 
The  anthracene  oil,  saturated  with  naphthalene  (23  per  cent.)  may  be  utilised  as  such,  or 
mixed  with  ordinary  tar.  Less  than  5  grams  of  naphthalene  per  100  cu.  metres  remains 
in  the  washed  gas. 


FIG.  55. 


FIG.  56. 


According  to  U.S.  Pat.  968,509  of  1910,  naphthalene  may  be  separated  by  bubbling 
the  gas  through  an  aqueous  solution  of  picric  acid,  this  giving  rise  to  an  insoluble  naphtha- 
lene picrate,  from  which  the  naphthalene  may  be  distilled  by  means  of  steam,  the  picric 
acid  being  left. 

SEPARATION  OF  AMMONIA.2    The  washing  of  the  gas  for  the  purpose  of  removing 

1  It  seems  that,  when  a  lighter  tar  oil  (sp.  gr.  less  than  1)  is  used  in  the  proportion  of  3-76 
grams  per  cubic  metre  of  gas,  as  much  as  0-951  gram  of  naphthalene  can  be  fixed,  whereas  the 
heavy  oil  fixes  only  0-2  gram ;   in  the  former  case  as  little  as  2  grams  of  naphthalene  per  100 
cu.  metres  has  been  left  in  the  gas. 

2  Of  the  nitrogen  present  in  coal  (1  to  2  per  cent.),  about  one-half  remains  in  the  coke,  2  to  3 
per  cent,  yields  cyanides  and  hydrocyanic  acid,  and  about  20  per  cent,  occurs  free,  and  10  to  15 
per  cent,  as  free  and  combined  ammonia  (ammonium  sulphide,  carbonate  and  chloride)  in  the 
gas.     It  has  been  shown  that  the  proportion  of  nitrogen  transformed  into  ammonia  is   much 
greater  than  that  found  in  this  form  in  the  gas,  as  more  or  less  of  the  ammonia  undergoes  dissocia- 
tion into  nitrogen  and  hydrogen  (especially  above  800°).     The  extent  of  this,  dissociation  depends 
on  the  nature  of  the  ash  of  the  coal  (iron  and  its  oxide  act  as  dissociating  catalysts  in  the  hot)  and 
on  the  temperature  of  the  walls  of  the  retort  and  of  the  coke.     Thus,  in  horizontal  retorts,  where 
the  gas  remains  more  readily  in  contact  with  the  upper  walls,  which  form  a  heated  arch,  the 
ammonia  is  more  highly  dissociated  than  in  vertical  retorts  and  in  chamber  furnaces,  where  the 
gas  is  in  contact  more  with  the  central  mass  of  the  coal  than  with  the  retort  walls. 


48 


ORGANIC    CHEMISTRY 


the  ammonia  may  be  effected  by  ordinary  water,  which  has  a  great  affinity  for  ammonia, 
or  by  the  dilute  ammonia  liquor  from  the  hydraulic-main  (1°  to  2°  Be.),  but  not  with 
that  from  the  condenser,  which  is  too  concentrated  (7°  to  8°  Be.).  The  most  common 
form  of  apparatus  used  for  this  washing  is  the  scrubber  or,  better  still,  the  "  Standard  " 
washer-scrubber. 

SCRUBBERS  are  usually  formed  of  a  series  of  coke-towers  through  which  water  trickles 
(Fig.  56).  The  gas  that  enters  the  bottom  of  the  first  tower  is  washed  with  dilute  ammonia, 
condensed  in  succeeding  towers,  and  when  it  reaches  the  last  tower  it  is  washed  with  pure 
water,  which  dissolves  the  last  traces  of  ammonia  and  may  be  used  subsequently  for  the 
first  tower,  from  the  bottom  of  which  it  is  carried  off,  rich  in  ammonia,  by  small  syphons. 
These  towers,  which  are  of  cast-iron  sheets,  are  joined  in  twos  or  threes  in  such  a  way  that 
the  gas  is  conducted  from  the  top  of  the  first  tower  to  the  bottom  of  the  second,  and  so  on. 
The  interior  may  be  fitted  simply  with  water  pulverisers,  or  it  may  be  filled  with  coke, 
chips  of  wood,  broken  bricks,  or,  what  are  more  efficient,  vertical  bundles  of  sticks,  or  of 
corrugated  and  toothed  iron  sheets. 

Scrubbers  are  1  to  3  metres  in  diameter  and  4  to  20  metres  in  height.  A  maximum 
production  of  1000  cu.  metres  of  gas  per  twenty-four  hours  requires  5  to  6  cu.  metres  of 
scrubber,  the  gas  taking  eight  to  ten  minutes  to  pass  through.  Before  entering  the  scrubber 
the  gas  contains  200  to  400  grams  of  ammonia  per  100  cu.  metres,  whilst  afterwards 
this  volume  contains  only  1  to  10  grams. 


FIG.  57. 


FIG.  58. 


The  "  STANDARD  "  washer- scrubber  consists  of  a  large  horizontal  fixed  cylinder  of 
iron- plate,  divided  by  septa  normal  to  the  axis  into  seven  chambers  (Fig.  57 ).  This  cylinder 
is  traversed  by  a  rotatable  axis  carrying  seven  paddles  of  almost  the  same  diameter  as  the 
chambers  and  each  consisting  of  two  large  metal  plates  to  which  are  fixed  the  ends  of  super- 
posed wooden  laths  with  spaces,  not  exactly  superposed,  between  (Fig.  58).  These  paddles 
rotate  with  the  axis  and  dip  into  water  which  fills  the  chambers  to  about  one-third  of  the 
height  of  the  cylinder.  The  pure  water  enters  chamber  VII  at  a  and  passes  from  chamber  to 
chamber  until  it  reaches  the  first,  the  walls  separating  the  chambers  being  successively 
lower.  The  gas  to  be  purified  moves  in  the  opposite  direction,  entering  chamber  I,  and 
passing  between  all  the  laths  of  the  paddle  from  the  centre  to  the  periphery,  then  descending 
to  the  centre  of  the  next  paddle  in  chamber  II,  as  shown  by  the  arrows,  4  and  5,  again  issuing 
at  the  periphery,  passing  into  chamber  III,  and  so  on.  In  this  way  the  gas  is  perfectly 
washed  and  loses  also  part  of  its  CO2  and  H2S.  The  water  leaves  chamber  I  with  a  density 
of  7°  to  8°  Be. 

At  Munich  the  ammonia  is  eliminated  in  the  dry  way  by  passing  the  gas  over  super- 
phosphate, which  fixes  it  and  then  serves  as  an  excellent  fertiliser  (with  7  to  8  per  cent,  of 
nitrogen) :  1000  kilos  of  superphosphate  are  sufficient  to  purify  32,000  cu.  metres  of  gas 
(with  3  per  cent,  of  NH3),  the  small  quantity  of  thiocyanate  (0-5  to  2-5  per  cent.)  which  it 
contains  having  no  injurious  action  on  plants.  N.  Caro  (U.S.  Pat.  952,560,  March  22, 
1910)  cools  the  gas  from  coke  manufacture  to  20°  and»then  passes  it  through  a  solution 
of  ammonium  sulphate  of  29°  to  36°  Be.  containing  5  per  cent,  of  free  sulphuric  acid ; 


REMOVAL     OF     SULPHUR  49 

ammonium  sulphate  gradually  crystallises  out  and  the  gas  passes  off  free  from  ammonia. 
Generally,  however,  ammoniacal  liquors  are  distilled  with  lime  and  the  ammonia  fixed 
with  sulphuric  acid  (see  Vol.  I.,  p.  358).  Every  ton  of  coal  carbonised  yields  10  to  12  kilos 
of  commercial  ammonium  sulphate. 

For  some  years  increasing  use  has  been  made  of  the  method  of  fixing  the  ammonia 
of  lighting  gas  by  means  of  concentrated  sulphuric  acid  so  as  to  obtain  directly  crystallised 
ammonium  sulphate,  as  was  suggested  by  Mallet  in  1840,  by  Laming  in  1852,  and  by  Brun 
in  1903,  the  acid  being  previously  heated  to  80°  to  85°  so  that  the  moisture  is  not  condensed 
and  the  acid  not  increased  in  volume.  The  tar  could  not,  however,  be  completely  eliminated 
beforehand  from  the  hot  gas;  better  results  in  this  direction  were  obtained  in  1905  by 
centrifuging  the  gas,  and  in  1906  Otto  expelled  the  tar  by  passing  the  gas  into  towers  or 
cylinders  in  which  tar  was  pulverised  at  the  top.  When  the  hot  gas  is  treated,  this  is 
taken  as  it  issues  from  the  hydraulic  main,  the  shallow  layer  of  tar  which  always  separates 
at  the  surface  of  the  acid  in  the  neutraliser  being  run  off  by  a  pipe ;  the  crystalline  sulphate 
which  separates  is  extracted  continuously  by  means  of  suitable  ejectors  (see  also  Fr.  Pat. 
418,018).  In  order  that  water  may  not  condense  in  the  pipes  before  the  neutralising  vessel, 
the  gas  must  be  kept  at  about  80°  (gas  from  coke-ovens  contains  up  to  145  grams  of  water 
vapour  per  cubic  metre,  and  in  this  case  the  temperature  of  hygrometric  saturation  is  80-7°) ; 
the  tar  separator  must  also  be  warm,  in  order  that  water  may  not  condense  therein.  The 
crude  gas  may  contain  10  to  12  grams  of  ammonia  per  cubic  metre,  and  the  heat  of  reaction 
with  sulphuric  acid  suffices  to  maintain  the  temperature  of  the  acid  and  gas ;  the  heat  of 
reaction  is  greater  for  the  ammonia  existing  as  salts.  If  less  than  the  above  proportion  of 
ammonia  is  present  and  the  gas  is  saturated  with  moisture,  the  heat  of  reaction  is  insufficient 
and  the  acid  must  be  heated.  Less  convenient  is  the  Koppers'  system,  according  to  which 
the  gas  is  cooled  to  30°  to  separate  the  tar  and  then  heated  by  a  counter- current  of  the 
hot  furnace  gases,  the  ammonia  water  condensing  at  30°  being  heated  separately  to  expel 
the  ammonia  which  is  introduced  into  the  gas  before  the  latter  reaches  the  neutralising 
vessel. 

SEPARATION  OF  THE  SULPHUR  COMPOUNDS  AND  CYANOGEN  COM- 
POUNDS. The  volatile  or  organic  sulphur  of  the  coal  (0-4  to  0-8  per  cent.  S. )  occurs  to 
the  extent  of  about  one-half  in  the  impure  gas,  97  per  cent,  of  it  as  H2S  and  sulphides  and 
the  rest  as  CS2  and  other  aliphatic  and  aromatic  sulphur  compounds  (see  above).  The 
fixed  sulphur  of  the  sulphates  and  pyrites  remains  in  the  coke. 

After  the  ammonia,  the  following  gases  must  be  removed  :  H2S,  COS,  C02,  HCN,  CS2, 
thiocyanates,  sulphur  derivatives  of  hydrocarbons,  etc.  This  is  especially  important  with 
H2S  and  other  sulphur  compounds  (about  1  to  1-5  per  cent,  by  volume  of  the  crude  gas), 
since  they  partly  burn,  forming  SO2,  and  partly  escape  unaltered  from  the  gas-jets,  decora- 
tions, metal-work,  and  paintings  being  discoloured ;  also  the  poisonous  properties  of  these 
compounds  are  considerable,  the  crude  gas  containing  0-1  to  0-25  per  cent,  by  volume  of 
hydrocyanic"acid.  The  test  employed  by  large  consumers  to  detect  hydrogen  sulphide  is 
very  rigorous,  and  is  made  with  lead  acetate  paper,  which  blackens  on  prolonged  exposure 
to  impure  gas. 

The  final  purification  of  gas  has  been  in  use  ever  since  the  beginning  of  the  industry. 
In  1806  Clegg  purified  gas  partially  by  passing  it  through  milk  of  lime,  but  such  large 
volumes  of  liquid  were  required  that  their  preparation  was  difficult,  while  the  purification 
effected  was  not  complete.  He  then  proposed  the  use  of  powdered  slaked  lime,  which  fixes 
carbon  dioxide,  as  well  as  many  sulphur  compounds,  forming  calcium  sulphydroxide, 
OH-Ca-SH ;  but  if  much  CO2  is  present  the  sulphydroxide  is  decomposed  and  SH2  regener- 
ated. In  1840  Mallet  suggested  the  use  of  manganese  oxide,  which  fixes  H2S  more  readily, 
but  this  method  did  not  give  good  results.1 

1  In  1847  Laming  succeeded  in  purifying  gas  well  and  easily  by  means  of  a  mixture  of  160 
parts  of  lime,  180  of  sawdust,  and  30  of  ferrous  sulphate  dissolved  in  scarcely  sufficient  water  to 
moisten  the  mass ;  it  is  kept  turned  over  for  some  days  in  the  air,  until  it  becomes  brown  owing 
to  the  conversion  of  the. ferrous  sulphate  into  ferrous  hydroxide  and  then  ferric  hydroxide.  The 
latter,  in  the  moist  state,  is  capable  of  fixing  rapidly  the  hydrogen  sulphide  and  the  sulphides 
(see  p.  50 ),  while  part  of  the  carbon  dioxide  is  fixed  by  the  excess  of  lime.  The  use  of  Laming 
mixture  spread  quickly  to  almost  all  gas-works,  and  only  subsequent  to  1890  was  it  replaced 
gradually  by  natural  hydrated  ferric  oxide  (see  p.  50). 

In  1868  F.  C.  Hills  attempted  to  separate  the  sulphur  compounds  of  the  gas  and  those  occur- 
ring in  the  ammonia  water  (especially  as  ammonium  sulphide  and  carbonate)  by  washing  the 
gas  with  this  water  heated  to  90°,  since  at  this  temperature  thcte  substances  dissociate,  the 
VOL.  II.  4 


50 


ORGANIC    CHEMISTRY 


Nowadays  the  dry  purification  of  lighting  gas  is  effected  almost  everywhere  by  means 
of  natural  hydrated  ferric  oxide  (Fe203  +  2Fe(OH)3)  in  the  form  of  the  porous,  yellowish- 
brown  earth,  limonite,  which  is  mixed  with  a  little  lime  and  sawdust  to  render  the  reaction 
less  violent.  The  ferric  hydroxide  fixes  the  hydrogen  sulphide  and  other  sulphides : 
2Fe(OH)3  +  3H2S  =  6H20  +  Fe-jS^iron  sesquisulphide  or  2FeS  +  S)  with  development 
of  heat,  and  also  forms  iron  cyanide  or  thiocyanate  with  the  hydrocyanic  acid,  i.  e.,  with 
the  ammonium  cyanide  and  thiocyanates. 

The  whole  of  the  iron  present  does  not  take  part  in  these  reactions,  but  when  the  mixture 
is  exhausted  it  may  be  regenerated  by  exposure  and  turning  in  the  air  for  two  or  three  days, 
the  whole  of  the  sulphur  being  liberated  : 

Fe2S3  +  30  +  3H2(f=  2Fe(OH)3  +  3S. 

The  mass  may  be  thus  revivified  and  used  again  some  ten  or  more  times,  after  which 
it  is  rejected.  This  product  contains  35  to  50  per  cent,  of  free  sulphur,  10  to  15  per  cent, 
of  Prussian  blue,  1  to  4  per  cent,  of  ammonium  thiocyanate,  and  1  to  4  per  cent,  of  am- 
monium sulphate,  and  nowadays  the  free  sulphur  is  often  extracted  by  carbon  disulphide, 
while  from  the  residue  cyanides  and  ferrocyanides  may  be  obtained;  or  the  mass  is  first 
extracted  with  water  to  obtain  the  cyanides  and  the  ammonium  sulphate,  the  dried  residue 
being  used  in  place  of  pyrites  in  the  manufacture  of  sulphuric  acid  (see  Vol.  I.,  pp.  291, 
840).1 


|y 

TS 

LI 

FIG.  59. 


FIG.  60. 


These  mixtures  give  good  results  and  are  placed  on  the  market  under  various  names : 
Deicke  mixture  with  66  per  cent.  Fe203  and  Lux  mixture  with  51  per  cent.  Fe203.  They 
are  made  by  mixing  the  powdered  iron  residues  from  the  working  of  bauxite  with  soda 
and  fusing  in  a  furnace,  the  silicates  which  have  become  soluble  being  then  extracted  by 
water  and  the  remaining  ferric  hydroxide  mixed  with  double  its  volume  of  sawdust :  1  cu. 
metre  of  this  "  Lux  "  mixture,  at  an  initial  cost  at  the  Ludwigshafen  factory  of  about 
15s.  per  ton,  purifies  more  than  10,000  cu.  metres  of  gas,  whilst  natural  Silesian  ferric  oxide 
costs  8s.  to  12s.  per  ton. 

The  purifying  mixture  is  arranged  in  several  layers,  all  of  which  are  traversed  by  the 
gas  (Fig.  59).  The  cover  to  the  chamber  is  water-sealed  (Fig.  60),  and  may  easily  be  raised 
by  means  of  a  crane  when  the  mass  is  to  b6  removed  for  regeneration.  It  is  simpler  to 

H2S  and  C02  being  liberated  and  the  more  soluble  ammonia  retained ;  actually,  however,  a  large 
part  of  the  ammonia  is  lost,  and  the  process  was  abandoned.  C.  F.  Glaus  (1884-1892)  applied 
on  a  large  scale  at  Belfast  the  purification  of  gas  from  sulphur  compounds  by  using  gaseous 
ammonia  instead  of  aqueous  ammonia  in  a  complex  system  of  scrubbers,  pumps,  heaters,  etc., 
the  sulphur  of  the  hydrogen  sulphide  being  recovered  in  the  same  way  as  from  Leblanc  soda 
residues  (see  Vol.  I.,  p.  596);  the  process  failed  in  practice  and  was  discarded. 

1  The  cyanogen  compounds  of  the  crude  gas  which  are  formed  from  ammonia  by  the  action 
of  heat  and  cause  corrosion  of  ironwork  are  best  separated  in  the  wet  way  by  Bueb's  process 
(Vol.  L,  p.  840).  This  process  has  given  satisfactory  results  in  the  Turin  gasworks  and  many 
others  in  Europe,  but  is  already  beginning  to  lose  its  importance,  owing  to  the  discovery  of  new 
synthetical  methods  of  preparing  potassium  cyanide  (Vol.  I.,  p.  548). 


REMOVAL    OF     SULPHUR 


51 


use  a  single  layer  of  the  mass  50  to  60  cm.  deep,  the  gas  being  introduced  at  a  greater 
pressure;  it  is  then  easier  to  discharge  the  exhausted  mass  through  an  aperture  in  the 
base  of  the  reservoir.1  At  the  present  day  the  costly  labour  required  for  the  regeneration 
is  avoided  by  not  emptying  the  reservoir,  the  mass  being  kept  always  oxidised  by  mixing 
about  1-5  to  2  per  cent,  of  air  with  the  gas  before  passing  it  into  the  chamber;  with  more 
air  the  mass  heats  too  much. 

Many  years  ago  W.  Feld  attacked  the  problem  of  separating  the  sulphur  compounds 
from  gas.  In  his  first  attempts  he  utilised  the  ready  absorption  of  H2S  by  zinc  thiosulphate, 
with  separation  of  S  and  ZnS,  the  latter  being  afterwards  converted  into  the  thiosulphate 
by  means  of  SO2 :  (a)  ZnS2O3  +  3H2S  =  ZnS  +  4S  +  3H20;  (b)  2ZnS  +  3S02  =  S  + 
2ZnS203.  A  plant  erected  at  the  works  of  the  East  Hull  Gas  Company  in  1909  did  not 
give  satisfactory  results,  and  was  abandoned  in  1910,  the  conversion  of  zinc  sulphide  into 
the  thiosulphate  being  difficult;  further,  the  regenerated  solution  absorbs  the  H2S  less 
completely  (only  30  to  40  per  cent.),  zinc  sulphate  being  formed. 

In  the  second  stage  of  his  attempts  Feld  used  iron  thiosulphate,  which  not  only  fixes 
the  H2S  more  easily,  but  also  completely  fixes  the  ammonia,  with  formation  of  FeS  (this 
with  S02  gives  the  thiosulphate  again)  and  ammonium  thiosulphate;  the  latter,  with  iron 
thiosulphate  and  SO2,  yields  iron  and  ammonium  polythiosulphates  :  (c)  FeS2O3  +  H2S  + 


2NH3  =  FeS  +  (NH4)2S2O3;  (d)  2FeS  +  3S02  =  S  +  2FeS2O3;  (e)  FeS203  +  (NH4)2 
S2O3  +  3SO2  =  FeS3O6  +  (NH4)2S406.  In  the  hot  these  polythionates  decompose  thus  : 
(/)  FeS306  +  (NH4)2S4O6  =  3S  +  FeS04  +  2SO2  +  (NH4)2S04.  The  final  mass  thus 
obtained  is  also  capable  of  fixing  ammonia  and  H2S,  with  separation  of  ammonium  sulphate  : 
(g)  FeSO4  +  2(NH4)2S04  +  2NH3  +  H2S  =  FeS  +  3(NH4)2SO4;  with  S02,  the  ferrous 
sulphide  yields  the  thiosulphate  (d)  again. 

This  second  process  of  Feld  was  tried  in  the  municipal  works  at  Koenigsberg,  the  results 
being  moderately  satisfactory,  especially  if  the  gas  is  hot.  Feld  then  found  that  ammonium 
polythionate  (formed  from  the  thionate  and  S02,  see  reaction  e)  suffices  to  fix  both  the 
ammonia  and  the  hydrogen  sulphide:  (h)  (NH4)2S4O9  +  3H2S  ==  (NH4)2S203  +  5S  + 
3H20;  (»)  (NH4)2S406  +  2NH3  +  H2O  =  S  +  (NH4)2S2O3  +  (NH4)2S04,  and,  in  the 
hot,  (k)  (NH4)2S4O6  =  (NH4)2S04  +  SO2  +  2S.  The  sulphur  separating  is  transformed 
into  SO2  by  burning  it  with  air,  so  that  all  the  ammonia  and  sulphur  of  the  gas  are 
converted  into  ammonium  sulphate  without  using  sulphuric  acid.  The  ammonium  poly- 
thionate solution  is  obtained  at  the  beginning  of  the  process  from  the  gas  itself,  which 

1  This  exhausted  mass  is  often  utilised  for  the  sulphur  it  contains,  while  in  many  other  cases 
the  cyanides,  thiocyanates,  ferrocyanides,  etc.,  are  extracted  (see  Vol.  I.,  p.  841);  it  is  also 
sometimes  used  on  roads  as  a  weed-killer — cyanides  having  a  poisonous  action  on  plants — 
and,  finally,  it  has  been  proposed  as  a  nitrogenous  fertiliser  (it  contains  on  the  average  5  to  6 
per  cent,  of  nitrogen,  one-tenth  of  which  is  in  the  form  of  ammonia  and  the  rest  as  cyanide), 
but  it  must  be  spread  on  the  naked  soil  two  or  three  months  before  sowing  takes  place,  as  it 
takes  time  to  decompose  and  become  innocuous  to  vegetation. 


52  ORGANIC    CHEMISTRY 

contains  ammonium  sulphide  (after  the  Pelouze  tar  separators),  by  passing  it  into  the 
Feld  centrifugal  washer  (see  below)  together  with  SO2 :  2(NH4)2S  +  6SO2  =  2(NH4)2S4O6. 
The  Koenigsberg  plant  is  shown  diagramrnatically.  in  Fig.  61.  The  ammonium  polythionate 
solution  is  pumped  by  the  pump  /  from  the  vat  C  to  the  upper  part  of  the  Feld  centrifugal 
washer  A,  the  mouth  b  at  the  lower  part  admitting  the  gas  which  issues  purified  from  the 
upper  orifice  c.  When  the  polythionate  is  converted  into  thionate  according  to  equations 
h  and  i,  it  is  discharged  into  a  small  Feld  washer  B,  where  it  meets  a  current  of  hot  SO2 
from  the  sulphur  burner  S,  and  collects  in  the  regenerating  vat  C,  in  which  the  conversion 
into  polythionate  is  completed.  This  passes  into  circulation  again  until  it  becomes  enriched 
with  35  to  40  per  cent,  of  ammonium  sulphate,  part  of  the  solution  then  going  through 
the  tap  e  to  the  boiler  D,  where  it  is  heated  with  steam  at  100°  for  five  to  six  hours  in  order 
to  transform  the  polythionate  into  ammonium  sulphate  with  separation  of  sulphur  and 
formation  of  SO2  (see  reaction  k),  the  latter  being  conducted  into  B.  The  boiler  is  then 
discharged  into  the  centrifuge  E,  which  retains  the  sulphur,  whilst  the  hot  ammonium 
sulphate  solution  collects  in  the  vat  G,  whence  it  is  delivered  into  the  vacuum  evaporator 
H ;  from  this  the  ammonium  sulphate  is  discharged,  as  it  separates,  into  the  centrifuge  7, 
the  vacuum  in  the  evaporator  being  maintained  meanwhile  by  the  pump  K.1 

At  Koenigsberg  40,000  cu.  metres  of  gas  are  purified  per  twenty-four  hours,  with  pro- 
duction of  400  kilos  of  sulphur,  which  is  burnt.  The  absorption  of  the  ammonia  is  com- 
plete, independently  of  the  temperature  of  the  gas  and  air,  whilst  that  of  the  hydrogen 
sulphide,  although  not  complete,  is  good.  Whereas  in  1910,  with  the  old  plant,  5-5  kilos 
of  ammonium  sulphate  were  obtained  per  ton  of  coal  gasified,  in  1912,  by  means  of  the 
Feld  process,  10-2  kilos  were  obtained.  After  the  final  improvements  had  been  made  in 
the  process,  the  municipality  of  Koenigsberg  decided  in  1913  to  apply  it  to  their  whole 
output  of  gas,  the  old  cumbersome  purifiers  being  abandoned.  The  success  of  this  process 
is  due  largely  to  the  excellent  results  furnished  by  the  Feld  centrifugal  washer,  which  may 
be  applied  in  other  industries  where  gases  containing  dust  are  to  be  washed  or  where  gases, 
mixed  and  diluted  with  other  insoluble  gases,  are  to  be  dissolved  and  fixed. 

This  Feld  washer  (Fig.  62),  patented  in  1905,  consists  of  five  or  more  superposed  cast- 
iron  rings  forming  a  tower  divided  into  as  many  chambers  communicating  with  one  another 
by  means  of  apertures,  a,  in  the  plates  separating  the  chambers.  A  central  shaft,  rotated 
rapidly  by  the  gearing  C,  is  fitted  in  each  chamber  with  a  cast-iron  cross-piece,  6,  to  which 
are  fixed  four  concentric  cones  of  5  mm.  sheet-iron,  open  at  the  base  and  with  the  smaller 
aperture  at  the  bottom.  These  cones  are  28  mm.  apart,  the  external  peripheral  cone  being 
somewhat  higher,  and  perforated  all  round  for  a  height  of  18  cm.  with  orifices  5x12  mm. 
When  the  shaft  and  cones  rotate,  the  liquid  of  the  basin  into  which  they  dip  is  drawn  up 
between  the  cones  and  forced  out  of  the  mouth  at  the  top,  forming  a  disc  of  liquid  having 
the  diameter  of  the  apparatus ;  the  liquid  projected  against  the  walls  falls  to  the  bottom, 

1  Returning  to  the  Hills  and  Glaus  process  (see  above)  Burkheis-'er  filed  a  series  of  patents 
(Ger.  Pats.  212J209,  215,907,  217,315,  and  223,713,  1907-1909)  according  to  which  the  sulphur 
of  the  purifying  mixture  is  utilised  by  converting  it  into  S02  by  prolonged  treatment  with  a 
stream  of  air.  The  air  is  then  passed  into  the  ammonia  water  used  for  Avashing  the  gas,  ammonium 
sulphite  and  afterwards  the  bisulphite  being  formed.  At  this  point  the  crude  gas  is  washed 
with  this  bisulphite  solution,  which  fixes  the  ammonia  with  formation  of  ammonium  sulphite, 
this  being  again  treated  with  the  air  and  S02 ;  this  process  is  repeated  until  the  solution  deposits 
ammonium  sulphite  (less  soluble  than  the  bisulphite),  which  already  contains  60  per  cent,  of  the 
sulphate,  formed  by  oxidation  with  atmospheric  oxygen.  By  further  oxidation  in  the  air  the 
formation  of  sulphate  is  almost  completed,  the  residual  sulphite  being  removed  by  sublimation 
at  a  temperature  below  100°.  Ammonium  sulphite,  (NH4)2S03,  has  a  pronounced  alkaline  reac- 
tion and  exhibits  little  stability  either  in  solution  or  in  the  crystalline  state ;  in  the  air,  and 
especially  in  the  hot,  it  gives  up  ammonia  and  readily  absorbs  S02  to  form  the  bisulphite  : 
(NH4)2S03  +  S02  +  H20  =  2NH4HS03.  The  latter  also  is  unstable  and  readily  loses  SO2, 
while  NH3  re-converts  it  into  the  sulphite  :  NH4HS03  +  NH3  =  (NH4)2S03.  Owing  to  this 
instability,  the  fixation  of  the  ammonia  with  SO2  according  to  the  equation,  2NH3  +  S02  +  H20 
=  (NH4)2S03,  is  incomplete.  This  process  was  improved  by  Drch'chmidt  and  tested  in  the 
municipal  gasworks  at  Berlin.  The  crude  gas  was  passed  in  a  scrubber  through  the  washing 
liquid  containing  the  ammonium  bisulphite  with  ferric  oxide  in  suspension,  the  ammonia  being 
fixed  with  formation  of  ammonium  sulphite  (see  above)  and  the  hydrogen  sulphide  with  partial 
separation  of  sulphur :  Fe2O3  -f-  3H2S  =  3H20  +  2FeS  +  S.  When  the  oxide  is  exhausted, 
it  is  oxidised  together  with  the  sulphur  in  a  furnace  to  regenerate  ferric  oxide  and  SO2 : 
2FeS  -f  07  =  Fe203  +  2S02.  This  SO2,  mixed  with  air,  is  passed  into  another  scrubber  charged 
with  the  ammonium  sulphite  solution  from  the  first  scrubber;  this  results  in  regeneration  of  the 
ammonium  bisulphite,  which  passes  to  the  first  scrubber,  the  process  being  thus  continuous. 
Oxidation  of  the  sulphite  to  sxilphate  is  effected  without  a  special  furnace. 


EXHAUSTERS,     REGULATORS 


53 


to  be  raised  again,  and  so  on.  The  gas  to  be  washed  enters  at  the  orifice  A,  traverses  the 
spray  in  each  chamber  and  rises  from  one  chamber  to  the  next  above  through  the  aper- 
tures a,  through  which  the  liquid  introduced  at  D  or  E  passes  down  ;  the  gas  finally  issues 
at  B.  A  Feld  washer  -with  seven  chambers  1  metre  in  diameter  is  capable  of  washing 
40,000  cu.  metres  of  gas  per  day.  At  Pompey,  near  Nancy,  three  Feld  washers  6  metres 
high  and  3  metres  in  diameter  were  used  before  the  war  to  wash  3,750,000  cu.  metres  of 
blast  furnace  gases  per  twenty-four  hours. 

After  removal  of  the  hydrogen  sulphide,  the  gas  still  contains  a  certain  quantity  of 
carbon  disulphide  (30  to  150  grams  per  100  cu.  metres,  according  to  the  quality  of  the 
coal  used),  which  is  not  easy  to  separate,  and  on  combustion  yields  SO2,  this  attacking 
metal.  In  1913  Knoevenagel  and  Rcis  proposed  to  eliminate  the  CS2  by  means  of  the 
sodiocellulose  from  which  sodium  xanthate  is  formed  (see  later,  Viscose  silk),  but  it  is 
necessary  first  to  remove  the  CO2  from 
the  gas  (by  potassium  carbonate,  see 
Vol.  I.,  p.  477,  and  the  last  traces  by 
lime).  The  sodium  xanthate  may  be 
utilised  by  regeneration  of  the  cellulose 
by  suitable  washing  and  dissolving  it 
in  concentrated  formic  acid  to  give 
formylcellulose,  which  constitutes  a 
substitute  for  celluloid.  Ten  tons  of 
sodium  xanthate  fix  the  1-25  tons  of 
CS2  contained  in  100,000  cu.  metres  of 
gas.  The  gas  purified  in  this  way  still 
retains  a  small  proportion  of  sulphur 
compounds  (one-fourth  or  one-nfth  as 
much  as  the  original  CS2),  but  these 
are  not  H2S  or  CS2,  and  cannot  be 
eliminated. 

After  purification  the  gas  passes 
through  large  meters  to  the  gaso- 
meters, after  traversing  a  glass  bell-jar 
in  which  is  suspended  a  strip  of  moist 
lead  acetate  paper  for  the  detection 
of  H2S.  Gas  well  purified  contains  less 
than  2  grams  of  ammonia  and  less  than 
45  grams  of  naphthalene  per  100  cu. 
metres. 

In  order  to  diminish  the  quantity 
of  carbon  monoxide  in  gas,  L.  Vignon 
(1911)  proposes  to  heat  it  over  lime 
and  with  steam,  by  which  means  non- 
poisonous  hydrocarbons  are  formed 
(see  note,  p.  58). 

EXHAUSTERS.  To  regulate  the  pressure  of  the  gas  in  the  retorts  and  other  parts 
of  the  plant,  exhausters  are  placed  between  the  condensers  and  the  tar  separators,  or  even 
.after  the  scrubbers.  Sometimes  a  bell-aspirator  is  used,  consisting  of  a  bell  immersed 
in  water  and  capable  of  being  raised  and  lowered  mechanically,  and  thus,  by  means  of 
suitable  valves  in  the  lid,  of  acting  both  as  exhauster  and  as  compressor.  There  are  also 
piston  exhausters,  others  similar  to  exhaustion  pumps  working  by  eccentrically  moving 
blades  (Beale  type),  etc.  The  so-called  Korting  injectors,  which  make  use  of  steam-jets, 
are  also  used  as  exhausters. 

PRESSURE  REGULATORS.  Since  the  development  of  gas  cannot  be  regulated 
in  the  retorts,  whilst  the  working  of  the  exhausters  is  uniform,  there  may  at  certain  times 
•be  an  excess  pressure  generated,  especially  if  the  exhausters  cease  working  or  the  pipes 
become  obstructed.  Hence,  so-called  pressure  regulators  are  employed. 

To  give  an  idea  of  one  of  these  simple  and  ingenious  devices,  it  is  shown  in  Fig.  63  how 
this  regulator  is  combined  with  a  Korting  steam  exhauster  :  d  is  the  exhauster,  which 
receives  steam  from  a  valved  tube,  h,  connected  with  a  bell,  I,  with  a  water-seal^  The 


j?IG 


FIG.  63. 


54  ORGANIC    CHEMISTRY 

gas  from  the  tube  a  passes  through  the  exhauster  to  the  pipe  g.  If  an  excessive  pressure 
develops  in  the  main  a,  the  gas,  by  means  of  the  tube  TO,  raises  the  bell  I,  which  in  its  turn 
effects  a  wider  opening  of  the  steam- valve  and  so  increases  the  exhaustion.  If  the  pressure 
exceeds  a  certain  limiting  value,  a  spring  valve  or  partition  in  n  opens  automatically,  and 
the  gas  discharges  also  by  n  into  the  pipe  g. 

GASOMETERS.  These  are  formed  of  large  sheet-iron  bells  fitting  one  in  the  other 
and  forming  a  perfect  water-seal  when  they  are  inverted  in  a  brick  and  cement  reservoir 

of  water.  To  economise  water,  the 
reservoir  is  partially  filled  up  by  a 
brickwork  cone  (termed  the  "  dump- 
ling "),  starting  from  the  periphery  at 
the  base  and  rising  towards  the  centre, 
as  shown  in  Fig.  64 ;  the  gas  exit  and 
entry  pipes  project  a  little  above  the 
surface  of  the  liquid.  At  a  certain 
point  (not  shown  in  the  figure)  these 
two  pipes  can  be  put  into  direct  com- 
munication, so  that,  in  case  of  accident 
to  the  gasometer,  the  gas  may  still  be 
led  to  the  mains  without  interrupting 
the  work. 

To  economise  in  the  number  and 
size  of  the  reservoirs  and  to  have 
gasometers  of  considerable  capacity, 
so-called  telescopic  gas-Jiolders  are  now 

used.  These  consist  of  several  concentric  bells  (five  or  six),  of  which  only  the  smallest 
is  covered,  whilst  the  others  are  caught  up  peripherally  during  the  rising  (or  filling  with 
gas),  forming  a  water-seal  all  round,  as  shown  in  Fig.  65.  In  order  that  the  bells  may  rise 
centrally  they  are  furnished  outside  with  pulleys  running  along  vertical  iron  guides.  The 
pressure  of  gas  in  the  gasometer  may  be  calculated  from  the  weight  of  the  bell  outside  the 
water,  together  with  the  surface  and  diameter  of  the  bell  itself. 

The  pressure  in  the  gasometer  or 
mains  may  be  registered  automatically 
by  placing  them  in  communication  with 
an  automatic  pressure-measure  like  that 
shown  in  Fig.  66.  In  this  the  gas  raises 
or  lowers  a  bell  fitted  with  an  index 
which  registers  the  different  pressures 
during  the  day  on  a  paper  wound  round 
a  cylinder  rotated  once  in  twenty-four 
hours  by  clockwork. 

There  are  other  forms  of  pressure 
indicators,  but  the  above,  although  old 
(in  principle),  is  still  largely  used,  being 
simple  and  exact. 

In  order  to  avoid  the  serious  con- 
sequences contingent  on  a  gasometer 
reservoir  cracking  or  leaking,  iron 
reservoirs  built  above  ground  are  now  Fic._64. 

preferred,  the  slightest  escape  being  then 

observable  and  remediable  at  any  moment.  Such  a  suspended  telescopic  gasometer  is 
shown  in  Fig.  65. 

To  meet  the  enormous  daily  consumption  of  gas  in  large  cities  moi'e  and  more  capacious 
gas-holders  are  required — sufficient  to  contain  three  or  four  days'  supply  and  so  avoid  the 
inconveniences  of  an  interruption  of  work  (from  damage,  strikes,  etc.).  In  Milan, 
prior  to  1908,  the  largest  of  the  gasometers  (measuring  altogether  150,000  cu.  metres) 
had  a  capacity  of  26,000  cu.  metres;  after  1908,  at  the  Bovisa  (Milan)  works  a  new  one 
was  brought  into  use  which  holds  80,000  cu.  metres  and  cost  little  less  than  £40,000.  The 
firm  jjf  Krupps  constructed  for  their  own  works  a  gasometer  holding  37,000  cu.  metres ; 


PRESSURE     REGULATORS 


55 


the  largest  at  Berlin  contains  80,000  cu.  metres;  that  of  Chicago  120,000  cu.  metres;  and 
the  last  built  at  New  York  has  a  cement  reservoir  and  a  capacity  of  500,000  cu.  metres ; 
in  London  in  1888  one  was  built  holding  230,000  cu.  metres,  and  in  1892  another  with 
six  bells,  containing  345,000  cu.  metres  and  having  a  diameter  at  the  base  of  95  metres; 
the  last  built  at  Vienna  contains  250,000  cu.  metres.  Naturally  these  gas-holders  represent 
large  amounts  of  capital,  the  cost  even  for  capacities  of  30,000  to  40,000  cu.  metres  being 
tens  of  thousands  of  pounds.  Fig.  67  shows  diagrammatically  the  arrangement  of  a 
gasworks  at  the  middle  of  the  nineteenth  century. 

PRESSURE  REGULATORS  FOR  CONSUMERS.  In  order  that  consumers  may 
have  a  uniform  pressure  in  their  pipes  and  obtain  regular,  non-oscillating  flames  with  a 
normal  consumption  of  gas,  it  is  necessary  to  use  pressure  regulators  where  the  principal 
mains  leave  the  works,  these  regulating  the  pressure  automatically  even  when  the 
consumption  is  at  its  maximum  or  minimum.  Since  gas  is 
lighter  than  air,  the  pressure  is  regulated  more  easily,  and 
the  flow  facilitated,  by  constructing  the  works  at  the 
lowest  point  of  the  town.-  In  the  gas-holder  the  pressure 
is  usually  15  cm.  of  water,  whilst  in  the  mains  it  is  about 
2  cm. 

A  regulator  as  ingenious  as  it  is  simple  was  devised  by 
Clegg  and  is  in  general  use  at  the  present  time  (Fig.  68). 
In  a  metal  cylinder,  a,  filled  with  water,  a  bell,  6,  may  be 
raised  or  lowered  according  as  the  gas  supplied  at  /  has  a 
greater  or  less  pressure;  The  pressure  in  the  bell  may'  be 
varied  by  altering  the  size  of  the  aperture  in  tube  /  by 


FIG.  65. 


FIG.  66. 


which  the  gas  is  admitted.  The  orifice  i  at  the  upper  end  of  /  can,  indeed,  be  closed  to  a 
greater  or  less  extent  by  a  metal  cone,  e,  attached  by  a  chain  to  the  bell,  with  which  it  rises 
if  the  pressure  is  excessive — thus  diminishing  i  and  hence  the  pressure  in  the  bell — or  falls 
if  the  pressure  diminishes  too  much,  more  gas  then  entering  through  i  and  the  normal 
pressure  being  thus  re-established.  This  normal  pressure  may  be  fixed  according  to  the 
needs  of  any  particular  time,  by  placing  on  the  bell  weights,  d,  calculated  to  give  the 
required  pressure.  By  means  of  this  simple  regulator  the  gas  issues  from  h  at  a  constant 
pressure  and  may  be  passed  immediately  into  the  mains. 

In  general,  however,  the  pressure  is  not  the  same  in  all  the  mains,  but  diminishes  as 
the  distance  from  the  works  increases.  It  is,  however,  not  advisable  to  have  the  pressure 
too  high,  since  the  losses  due  to  unavoidable  leaks  in  the  pipes  are  greater  the  higher  the 
pressure,  and  the  latter  is  usually  maintained  at  15  to  20  mm.  of  water  at  the  points  most 
remote  from  the  works.1 

1  Leaks  in  the  street  mains  are  detected  by  driving  into  the  ground  glass  or  iron  tubes  con- 
taining paper  soaked  in  palladious  chloride  or  iodic  anhydride,  which  is  darkened  by  the  action 
of  CO  (see  Vol.  I.,  p.  484). 


56 


ORGANIC    CHEMISTRY 


TRANSPORT  OF  GAS  TO  A  DISTANCE.  Attempts  have  been  made  to  convey 
gas  to  great  distances  under  1  or  even  2  atmospheres'  pressure,  in  order  that  smaller  pipes 
might  be  used.  Under  these  conditions,  however,  increased  leakage  occurs,1  while  some- 
times liquid  and  solid  matter  separates  and  obstructs  the  pipes.  Avoidance  of  this  incon- 
venience requires  special  purification  of  the  gas  and  its  subjection  to  intense  cooling  (accord- 
ing to  Lipinsky's  Ger.  Pat.  257,534  of  1912,  the  CO  is  transformed  into  methane  by 
the  method  of  Sabatier  and  Senderens  :  see  note,  p.  58),  the  naphthalene  being  carefully 
separated.  Gas  produced  in  vertical  retorts  is  best  suited  for  distribution  under  pressure. 

In  order  to  render  the  distribution  of  the  gas  to  considerable  distances  more  economical, 
attempts  have  been  made  to  employ  a  pressure  of  1  to  1-5  atmos.  on  the  gas,  the  latter 
being  preferably  from  vertical  retorts  and  as  free  as  possible  from  naphthalene. 

GAS-METERS.  These  are  used  to  measure  the  gas  in  factories  and  private  houses, 
since  nowadays  payment  is  according  to  the  volume  consumed  and  not  according  to  the 


FIG.  67. 

C  =  horizontal  retorts;  B  —  hydraulic  main  for  separating  the  tar;  D  =  tubes  for  cooling 
gas ;  0  —  washing  towers  (scrubbers) ;  M  =  chambers  containing  Laming  mixture  for  purifying ; 
G  —  single-lift  gasholder;  SS  =  entry  and  exit  gaspipes. 

number  of  burners,  as  was  once  the  custom.  Dry  meters  have  disappeared  almost  every- 
where, general  use  being  made  of  the  water  meters  devised  by  Clegg  and  by  Malam,  and 
since  improved  so  that  they  are  now  perfect  gas-measurers.  The  principle  on  which  their 
working  is  based  is  shown  clearly  by  Fig.  69,  representing  an  old  form  of  the  Malam  meter. 
A  cylindrical  chest,  X,  half-filled  with  water,  contains  a  drum  rotatable  about  a  horizontal 
axis  and  divided  into  four  chambers,  A,  B,  C,  and  D,  communicating  at  the  centre  by 
means  of  the  narrow  slits  b,  and  opening  into  the  periphery  at  X  by  the  slits  c.  The  gas 
is  led  by  the  tube  a  into  the  central  part  of  the  drum  and,  in  the  position  shown  in  the 
figure,  communicates  only  with  the  slit  b  of  the  chamber  D ;  the  latter  is  thus  slowly  filled 
with  gas  (which  has  a  slight  pressure),  the  drum  being  thereby  raised  and  water  caused  to 
escape  from  c.  Thus  the  chamber  D  becomes  filled  with  gas  in  the  position  occupied  by  C, 

1  Gasworks  always  experience  gas  losses,  indicated  by  the  difference  between  the  amounts 
registered  by  the  works  meters  and  those  shown  by  all  the  meters  of  their  customers.  Such 
losses  vary  from  1-5  to  18  per  cent.,  and  are  due,  not  solely  to  leaks  in  the  pipes,  butmore  especially 
to  errors  in  the  meters,  to  condensation  of  water  in  the  pipes  caused  by  differences  of  temperature, 
etc.  In  Pennsylvania  these  losses  are  only  1-9  per  cent.,  in  Virginia  18  per  cent.,  in  Bradford 
4-8  per  cent.,  in  Glasgow  8-7  per  cent.,  in  Stuttgart  (Germany)  1-2  per  cent.,  and  in  Essen 
13  per  cent.  Losses  due  to  leakage  may  be  diminished  to  one-tenth  of  their  usual  amount  by 
using  pipes  welded  autogenously  every  10  metres  into  lengths  of  60  metres. 


METERS 


57 


which  has  allowed  its  gas  to  escape  gradually,  the  rotation  indicated  by  the  arrow  having 
caused  it  to  fill  with  water  through  the  corresponding  slit  6.  Subsequently  the  gas  fills 
the  next  chamber,  A,  which  displaces  D,  and  so  on.  The  gas  passing  through  this  apparatus 
proceeds  along  the  tube  K  to  the  consumer's  burners.  If  all  the  taps  are  turned  off,  the 
drum  cannot  allow  the  gas  to  escape  from  it,  and  hence  does  not  turn.  The  chambers 
have  definite  volumes,  and  if  the  axis  of  the  drum  is  connected  with  a  suitable  magnifying 


FIG.  68. 


FIG.  09. 


FIG.  70. 


apparatus  the  number  of  turns  of  the  drum  and  consequently  the  volume  of  gas  traversing 
it  may  be  measured. 

This  apparatus  exhibits  many  structural  defects  which  cause  inaccurate  measure- 
ments, and  are  now  avoided  by  the  meter  shown  in  Figs.  71,  72,  and  73.  Here 
the  drum  has  transverse  walls  which  are  inclined  and  not  parallel  to  the  axis  (Fig.  70, 
V,  W),  so  that  the  filling  with  the  gas  or  water  and  the  discharge  take  place  gradually 

t  I       J 


FIG.  71. 


FIG.  72. 


and  do  not  cause  oscillation  of  the  flame.  The  gas  enters  by  the  tube  I  into  the 
division  k  (Figs.  71  and  72)  and  passes  into  E  through  the  orifice  i,  regulated  by  a  floating 
valve,  h.  Thence  the  gas  goes  to  the  ante-chamber  B  by  way  of  the  elbow-tube  n  x,  opening 
above  the  level,  W,  of  the  water.  The  aperture  o  connecting  the  tube  x  with  the  ante- 
chamber is  large  enough  to  admit  of  the  passage  of  the  axis  of  the  drum,  but  remains 
closed  owing  to  the  level  of  the  water  being  above  it.  As  the  slits  of  the  drum  gradually 
present  themselves,  the  gas  enters  successively  the  chamber  of  the  drum  from  one  side 
and  issues  at  the  other  into^the  outer  casing  A,  then  passing  through  the  tube  g  to  the 


58 


ORGANIC    CHEMISTRY 


gaspipes.  Water  (or  better,  a  mixture  of  water  and  glycerine,  which  does  not  freeze)  is 
introduced  by  the  opening  F,  the  level  of  the  liquid  being  fixed  by  the  tube  n,  so  that  the 
flow  of  gas  through  the  valve  i  is  regulated ;  the  excess  of  water  is  discharged  by  the  tube  n 
and  passes  into  the  reservoir  m,  thence  by  the  tube  t  to  S,  the  orifice,  u,  of  which  is  left 
open  while  the  water  is  being  added.  The  axis  of  the  rotating  drum  has,  at  one  end,  a 
continuous  screw,  a  (Fig.  73),  which  moves  a  toothed  wheel,  a;  the  latter,  by  means  of  the 
axle  e,  produces  rotation  of  a  clockwork  arrangement  in  F,  so  constructed  that  one  wheel 
indicates  litres  and  tens  of  litres,  another  cubic  metres,  a  third  tens  of  cubic  metres,  and  a 
fourth  hundreds  of  cubic  metres. 

The  last  few  years  have  seen  the  successful  introduction  of  the  new  dry  meters  (which, 
however,  rapidly  become  less  exact  than  the  ordinary  wet  meters,  when  in  use)  and  of 
automatic  meters,  of  which  Berlin  alone  contained  84,000  in  1905.  By  placing  a  10-pfennig 
piece  into -one  of  these  automatic  metres,  500  litres  of  gas  are  supplied.  In  1906  Berlin 
had,  in  addition,  191,000  ordinary  meters. 

YIELD,  VALUE,  AND  PRICE  OF  GAS.  These  vary  with  the  nature  of  the  coal 
used  and  with  the  conditions  of  carbonisation.  In  the  large  gasworks  of  the  principal 
European  towns  the  yields  (per  ton  of  coal  carbonised)  usually  vary  between  the  following 
limits  :  coke,  63  to  76  per  cent.,rmore  commonly  69  to  71  per  cent.  (1  hectolitre  weighs 

34  to  37  kilos);  tar,  4  to  6  per  cent. ;  ammonia  liquors, 
9-8  to  12-5  per  cent.  (i.  e.,  0-8  to  1  kilo  of  ammonium 
sulphate);  gas,  25  to  31  cu.  metres  (of  sp.  gr.  0-360 
to  0-480).  At  Berlin  every  ton  of  coal  yielded  on  the 
average  287-3  cu.  metres  in  1900,  305  in  1901,  320  in 
1902,  and  324-4  in  1904,  in  addition  to  690  kilos  of 
coke,  54  kilos  of  tar,  and  120  kilos  of  ammonia  liquors. 
In  many  gasworks  at  the  present  day,  instead  of 
installing  new  plant,  increased  consumption  of  gas  is 
met  by  mixing  with  water-gas  (or  blue  gas),  and  as  the 
calorific  value  of  this  is  only  about  one- half  that  of 
coal-gas,  benzene  or  heavy  petroleum  vapours  are  also 
added.  Water-gas  generators  give  a  rapid  production, 
do  not  form  naphthalene  or  tar,  and  yield  a  gas  costing 

less  than  half  that  of  ordinary  gas ;  this  is,  however,  very  rich  in  carbon  monoxide,  which 
has  caused  numerous  cases  of  poisoning  in  the  United  States,  so  that  the  medical  men 
instituted  in  1910  a  campaign  to  forbid  the  use  of  water-gas.1  Nevertheless,  in 

1  To  obtain  a  candle-power  of  16  with  a  mixture  of  two -thirds  of  coal  gas  and  one -third  of 
water-gas,  40  grams  of  benzene  must  bo  added  per  cu.  metre  (4  grams  of  benzene  per  cu.  metre 
increase  the  luminosity  by  1  candle-power),  the  cost  being  about  G-5d.  per  cubic  metre  (with 
benzene  at  £10  per  ton ). 

During  the  European  War  the  benzene  and  toluene  (about  25  grams  of  the  two  out  of  the 
35  grams  present  per  cubic  metre)  were  extracted  in  all  countries  from  coal-gas  and  from  coke 
furnace  gas  (see  Vol.  I.,  p.  451)  by  washing  the  gas  in  towers  containing  circulating  heavy  tar 
oil  (b.-pt.  250°  to  300°),  which  constitutes  a  good  solvent  for  these  substances;  the  benzene 
and  toluene  are  afterwards  distilled  off  from  the  oil,  which  is  used  again  (see  later,  Benzene). 
Naturally  the  gas  loses  in  heating  power  and  luminosity  by  this  process. 

Water-gas,  reinforced  with  benzene  and  mineral  oils,  costs  about  15  per  cent,  more  than 
ordinary  gas,  but  presents  various  advantages  :  without  expensive  plant,  a  production  higher 
than  the  capacity  of  the  works  may  be  supplied ;  part  of  the  coke  is  utilised,  over-production 
and  consequent  lowering  of  the  price  being  thus  avoided ;  less  consumption  of  coal  for  gas  and 
hence  less  danger  of  rise  in  price  of  coal;  less  labour;  rapid  production  even  in  the  event  of  a 
strike.  In  England  over  500,000,060  cu.  metres  were  produced  in  1910  and  in  the  United  States 
2200  million  cu.  metres.  Water-gas  may  be  rendered  less  injurious  by  diminishing  the 
proportion  of  CO  by  the  processes  mentioned  in  Vol.  I.,  pp.  141,  484,  and  486,  or,  as  at  the  Lyons 
gasworks,  by  passing  the  gas  mixed  with  steam  over  ferric  oxide  at  400°.  to  500°  :  Fe203  +  4CO  + 
H.jO  —  4CO2  +  H2  +  2Fe,  the  C02  being  then  removed  by  washing  with  water.  Water-gas 
contains  85-4  per  cent.  H,  9-4  per  cent.  CO,  and  5-2  per  cent.  0  and  N,  has  the  sp.  gr.  0-18  and 
the  calorific  value  2490  Cals.  per  cu.  metre,  and  is  most  suitable  for  airships  (see  note,  p.  40). 

Attempts  have  also  been  made  to  diminish  the  content  of  CO  by  means  of  the  Sabatier  and 
Senderens  process  (see  p.  35),  i.  e.,  by  converting  it  into  methane  by  the  action  of  finely  divided 
nickel  at  250° ;  for  this  conversion  to  be  complete  the  ratio  between  the  CO  and  the  H2  must 
be  1  :  5  (water-gas  actually  contains  about  40  per  cent,  of  CO  and  52  per  cent,  of  H2  by  volume). 
The  nickel  catalyst  is  rapidly  paralysed  by  the  sulphur  and  by  the  carbon  separating.  These 
inconveniences  are  overcome  by  the  Cedford  prccess,  in  which  the  gas  is  compressed  to  10  atmos. 
in  presence  of  water,  which  dissolves  most  of  the  C02,  the  rest  of  the  latter  being  fixed  by  lime. 


FIG.  73. 


GASSTATISTICS  59 

almost  all  the  large  gasworks  of  different  countries  a  mixed  gas  containing  15  to  20  per 
cent,  of  water-gas  is  made. 

The  cost  of  manufacture  of  coal-gas  varies  with  the  different  factors  affecting  its  pro- 
duction, especially  with  the  size  of  the  works,  the  prices  of  coal  and  labour  and  the  greater 
or  less  completeness  with  which  the  secondary  products  (ammonia,  cyanides,  sulphur, 
tar,  etc.)  are  utilised.  In  Berlin  the  mean  cost  of  manufacture  before  the  war  was  0-75d. 
per  cubic  metre,  while  at  Milan  it  is  about  Q-85d.1  Gas  varies  in  price  in  different  towns 
from  l-15d.  to  3-8d.  per  cubic  metre  (32d.  to  IQOd.  per  1000  cu.  ft. ) ;  in  Paris  it  is  1-9,  in  Milan 
1-25,  in  Oneglia  2-9,  in  Messina  3-2,  in  Venice  3-5,  in  Catania  3-8,  and  in  Naples  3-  Id.  per 
cubic  metre.  (In  England  often  much  cheaper. — Translator. ) 

During  the  war  prices  were  in  some  cases  trebled,  and  in  Italy  the  output  was  largely 
diminished  owing  to  scarcity  of  coal ;  in  1919  high  prices  still  prevailed  everywhere. 

STATISTICS.  The  consumption  of  lighting  gas  (subject  to  tax)  in  Italy  in  1902  was 
139  million  cu.  metres,  and  exempt  from  taxation  (for  engines,  etc. )  56  million  cu.  metres, 
and  in  1909,  318  million  cu.  metres  (£2,040,000),  obtained  from  1  million  tons  of  coal, 
51,000  tons  of  tar,  and  710,000  tons  of  coke  being  recovered.2 

In  1906,  16  million  tons  of  coal  were  carbonised  in  Great  Britain  to  procure  4300  million 
cu.  metres  of  illuminating  gas,  and  in  1909,  4760  million  cu.  metres  were  produced,  besides 
588  million  cu.  metres  of  carburetted  water-gas. 

In  1859,  Germany  consumed  44  million  cu.  metres  of  gas,  in  1879,  about  350  million, 
in  1889,  about  500  million,  in  1899,  almost  1200  million  (from  about  3,500,000  tons  of  coal), 
in  addition  to  1  million  tons  of  petroleum,  corresponding  with  more  than  2000  million  cu. 
metres  of  gas.  In  1905,  310  large  gasworks  used  4,500,000  tons  of  coal,  of  which  one-fourth 
was  imported  from  England,  and  700  other  small  works  carbonised  a  total  of  1,000,000  tons ; 
in  1910,  the  output  of  gas  was  2200  million  cu.  metres,  made  in  1200  works,  representing 
a  capital  of  £80,000,000  (£12,000,000  for  Berlin  and  £640,000  for  Munich),  the  coal  carbonised 

The  remaining  gas  is  cooled  to  the  temperature  of  liquid  air  by  means  of  a  Linde  machine  (see 
Vol.  I.,  p.  343),  most  of  the  CO  and  N2  being  thus  removed  in  the  liquid  state  and  the  sulphur 
compounds  as  solids;  the  residual  gas  contains  17  per  cent,  of  CO,  and  the  liquefied  CO  is  used 
for  gas-engines.  The  gas  containing  17  per  cent,  of  CO  is  passed  into  a'quartz  tube  filled  with 
pumice  coated  with  finely  divided  nickel  and  heated  at  280°  to  300°,  all  the  CO  being  thus  trans- 
formed into  CH4  (if  carbon  is  deposited  on  the  nickel,  the  gas  current  is  slackened  :  C  +  2H2  — 
CH4).  The  final  gas  has  the  following  percentage  composition  :  CO»,  less  than  1 ;  CO,  less  than 
0-2 ;  CH4, 28  to  32 ;  H,  60  to  65 ;  N,  6  to  7,  its  calorific  value  being  4100  to  4300  Cals.  By  repeated 
addition  of  CO,  a  gas  containing  76  per  cent,  of  CH4  may  be  obtained.  This  Cedford  gas  may 
be  added  with  impunity  to  illuminating  gas. 

1  We  give  here  an  approximate  industrial  balance-sheet  referred  to  one  ton  of  coal  and  to 
the  conditions  employed  in  the  Milan  gasworks  prior  to  the  war  : 

(a)  Receipts  :  264  cu.  metres  of  gas  (290  actually  produced,  less  9  per  cent,  for  escapes  and 
consumption  in  works)  at  0-13  lira  gives  34-32  lire;   700  kilos  of  coke,  22-40  lire;   45  kilos  of 
tar,  1-35  lire ;  9  kilos  of  ammonium  sulphate,  2-70  lire;  cyanides,  graphite,  slag,  ashes,  0-06  lira. 
Total  receipts,  60-83  lire. 

(b)  Expenditure  :    1  ton  of  coal,  30  lire;   coke  for  heating  the  furnaces  (160  kilos),  5-12  lire; 
purifying  and  Laming  mixtures,  0-37  lira  ;  sulphuric  acid  and  expenses  for  ammonium  sulphate, 
1-44  lire;  salaries  and  wages,  10-58  lire ;  taxes,  0-67  lira;   fire  insurance,  0-091  lira ;  workmen's 
insurance,  0-175  lira;   general  expenses,  1-10  lire;   maintenance  of  works,  private  and  public 
expenses,  new  plant,  3  lire;  maintenance  of  meters  and  sundry  other  expenses,  0-090  lira.     Total 
expenditure,  53-23  lire. 

Net  profit,  about  7-60  lire. 

2  At  Milan  in  1903,  40  million  cu.  metres  of  gas  were  produced,  in  1905  about  47  million  cu. 
metres,  in  1908  about  61  million  cu.  metres  (7000  incandescent  gas  lamps  being  used  for  public 
lighting),  in  1913,  62,433,500  cu.  metres,  in  1915,  65,571,660  cu.  metres  (3,314,200  for  power 
purposes),  and  in  1916,  60,136,140  cu.  metres.     Paris  alone  consumes  annually  350  million  cu. 
metres,  two-thirds  by  night  and  one-third  by  day  (for  engines,  etc.),  and  Berlin  used  in  1908 
about  260  million  cu.  metres  and  in  1911  more  than  530  millions  (in  this  city  gas  manufacture  is 
municipalised,  and  the  community  draws  an  annual  profit  of  about  £350,000).     From  1886  to 
1904,  the  consumption  in  Brussels  increased  from  15  to  39  million  cu.  metres,  that  is,  from  85  to 
204  cu.  metres  per  head  per  annum.      In  Budapest  300,000  cu.  metres  of  gas  per  day  were 
consumed  in  1913. 

The  various  sources  of  light  used  to  supply  the  needs  of  Paris  in  1889  were  in  the  following 
proportions  :  wax,  tallow,  stearine,  1-6  per  cent.;  vegetable  oils,  4-5  per  cent.;  petroleum,  17-7 
per  cent.;  electricity,  18-9  per  cent.;  gas,  57-3  per  cent.  In  Berlin,  where  the  consumption 
of  gas  in  1889  was  117  million  cu.  metres  and  where  54,000  tons  of  petroleum  were  used  for 
lighting  purposes,  the  proportions  were  as  follows  :  petroleum,  50  per  cent. ;  gas,  47  per  cent. ; 
electricity,  3  per  cent.  In  1910  the  consumption  of  gas  in  Berlin  was  182,500,000  cu.  metres, 
containing  32,500,000  cu.  metres  of  water-gas  obtained  from  15,100  tons  of  coke. 


60  ORGAN  1C    CHEMISTRY 

amounting  to  about  6,300,000  tons.  In  1913,  the  production  of  gas  in  Germany  reached 
3160  million  cu.  metres,  10  million  tons  of  coal  being  used  1  and  by-products  to  the  value 
of  £4,800,000  obtained. 

In  the  United  States  600  million  cu.  metres  of  gas  were  produced  in  1900,  and  more 
than  870  million  in  gasworks  in  1905,  besides  275  million  in  coke  works  and  2200  million  of 
water-gas. 

In  1909,  there  were  in  the  United  States  1296  gasworks  (1019  in  1904)  with  a  capital 
of  £180,000,000;  the  output  of  gas  and  by-products  was  valued  at  £33,600,000,  and  the 
numbers  of  workpeople  and  officials  employed,  37,200  and  13,500  respectively.  The  gas 
produced  amounted  to  4200  million  cu.  metres  (including  water-gas,  which  constituted 
53  per  cent,  of  the  total). 

In  Japan  the  lighting  gas  industry  was  started  only  in  1901,  44  million  cu.  metres  being 
produced  in  1907. 

In  Switzerland,  500,000  tons  of  coal  are  carbonised  annually  for  making  coke  and  gas, 
30,000  tons  of  tar,  1500  of  naphthalene,  450  of  benzene  and  toluene,  and  75  of  phenol  also 
being  obtained.  • 

The  manufacture  and  nature  of  air-gas,  producer  gas,  Riche  gas,  water-gas,  etc.,  are 
described  in  Vol.  I.,  pp.  486  et  seq. 

PHYSICAL  AND  CHEMICAL  TESTING  OF  ILLUMINATING  GAS.  As  regards 
the  determination  of  CO,  CO2,  N,  and  0,  Orsat's  apparatus  (see  Vol.  I.,  p.  463)  gives  good 
results.  The  estimation  of  hydrogen  is  effected  with  the  ordinary  Hempel  burette  or 
simply  by  determining  the  diminution  in  volume  of  the  gas  after  passing  it  through  a 
capillary  tube  containing  palladinised  asbestos  heated  at  about  100°  (see  Vol.  I.,  p.  135). 
Then  comes  the  determination  of  unsaturated  and  aromatic  hydrocarbons,  which  are  all 
absorbed  by  fuming  sulphuric  acid,  the  gas  being  measured  before  and  after  the 
absorption  in  the  Hempel  burette  (the  gas  being  washed  with  potash  after  the  absorp- 
tion). The  methane  is  estimated  by  exploding  the  gas  remaining  in  the  burette  with  a 
known  volume  (in  excess)  of  oxygen  by  means  of  an  electric  spark,  2  vols.  of  the  gaseous 
mixture  (gas  +  oxygen)  disappearing  for  every  1  vol.  of  methane,  according  to  the  equation  : 

CH4  +  2O2  =  CO2  +  2H20. 

1  vol.      2  vols.       1  vol.      condenses 

To  estimate  the  ammonia  in  the  purified  gas,  200  litres  of  it  are  passed  through  10  c.c.  of 
N/10  hydrochloric  acid  solution,  the  excess  of  which  is  subsequently  determined  by  titration. 

The  determination  of  the  total  sulphur  compounds  may  be  effected  simply  by  the  method 
given  by  F.  Fischer.2 

1  For  the  production  of  gas  in  Berlin  352,000  tons  of  German  coal  and  397,000  tons  of  English 
coal  were  used  in  1907;  at  the  English  ports  the  coal  cost  8s.  l£d.  per  ton  in  1904  and  11s.  4M. 
in  1909.     The  cost  of  transport  from  the  English  mines  to  Berlin  amounted  to  7s.  %\d.  per  ton, 
whilst  from  the  German  mines  at  Ruhr  to  Berlin  it  exceeded  8s.  lid.     At  the  gasworks  in  Berlin 
the  English  coal  cost  16s.  per  ton,  and  the  German  (from  Silesia)  20s.  per  ton. 

In  1880  only  one-half  of  the  gasworks  were  municipalised,  and  in  1909  two-thirds,  the  profit 
amounting  to  8  to  13  per  cent,  on  the  capital. 

In  Germany  in  1910  35,000  gas-engines  generated  175,000  h.p.  (in  1898  there  were  22,000 
engines),  50  per  cent,  of  the  total  output  of  gas  being  used  for  power  and  heating  purposes  (in 
1898,  33  per  cent.).  It  is  found  profitable  to  erect  a  gasworks  in  Germany  in  centres  containing 
over  3000  inhabitants.  In  1911  the  receipts  of  the  German  Government  on  account  of  taxes 
on  illumination  were  as  follows  :  £108,000  for  carbon-filament  electric  lamps ;  £292,000  for 

metal  filament  (and  Nernst)  lamps ;  £1600  for 
mercury  vapour  lamps  (see  Vol.  L,  p.  687); 
£216,000  for  incandescent  gas  lamps ;  £90,000 
for  arc  lamps  with  pure  carbons ;  £64,000  for  arc 
lamps  with  special  carbons  containing  admixed 
luminous  substances.  In  Germany  between 
April  1,  1911,  and  March  31,  1912,  there  were 
made :  24,791,200  carbon  filament  lamps 
(1,585, 700 imported),  47,212,000  metallic  fila- 
ment lamps  (1,450,000  imported),  130,671 
Nernst  lamps  (output  diminishing),  12,050 
mercury  vapour  lamps  (1500  imported), 

FIG.  74.  126,000,000  Auer  mantles  (35,000  imported), 

8,104,000  kilos  of  pure  carbons  for  arc  lamps, 
and  2,637,000  kilos  of  carbons  with  various  additions. 

2  About  50  litres  of  the  gas  (measured  by  a  good  meter)  are  burned  in  a  small  bunsen  burner,  g 
(Fig.  74),  in  the  drawn-out  bulb,  A,  of  a  bulb-condenser  arranged  as  shown.     All  the  sulphur 
of  the  sulphur  compounds  burns,  forming  sulphurous  and  sulphuric  acids  with  the  water  from 


61 


For  the  complete  analysis  of  gas,  see  Treadwell's  "  Quantitative  Analysis."     The  calorific 
power  may  be  determined  fairly  rapidly  with  the  Junker  calorimeter.1 

the  combustion  of  the  gas,  this  condensing  in  the  bulbs  of  the  condenser  and  being  collected  at 
the  bottom  in  a  beaker  by  means  of  the  tube  e.  The  combustion  is  regulated  so  that  gas  contain- 
ing 4  to  6  per  cent,  of  oxygen  escapes  at  o.  Water  enters  the  condenser  at  z  and  leaves  at  n. 
At  the  end  of  the  operation,  the  bulbs  are  rinsed  out  with  water  and  the  sulphurous  acid  in  the 
liquid  oxidised  by  means  of  pure,  neutral  hydrogen  peroxide  solution;  the  sulphuric  acid  is 
then  titrated  with  N/10  sodium  hydroxide  solution.  If  the  sulphuric  acid  is  estimated  gravi- 

metrically  with  barium  chloride,  the  oxidation  of  the  sulphurous 
acid  must  be  effected  with  hydrogen  peroxide  free  from 
sulphates.  The  quantity  of  sulphuric  acid  found  gives  the  total 
sulphur-content  of  the  gas.  A  well-purified  gas  contains  less 
than  0-5  gram  of  sulphur  per  cubic  metre. 

The  hydrogen  sulphide  is  estimated  separately  by  passing  a 
known  volume  of  the  gas  through  ammoniacal  silver  nitrate 
solution,  which  is  afterwards  acidified  with  a  little  nitric  acid, 
the  silver  sulphide  being  filtered  off,  washed,  dried  at  100°,  and 
weighed. 

The  naphthalene  is  determined,  especially  in  the  crude  gas 
(which  contains  8  to  10  grams  per  cubic  metre),  by  passing  a 
certain  volume  of  the  gas  through  saturated  picric  acid  solution 
and  filtering  off  the  insoluble  naphthalene  picrate,  which  is  then 
boiled  with  water  in  a  current  of  air.  In  this  way  it  decomposes 


FIG.  75. 


FIG.  76. 

into  picric  acid  and  naphthalene,  the  latter  being  passed  into  another  standard  picric  acid 
solution,  the  excess  of  picric  acid  being  determined  with  standard  potassium  iodide  and  iodate 
solution  :  KI03  +  SKI  +  6C6H2(N02)3OH  =  6C6H2(N02)3OK  +  3H20  +  61;  the  iodine  liberated 
is  titrated  with  thiosulphate  solution. 

1  This  consists  (Fig.  76;  section  in  Fig.  75)  of  a  metal  cylinder,  C  (the  letters  refer  in  all  cases 
to  Fig.  76),  which  is  mounted  on  three  feet,  and  inside  which  a  known  volume  of  the  gas  is  burned 
by  means  of  the  bunsen  burner,  n.  The  hot  products  of  combustion  pass  several  times  up  and  down 
the  calorimeter  and  issue  at  the  outlet  8,  which  is  furnished  with  a  valve  and  also  regulates  the 


62  ORGANIC    CHEMISTRY 

The  specific  gravity  sometimes  serves  to  test  the  constancy  in  composition  of  gas  or 
to  compare  two  different  gases;  it  also  gives  a  rough  idea  of  illuminating  power,  since 
the  specific  gravities  of  the  more  highly  light-giving  hydrocarbons — acetylene  (0-920), 
ethylene  (0-976),  propylene  (1-490),  and  benzene  (2-780) — are  higher  than  those  of  the 
non-luminous  components — hydrogen  (0-0695),  methane  (0-559),  etc.  The  specific  gravity 
may  be  determined  rapidly  and  exactly  with  the  Bunsen  effusiometer  (see  Vol.  I.,  p.  40). 

ILLUMINATING  POWER.  There  is  no  absolute  measure  of  the  power  of  different 
sources  of  light,  but  these  may  be  compared  when  a  conventional  unit  has  been  chosen. 

This  standard  of  light  has  been  differently  chosen  in  different  countries  and  has  been 
continually  modified.  Thus  in  England  spermaceti  candles  are  used  of  such  size  that 
six  weigh  1  lb.,  while,  when  burned,  they  lose  7-78  grams  (120  grains)  per  hour  with  a 
flame  45  mm.  in  height.  In  Germany  in  1872  a  paraffin  wax  candle  20  mm.  in  diameter 
was  employed,  the  wick  having  24  threads  and  weighing  0-668  gram  per  metre  and  the 
flame  being  50  mm.  high ;  six  of  these  candles  weighed  1  lb.  Use  is  now  made  in  Germany 
of  the  more  rational  Hefner-Alteneck  lamp,  fed  with  a  liquid  of  constant  composition, 
namely,  amyl  acetate,  the  compact  wick,  8  mm.  in  diameter,  protruding  25  mm.  from 
the  metallic  sheath  holding  it ;  the  flame  is  40  mm.  high.  In  France  and  Italy  the  Carcel 
lamp  is  used,  this  consuming  42  grams  of  purified  colza  oil  per  hour  and  having  a  wick 
which  is  23-5  mm.  in  diameter,  is  formed  of  75  threads,  and  weighs  3-6  grams  per  10  cm. 

The  relative  values  of  these  different  units  are  as  follows  :  1  Carcel  =  9-600  English 
candles  (spermaceti)  =  8-768  German  candles  (paraffin  wax)  =  10-526  Hefner-Alteneck 
flames. 

In  1914  the  French  Government  fixed  as  unit  of  luminosity  the  Violle  decimal  candle, 
defined  as  the  one-twenty-fifth  part  of  the  light  radiated  from  an  area  of  1  sq.  cm.  of  molten 
platinum  at  its  solidifying  point.  The  lumen  would  then  be  the  quantity  of  light  or  the 
luminous  flux  radiated  from  a  source  of  light  equal  to  a  decimal  candle  on  to  a  surface  of 

air-draught.  Passing  in  a  direction  opposite  to  that  of  the  gases  of  combustion  and  in  alternate 
adjacent  chambers  is  a  current  of  water  which  enters  by  w  the  small  reservoir  m,  the  excess  being 
carried  off  by  the  overflow,  b,  while  a  regular  stream  passes  through  the  tap  e  (furnished  with  an 
indicator)  into  the  calorimeter  at  a  temperature  given  by  the  thermometer  x,  and  flows  away 
at  c  at  a  higher  temperature,  shown  by  the  thermometer  y.  When  the  combustion  is  started, 
the  'entry  of  water  is  regulated  by  means  of  e,  so  that  the  thermometers  x  and  y  indicate 
a  temperature  difference  of  10°  to  20° ;  when  the  flow  of  both  gas  and  water  is  constant,  the 
thermometer  y  soon  shows  a  constant  temperature. 

The  gas  is  measured  by  the  meter,  G,  and  then  passes  through  the  regulator,  P,  to  the  bunsen 
burner,  »,  which  is  withdrawn  from  the  calorimeter  to  be  lighted  and  is  then  pushed  in  again 
to  the  height  q  (about  6  in.  up).  If  the  apparatus  is  in  order,  no  water  should  fall  from  d 
into  the  cylinder,  v. 

When  water  is  discharging  from  b  and  from  c,  and  the  thermometric  reading  remains  stationary, 
as  soon  as  the  index  of  the  meter  reaches  the  zero  mark,  or  a  definite  number  of  litres,  the  rubber 
tube  c  is  instantly  placed  from  t  into  V,  which  is  a  graduated  cylinder  placed  quite  close  to  the 
discharge-funnel,  t.  In  the  cylinder  V  is  collected  all  the  water  which  is  discharged  during  the 
combustion  of  a  definite  volume  of  gas  (in  the  proportion  of  100  to  200  litres  of  illuminating  gas 
or  400  to  800  litres  of  suction  gas  or  Dowson  gas  per  hour).  Exactly  at  the  moment  when  the 
meter  indicates  the  volume  of  gas  fixed  upon,  the  rubber  tube  c  is  removed  from  V  to  t.  During 
the  course  of  the  experiment  the  small  variations  in  the  indications  of  the  thermometer  y  are 
noted  at  intervals,  the  mean  temperature  being  subsequently  calculated. 

The  graduated  cylinder,  v ,  contains  the  condensed  water  (a  c.c. )  formed  during  the  combustion 
of  the  gas,  and  this,  in  condensing,  has  given  up  to  the  water  of  the  calorimeter  a  certain  quantity 
of  heat,  which  must  be  subtracted  before  calculating  the  net  calorific  power.  The  gross  calorific 
power,  U,  expressed  in  Calories  per  cubic  metre,  is  calculated  by  means  of  the  formula  : 

A    T   1000 
U  =  '     — ,  where  A  indicates  the  quantity  of  water  in  litres  collected  in  V,  and  Q  the  volume 

of  gas  burned.  If,  for  example,  Q  =  3  litres,  A  =  0-900,  T  =  18°  (that  is,  26-77°,  the  mean  of 
six  readings  of  the  thermometer  y,  less  8-77°  shown  by  the  thermometer  x  to  be  the  temperature 

of  the  water  entering  at  e),  we  have  U  =  —        '  „ —          =  5400  Calories  per  cubic  metre  of 

gas.  In  general  the  calorific  value  is  now  referred  to  1  cu.  metre  of  gas  calculated  at  0°  and 
760  mm.  pressure.  In  cases  where  the  gas  is  used  in  engines  or  other  apparatus  from  which  the 
products  of  combustion  issue  at  a  temperature  above  65°,  the  water-vapour  does  not  condense, 
and  the  gross  calorific  power  (U)  must  be  diminished  by  the  heat  due  to  the  condensation  of  the 
water- vapour  produced  by  the  combustion  of  the  gas  in  the  calorimeter.  From  U  must  hence 
be  subtracted  a  value  obtained  by  multiplying  by  60  the  number  of  c.c.  of  water  condensing  during 
the  combustion  of  Q  litres  of  gas.  This  net  calorific  power,  U1,  is,  for  illuminating  gas,  usually 
10  per  cent,  lower  than  the  gross  calorific  power,  U. 

The  calorific  values  of  different  industrial  gases  are  given  in  Vol.  I.,  p.  489. 


PHOTOMETRY 


63 


1  sq.  metre  of  a  sphere  of  1  metre  radius ;   the  lux  would  be  the  unit  of  illumination,  that 
is,  the  illumination  of  an  area  of  1  sq.  metre  produced  by  1  lumen. 

The  luminous  unit  being  fixed,  different  sources  of  light  and  their  illuminating  powers 
may  be  compared  by  means  of  photometers.^ 

1  Of  these,  the  one  most  largely  used  is  that  of  Bunsen,  which  is  based  on  the  principle  that  the 
intensity  of  light  produced  on  a  definite  surface  by  a  source  of  light  is  inversely  proportional  to  the 
square  of  the  distance.  If  the  distance  between  the  source  of  light  and  the  surface  illuminated  is 
trebled,  the  intensity  of  the  illumination  is  diminished  to  one-ninth  of  its  previous  value.  The 
luminosities  of  two  flames,  /  and  Ilt  which  illuminate  equally  a  given  screen  and  are  at  the  respective 


FIG.  77. 

distances  L  and  Z/from  it,  are  directly  proportional  to  the  squares  of  these  distances  :  I  :I1  = 
Lz  :  LT*,  and  if  1^  is  the  unit  of  measurement,  the  intensity  "of  the  other  source  of  light  will  be  : 

La 

/  —  7--,.    The  Bunsen  photometer  (Fig.  77)  consists  of  a  horizontal  iron  photometer  bench 

i 
3  metres  long  and  divided  decimally  (into  half -centimetres  or  millimetres);  at  one  end  is  placed 

the  comparison  electric  or  candle  lamp  or  the  Carcel  lamp,  the  consumption  of  oil  in  which  is 
regulated  by  a  small  pump  actuated  by  a  clockwork  mechanism,  weighing  on  a  balance  the 
consumption  in  a  given  time  (indicated  by  a  bell) — this  corresponding  with  42  grams  of  oil  per 
hour.  A  screen  of  paper  may  be  moved  backwards  and  forwards  along  the  bench  and  normally 
to  it,  the  middle  of  the  screen  being  rendered  translucent  by  means  of  a  grease-spot  (spermaceti); 


FIG.  78. 


FIG.  79. 


at  the  other  end  of  the  bench  is  placed  the  light  to  be  examined.  When  the  screen  is  equally 
illuminated  on  its  two  faces,  the  grease-spot  is  no  longer  perceptible.  The  intensities  of  the  two 
sources  of  light  are  then  proportional  to  the  squares  of  their  distances  from  the  screen. 

The  measurement  is  made  in  a  dark  room  and,  in  order  to  render  more  evident  the  disappear- 
ance of  the  spot  on  the  two  surfaces,  the  screen  is  placed  between  two  mirrors  arranged  at  an 
angle  (Fig.  78).  An  improvement  on  the  Bunsen  photometer  has  been  made  by  Lummer  and 
Brodhun,  who  substitute  for  the  screen  with  the  grease-spot  a  closed  box,  h  (Fig.  79),  in  which 
are  two  opposite  circular  apertures,  these  illuminating  the  two  faces  of  a  white  screen,/,  by  means 
of  light  from  the  standard  lamp,  and  that  to  be  tested,  placed  at  the  two  extreme  ends  of  the 
photometer  bench.  By  means  of  a  system  of  prisms,  A  B,  the  two  faces  of  the  white  screen 
reflect  the  light  on  to  two  concentric  zones  of  the  field  of  the  eye-piece,  r.  When  the  two  faces 
of  the  screen  are  equally  illuminated,  the  two  zones  of  the  field  also  appear  uniformly  lighted. 


64 


ORGANIC    CHEMISTRY 


COMPARISON  BETWEEN  VARIOUS  SOURCES  OF  LIGHT.  To  produce  the 
luminous  intensity  of  a  Hefner  candle-hour  (HK),  the  following  quantities  of  lighting 
materials  must  be  consumed  : 


Stearine,  first  quality     . 
third     „  . 

Paraffin  wax          ..... 
Two  parts  of  paraffin  wax  and  one  of  stearine 
'Carcel :  colza  oil  .          . 
Petroleum,  flat  wick      .... 

„          round  wick  .... 

Spirit :  incandescent      .... 
v  Petroleum  with  Auer  mantle 
Acetylene  ...... 

[Fish-tail 

;  |     Argand         .          .          .          .          . 

Auer  .          . 

Millenium  (gas  under  pressure) 
^Auer  with  inverted  flame 
f  Arc  lamp  of  small  power 
I    „          „        high       „  ... 

Incandescent  Edison 

Metallic  filament  (osmium,  tantalum) 
[Mercury  vapour  .... 


7-87  grams 

9-58  „ 

6-27  „ 

6-93  „ 

3-99  „ 

2-76  „ 

/2-80  „ 

13-60  „ 

1-90  „ 

0-50  „ 

0-6  litres 

19-0  „ 
10 

1-60  „ 

0-75  „ 

0-70  „ 

1-20  volt-amps. 

0-25 

3-70 

1-90 

0-50 


It  is  easy  to  calculate  the  cost  from  the  prices  of  the  various  methods  of  lighting,  these 
varying  from  town  to  town  and  from  country  to  country.  In  1896  Lupke  calculated  the 
following  numbers  of  normal  candle-hours  to  be  obtainable  for  one  mark  (one  shilling), 
the  calculation  being  valid  only  for  that  period  and  for  Germany  :  wax,  33 ;  stearine,  77 ; 
colza  oil,  150;  electric  lamp  with  incandescent  carbon  filament,  150;  fish-tail  gas-jet,  625; 
acetylene  and  air  with  an  edged  burner,  716;  oil -gas,  1660;  water-gas  with  benzene,  1666; 
electric  arc  lamp,  2232 ;  Auer  gas  lamp,  2300 ;  Auer  water-gas  lamp,  4350. 

From  gas  at  l-Qd.  (0-2  lira)  per  cubic  metre,  as  a  source  of  heat,  1000  Cals.  are  obtained 
for  0-38d.  (0-04  lira),  whilst,  using  electric  current  at  3-07d.  (0-32  lira)  per  kilowatt-hour, 
1000  Cals.  would  cost  about  3-65d.  (0-38  lira).  For  power  purposes,  the  electric  current 
[at  2-4d.  (0-25  lira)  per  kilowatt-hour]  costs  more  than  double  as  much  as  gas  [at  1-73^. 
(0-18  lira)  per  cubic  metre]. 

During  the  past  few  years  a  considerable  advance  has  been  made  by  the  use  of  incan- 
descent electric  lamps  with  metallic  filaments  (tantalum,  tungsten,  osmium,  etc.),  which 
reduce  the  consumption  of  electrical  energy  by  one-half,  but  at  the  same  time  gas  lamps 
have  been  improved  by  the  use  of  high-pressure  gas,  and  those  with  inverted  flames  are 
still  decidedly  more  economical  than  metallic  filament  electric  lamps.  From  the  hygienic 
point  of  view  the  disadvantages  of  gas  lighting  have  been  exaggerated,  as  it  has  not  been 
realised  that  the  use  of  gas  causes  circulation  and  renewal  of  the  air,  and  that  the  pro- 
duction of  water- vapour  and  carbon  dioxide  are  negligible  compared  with  the  similar  effects 
produced  by  the  respiration  of  human  beings. 


OIL-GAS 

In  cases  where  the  installation  of  a  plant  for  the  carbonisation  of  coal  would  be  inex- 
pedient, owing  to  the  small  consumption  of  illuminating  gas,  it  may  be  convenient  to 
prepare  oil-gas  by  dropping  into  a  red-hot  retort  (see  later,  "  Cracking  "  Process  in  the  Petro- 
leum Industry)  fatty  residues,  lignite,  tar  oils,  resins,  and  medium  petroleum  oils  (blown 
oil,  see  Petroleum).  This  destruction  by  heat  (at  745°  to  790°)  produces  a  gas  which 
consists  mainly  of  C2H4  and  H2,  and  when  compressed  at  10  to  12  atmos.,  to  separate  part 
of  the  heavy,  liquid  hydrocarbons  (with  slight  loss  of  calorific  value),  and  enriched  with 
25  per  cent,  of  acetylene,  is  used  for  the  illumination  of  railway  carriages.  Oil-gas  may 
also  be  prepared  easily  and  abundantly  by  dropping  oil  into  gas-producers  containing  red-hot 
coke. 


PETROLEUM  65 

Davis  (1910)  avoids  the  formation  of  tar  by  pulverising  the  oil  in  the  retort  by  means 
of  air  instead  of  steam.  In  this  way  a  gas  is  obtained  having  the  following  percentage 
composition:  CO2,  2;  heavy  hydrocarbons,  26;  CO,  1-5;  CH4,  35;  H2,  5-5;  and  N,  30. 
Injection  of  oil-gas  (two-thirds)  and  water-gas  (one-third)  into  a  coke  gas-producer  yields 
a  gas  containing  46-5  per  cent,  of  H2,  31-3  of  CH4,  7  of  N2,  11-6  of  heavy  hydrocarbons, 
and  2-8  of  CO,  its  calorific  value  being  5490  Cals. 

As  early  as  1815  public  lighting  with  oil-gas  was  attempted  (Liverpool  used  it  for  some 
years),  but  it  was  only  after  1860-1870  that  this  industry  assumed  importance.  From 
100  kilos  of  lignite  paraffin  oil  are  obtained  60  cu.  metres  of  gas,  and  with  a  consumption 
of  35  litres  of  the  gas  per  hour,  7-5  normal  candles  (German)  are  obtained;  its  illuminating 
power  is  four  times  as  great  as  that  of  ordinary  lighting  gas.  One  kilo  of  medium  petroleum 
oil  gives  600  litres  of  gas,  300  to  400  grams  of  tar,  and  40  to  60  grams  of  coke.  If  a  greater 
yield  of  the  gas  is  obtained,  it  loses  in  illuminating  power.  The  purification  of  oil-gas  is 
carried  out  in  practically  the  same  way  as  that  of  coal-gas.  Mineral  oil  for  gas  and  for 
engines  is  produced  in  large  quantities  in  Galicia,  where  it  is  sold  for  less  than  19-5'i.  per 
cwt.  (4  lire  per  quintal);  Germany  alone  imported  30,000  tons  of  it  in  1909. 


PETROLEUM    INDUSTRY 

Crude  petroleum  also  goes  under  the  name  of  mineral  oil  or  naphtha,  and 
is  a  more  or  less  dark  liquid  (according  to  its  origin)  with  a  peculiar, 
pronounced  odour.  It  is  found  in  various  parts  of  the  earth  in  the  strata  of 
the  tertiary  epoch  and  also  of  preceding  epochs.  The  principal  centres  of 
production  are  Baku  (Russia)  and  the  United  States.1 

1  History  of  the  Petroleum  Industry.  The  use  of  petroleum  and  of  tar  goes  back  to  the 
earliest  historical  times  (the  Biblical  legend  relates  that  Noah  rendered  his  ark  impermeable 
by  means  of  tar,  and  in  the  construction  of  the  Tower  of  Babel  a  mortar  was  used  prepared 
with  naphtha  !(?)).  Certain  races  then  employed  naphtha  as  a  fuel,  and  the  Egyptians  made 
use  of  it  in  the  preparation  of  mummies. 

In  small  quantities  petroleum  is  found  in  nearly  all  countries,  but  95  per  cent,  of  the  total 
production  is  given  by  North  America  and  Russia.  Two  centuries  before  petroleum  was  used 
in  America  that  from  Parma  in  the  Apennines  was  used  for  lighting,  e.  g.,  at  Genoa,  Parma,  etc. 
The  most  important  petroleum  wells  now  in  Italy  are  in  the  Province  of  Piacenza  (at  Fiorenzuola 
d'Arda)  and  at  Salsomaggiore,  Borgo  S.  Donnino,  and  Montechino;  less  important  deposits 
are  found  also  in  Calabria.  At  Velleia  the  industry  has  been  worked  for  many  years  by  a  French 
company,  many  wells  200  to  450  metres  deep  having  been  sunk  along  the  right  bank  of  the  Chero ; 
this  company  was  absorbed  by  an  Italian  syndicate  in  1907. 

In  Austria  the  region  richest  in  petroleum  is  Galicia.  In  1895,  when  a  well  300  metres  deep 
was  bored,  a  fountain  was  formed  which,  in  thirty-six  hours,  yielded  5000  barrels  of  petroleum 
(1  barrel  =  42  gallons  =  159  litres  =  145  kilos).  Still  more  important  wells  in  other  countries 
are  mentioned  on  p.  74. 

In  Russia  the  most  important  sources  of  petroleum  are  found  in  the  province  of  Baku  (99  per 
cent,  of  the  whole  production  is  obtained  from  an  area  of  6  sq.  kilos),  and  partly  at  Grosnv  to 
the  north.  From  the  most  remote  times,  before  Christ,  sacred  fires,  fed  by  petroleum  and  by  the 
inflammable  gases  liberated  from  it,  have  been  kept  burning  uninterruptedly  in  the  temples 
(down  to  1880 ).  During  his  voyage  in  the  thirteenth  century  Marco  Polo  visited  these  marvellous 
springs  of  "  oil  not  good  to  use  with  food  but  good  to  burn  and  also  used  to  anoint  camels  that  have 
the  mange." 

In  1820  the  Baku  petroleum  wells  were  declared  the  property  of  the  Russian  State  and  the 
Government  made  concessions  to  contractors,  who  worked  them  in  a  primitive  manner  until 
1872.  In  1873,  the  most  important  wells  and  petroleum -bearing  lands  were  put  up  for  auction 
by  the  Government,  who  levied  a  tax  on  the  petroleum  extracted.  This  condition  of  affairs  was 
less  favourable  than  that  holding  in  the  American  industry,  so  that  in  1877  the  tax  was  repealed 
and  the  Russian  petroleum  industry,  passing  into  the  hands  of  great  capitalists  (Nobel  Roths- 
child, etc.),  underwent  extraordinary  development  and  often  competes  advantageously  w'ith  that 
of  America. 

The  first  plant  installed  by  Baron  Thormann  for.  the  distillation  of  petroleum  was  constructed 
at  Baku  in  1858  according  to  suggestions  and  plans  furnished  by  Liebig,  carried  out  by  one  of 
his  assistants  (Moldenhauer),  and  improved  by  Eichler.  The  first  wells  bored  on  the  American 
system  date  from  1869.  Before  1870,  the  production  was  only  250,000  poods  (1  pood  =  16-38 
kilos),  but  in  1872  it  reached  1,500,000  poods,  and  then  grew  with  astounding  rapidity  (see  later 
Statistics ). 

There  are  also  important  petroleum  deposits  in  Japan,  but  the  production  is  still  limited  : 

VOL.  n.  5 


66  ORGANIC    CHEMISTRY 

In  some  places  it  overflows  at  the  surface  of  the  earth  through  porous 
rocks  or  clefts ;  in  others  it  is  found  accumulated  under  pressure  in  large 
cavities  or  pockets,  since,  when  it  is  reached  by  borings  or  wells,  powerful  jets 
rise  above  the  surface  of  the  earth  often  to  the  height  of  100  metres,  thus 
forming  fountains  of  petroleum  which  last  from  a  few  weeks  up  to  seven  or 
eight  months,  and  throw  up  also  large  quantities  of  inflammable  gases  and 
sand. 

Some  petroleum  deposits  have  been  gradually  evaporated  and  oxidised 

in  1874  it  amounted  to  126,150  kwan  (1  kwan  =  3-78  kilos),  in  1884  to  1,400,000  kwan,  and  in 
1903  to  about  126,000  tons. 

During  recent  times  important  sources  of  petroleum  have  also  been  discovered  in  Canada. 

In  Great  Britain,  Young  commenced  in  1848  the  industrial  treatment  of  a  species  of  petroleum 
discovered  in  a  coal-mine  at  Alfreton ;  this  was  subjected  to  distillation  to  obtain  lamp  oil, 
lubricating  oil,  and  a  small  proportion  of  paraffin  wax,  from  which  candles  were  made.  Subse- 
quently he  distilled  bituminous  shale  (see  later),  the  oils  obtained  being  refined  by  means  of 
sulphuric  acid  and  soda.  In  1859  refining  of  petroleum  by  the  Young  system  was  started 
in  America. 

The  greatest  impulse  to  the  petroleum  industry  has  come  from  the  United  States,  where 
important  deposits  of  petroleum  have  been  found,  first  in  the  State  of  Pennsylvania  (in  a  strip  of 
land  about  100  kilometres  long  the  production  of  petroleum  increased  from  3180  hectolitres  in  1859 
to  16,000,000  hectolitres  in  1874,  the  price  per  barrel  falling  during  the  same  period  from  100  lire, 
or  £4,  to  6-5  lire,  or  5s.  2\d. ;  these  deposits  are  now  apparently  becoming  exhausted),  and  then 
in  Virginia,  Ohio,  Indiana,  California,  Louisiana,  and  Tex?,s.  At  the  present  time  the  most 
important  sources  of  petroleum  in  the  United  States  are  in  the  Washington  district  and  in 
California. 

The  first  studies  on  petroleum  in  America  were  made  by  Silliman  in  1854,  by  fractional 
distillation,  and  these  were  followed  by  unsuccessful  industrial  efforts  caused  by  the  low 
production  of  the  wells  utilised  and  by  many  commercial  difficulties,  which  were  overcome  by 
L.  Drake  in  1859  by  the  use  of  artesian  wells. 

The  first  petroleum  well  in  America  was  obtained  by  pure  chance ;  at  Titusville  in  Pennsyl- 
vania a  well  was  being  sunk  for  drinking  water,  and  when  a  depth  of  22  metres  was  reached,  a 
continuous  jet  of  petroleum  appeared,  yielding  4000  litres  of  naphtha  per  day. 

Just  as  America  was  taken  with  the  "  gold-fever  "  after  the  discovery  of  gold  in  California, 
so  the  United  States  caught  the  petroleum  fever.  Pennsylvania  was  invaded  by  adventurers, 
and  borings  were  made  wherever  the  geological  formation  of  the  earth  admitted  of  it;  all 
had  faith  in  the  goddess  Fortune,  who,  as  always,  favoured  some  and  drove  others  to  ruin 
and  despair.  In  1861  the  number  of  derricks  (used  for  boring)  exceeded  2000.  The  work 
was  carried  out  hastily  and  without  thought,  usually  empirically,  the  idea  being  to  succeed 
first.  Much  petroleum  was  lost,  and  much  was  burnt,  causing  immense  losses  and  ruin  to 
numerous  firms. 

Great  capitalist  companies  were  then  formed,  and  these  studied  calmly  and  rationally  the 
technical  and  commercial  problem,  and  very  soon  created  an  enormous  industry,  which  rapidly 
brought  petroleum  into  common  use  all  over  the  world.  Ships  and  railways  and  then  iron  pipes 
tens  and  hundreds  of  kilometres  in  length  served  to  transport  the  petroleum  rapidly,  continuously, 
and  economically  from  the  wells  to  the  refineries,  and  from  these  to  the  seaports,  where  it  was 
shipped  to  the  merchants. 

In  America  to-day  petroleum  is  monopolised  by  huge  "  trusts,"  especially  the  Vacuum  Oil 
Company  and  the  Standard  Oil  Company  of  New  Jersey,  to  which  are  affiliated  seventy  companies 
with  a  total  capital  of  £18,000,000  and  employing  60,000  workmen  and  monopolising  about 
60  per  cent,  of  American  petroleum.  The  Standard  Oil  Company,  founded  in  1872,  paid  in 
dividends  from  1882  to  1892  a  total  of  £94,400,000,  and  from  1894  to  1903  paid  to  its  shareholders 
dividends  of  33  to  48  per  cent.  !  In  1906  President  Roosevelt,  under  pressure  of  public  opinion, 
waged  war  against  this  colossal  trust  by  rupturing  the  connection  between  the  steel  ring  and  the 
interests  bound  up  with  it  and  making  them  liable  to  a  fine  of  over  £6,000,000.  In  consequence 
of  this  commercial  war  of  1906  the  Standard  Oil  Company  lost  £25,000,000,  of  which  £12,900,OCO 
fell  on  Rockefeller,  the  well-known  millionaire  president  of  the  company.  The  sentence  was 
then  annulled  on  appeal,  but  the  result  was  that  the  company  fought  its  competitors  by  lowering 
prices  [petroleum  that  previously  cost  30  centesimi  (2-Qd.)  per  litre  has  been  lowered  in  price 
during  the  last  few  years  to  15  centesimi  (l-45rf.)  ],  and  in  1908  made  a  net  profit  of  £16,000,000, 
and  proposed  raising  its  capital  to  £100,000,000.  This  explains  how  Rockefeller  has  been  able, 
without  any  great  sacrifice,  to  make  benefactions  of  so  many  millions  during  the  past  few  years, 
e  ipecially  for  the  extension  of  university  study  in  America.  The  sentence  of  the  Supreme  Court 
of  Washington  (March  15,  1911)  gave  judgment  against  the  Standard  Oil  Company,  for  con- 
travention of  the  law  against  trusts,  and  ordered  dissolution  of  this  powerful  company  within 
six  months. 

In  1912  the  Standard  Oil  Company  was  indeed  split  up  into  numerous  branches  which,  however, 
acquire  most  of  the  crude  American  petroleum  and  refine  it  in  numerous  works.  The  most 
important  of  these  is  the  Ba  yonne  refinery,  New  Jersey,  which  distils  daily  40,000  barrels  of  crude 
petroleum  to  obtain  benzine,  lamp  oil,  intermediate  and  heavy  oils,  paraffin  wax,  etc. 


ORIGIN     OF     PETROLEUM  67 

during  the  lapse  of  ages,  leaving  a  black  deposit  of  mineral  tar,  asphalte,  or 
bitumen  (see  section  on  Paraffin  Wax). 

ORIGIN  OF  PETROLEUM.  Vaiious  hypotheses  have  been  put  forward  to  explain 
the  origin  of  petroleum,  and  even  to-day  opinions  are  divided,  probably  owing  to  the 
fact  that  petroleum  has  not  one  single  origin,  since,  in  different  parts  of  the  earth's  crust, 
it  has  different  qualities  and  compositions  (see  below). 

(1)  Hypothesis  of  Inorganic  Origin.  A.  v.  Humboldt  supposed  petroleum  to  have 
originated  from  inorganic  gaseous  products  under  the  influence  of  volcanic  forces,  and  in 
1866  Berthelot  advanced  the  hypothesis  that,  by  the  action  of  carbon  dioxide  on  alkali 
metals  inside  the  earth's  crust,  acetylides  would  be  formed  which  with  hydrogen  would 
give  acetylene  derivatives,  these  then  undergoing  various  condensations  to  form  petroleum 
and  tar.  Byasson  in  1871  explained  the  formation  of  the  hydrocarbons  of  petroleum  as 
due  to  the  action  of  H2S,  C02,  and  water-vapour  on  layers  of  red-hot  iron,  this  action 
.being  produced  by  the  infiltration  of  sea- water,  through  clefts  at  the  bottom  of  the  ocean, 
in  such  a  way  that,  together  with  calcareous  matter,  it  was  brought  into  contact  with 
deposits  of  heated  iron  or  iron  sulphide.  Mendeleev  (1877)  regarded  the  hydrocarbons 
of  petroleum  as  originating  in  the  igneous  strata  of  the  earth's  crust  by  the  action  of  aqueous 
infiltrations  on  pre-existing  deposits  of  carbide  of  iron  or  other  metallic  carbides.  Hahn 
(1864)  and  Cloez  (1874-1879)  obtained  support  for  Mendeleev's  hypothesis  by  showing 
experimentally  that  saturated  hydrocarbons  and  a  few  olefines  (which  polymerise  under 
the  action  of  pressure  and  heat)  are  formed  when  cast-iron  or  spiegeleisen  (substances  which 
contain  carbide  of  iron)  is  dissolved  in  dilute  acid.  In  1891  Ross  brought  forward  again 
and  modified  Byasson's  hypothesis;  he  assumed  that  volcanic  gases,  especially  H2S  and 
SO2,  in  contact  with  heated  chalky  rocks,  would  form  gypsum,  with  separation  of  sulphur 
and  production  of  saturated  and  unsaturated  hydrocarbons  (this  would  give  also  an  explana- 
tion of  the  origin  of  sulphur,  yet  in  Sicily,  where  sulphur  abounds,  no  petroleum  is 
found  !). 

These  various  hypotheses  on  the  inorganic  origin  of  petroleum  assume  the  formation 
of  the  latter  in  igneous  primitive  (archaic)  geological  strata,  where  the  presence  of  organic 
compounds  is  excluded,  the  petroleum  then  finding  its  way  to  the  higher  layers  of  the 
earth's  crust  by  seismic  convulsions.  It  is,  however,  precisely  these  older  archaic  strata, 
deprived  of  water  and  of  organic  substances,  which  give  no  trace  of  petroleum.  On  the 
other  hand,  if  the  petroleum  were  formed  in  very  hot  strata,  it  should  issue  from  the  borings 
at  a  moderately  high  temperature,  and  there  should  have  been  separation  of  the  light 
petroleum  (more  volatile)  and  the  heavy  into  distinct  layers.  This  is  not  actually 
the  case. 

However,  during  recent  years  this  hypothesis  has  again  come  into  favour,  owing  to 
the  interesting  work  of  Moissan  (1894-1896)  on  the  formation  of  saturated  hydrocarbons 
by  the  action  of  water  on  aluminium  carbide  (see  p.  35),  and  that  of  Sabatier  and  Senderens 
(1896-1902),  who  showed  experimentally  that,  in  presence  of  catalytic  nickel  (obtained  by 
reduction  of  the  oxide  with  hydrogen  at  300°),  hydrogen  and  unsaturated  hydrocarbons 
(ethylene,  acetylene,  etc. )  give  rise  to  saturated  hydrocarbons  such  as  occur  in  petroleum 
(p.  35).  Even  these  syntheses,  however,  do  not  yield  very  high  and  solid  hydrocarbons 
like  those  present  in  crude  petroleum,  although  recently  (1908-1909)  A.  Brun,  Stieger, 
and  Becker  showed  that  hydrocarbons  similar  to  paraffin  wax  are  formed  by  the  interaction 
in  the  hot  of  iron  carbide  and  ammonium  chloride,  even  in  absence  of  water. 

(2)  Hypothesis  of  the  Vegetable  Origin  of  Petroleum.  This  was  enunciated  at  intervals 
by  Binney  (by  distillation  of  peat),  by  Kobell  (by  distillation  of  coal),  and  by  Bischof, 
who  considered  petroleum  to  be  formed  by  the  action  of  sea- water  on  cellulose  and  on 
coal  included  in  the  geological  strata  of  the  earth's  crust.  This  hypothesis  of  the  vegetable 
origin  was  later  supported  or  attacked  by  various  writers,  and  to  the  fact  that,  in  general, 
carboniferous  strata  do  not  contain  petroleum,  is  opposed  the  discovery  of  small  deposits 
of  petroleum  in  the  coal-seams  near  Wombridge  and  of  certain  petroliferous  substances 
in  some  Japanese  coals ;  Heifer  showed,  however,  in  the  first  case,  that  the  neighbourhood 
of  bituminous  schists,  rich  in  the  remains  of  fishes,  could  not  be  excluded,  and,  if  it  is 
desired  to  explain  the  formation  of  petroleum  from  marine  vegetable  organisms,  it  is  not 
possible  to  conceive  of  a  sufficient  quantity  of  these  to  give  rise  to  the  immense  amounts 
of  petroleum  now  discovered.  Further,  other  more  recent  geological  investigations  would 


68  ORGANIC    CHEMISTRY 

exclude  the  vegetable  origin  of  petroleum,  although  the  most  recent  chemical  work  tends 
to  render  such  origin  highly  probable.  It  is,  indeed,  found  that  petroleum  rotates  the 
plane  of  polarisation  of  light  to  the  right  (see  later),  as  do  most  optically  active  vegetable 
substances,  whilst  substances  of  animal  origin  rotate  it  preferably  to  the  left.  Engler, 
however,  states  that  this  observation  is  not"  very  conclusive,  since  these  active  substances 
may  be  due  to  the  condensation  of  unsaturated  products  originating  in  the  decomposition 
of  the  prime  materials  (animals  or  possibly  vegetables).  Kramer  and  Potonie  (1906-1907) 
,  point  out  that  all  petroleums  (also  certain  lignites  and  ozokerite)  contain  algce  wax,  from 
which,  by  various  reactions  and  decompositions,  it  is  easy  to  pass  to  substances  like  petro- 
leum ;  and  simple  substances,  by  polymerisation  (by  heat  and  pressure),  form  more  complex 
tarry  substances,  etc. ;  the  presence  of  wax  demonstrates  that  petroleum  is  formed  not 
in  the  hot  by  distillation,  but  rather  in  the  cold  and  at  high  pressures.  The  prime  material 
of  petroleum  would  hence  probably  be  the  enormous  formation  of  algce  which  have  been 
produced  at  all  epochs  and  are  to-day  accumulating  in  marshy  places.  These,  during 
thousands  of  centuries  and  under  the  action  of  pressure  and  heat,  could  undergo  the  same 
transformations  and  putrefactions  (mixed  sometimes  with  animal  remains),  leaving  the 
wax  for  the  formation  of  petroleum;  so  that  petroleum  would  be  formed  in  all  epochs 
and  is  perhaps  being  formed  now  !  The  varying  composition  of  petroleum  would  be  due, 
according  to  Kramer,  to  filtration  through  various  geological  strata,  which  would  have 
removed  greater  or  less  quantities  of  bituminous  products  so  as  to  produce  pale,  light 
petroleums  like  those  of  Velleia  and  Montechino.  Hence  the  greater  or  less  content 
of  tarry  substances  cannot  serve  as  an  indication  of  the  epoch  of  formation  of  a 
petroleum,  since  part  of  these  substances  may  have  been  lost  during  the  geological 
nitrations. 

(3)  Hypothesis  of  the  Animal  Origin  of  Petroleum.  This  was  enunciated  and  vigorously 
upheld  by  Heifer,  and  supported  and  supplemented  by  Ochsenius  (1892),  Zaloziecki  (1892), 
Veith,  Dieckhoff  (1893),  Aisinmann  (1894),  Heusler  (1896),  Holde  (1897),  Aschan  (1902), 
and  Zuber  (1897,  who  supported  only  the  organic  origin),  and  more  especially  and  most 
exhaustively  by  Engler  (1888-1912). 

This  hypothesis  supposes  that  great  layers  of  various  fishes  and  molluscs,  formed  on 
the  ocean-bed  during  past  geological  epochs,  gradually  underwent  decomposition,  first 
losing  the  nitrogenous  components  (albuminoids)  as  gaseous  or  soluble  compounds,  the 
remaining  fats  being  slowly  transformed  partially  into  bituminous  substances.  These, 
together  with  the  residual  fats,  under  the  action  of  great  pressure  and  heat  (developed, 
in  part,  by  these  decompositions)  would  yield  glycerol,  which  would  generate  acrole'in 
and  then  aromatic  hydrocarbons,  while  the  remaining  fatty  acids  (by  the  action  of  hydrogen 
formed  in  all  these  decompositions)  would  give  rise  to  the  various  saturated  hydrocarbons 
constituting  petroleum,  CO2  being  liberated. 

The  animal  origin  hypothesis  is  also  supported  by  the  observation  of  Fraas, 
that  petroleum  issues  from  the  coralliferous  banks  of  the  Red  Sea,  and  by  the  odour 
of  petroleum  exhibited  by  certain  phosphorites  which  are  undoubtedly  of  animal 
origin. 

The  objection  has  been  raised  that,  if  petroleum  were  of  animal  origin,  it  should  contain 
nitrogenous  compounds.  Although  this  is  not  necessary,  yet  the  presence  of  nitrogen 
products  (ammonia  and  pyridine  bases,  free  nitrogen  and  ammonium  carbonate)  has 
been  shown  in  petroleum  and  in  gases  emanating  from  the  earth.  Texas  petroleum  contains 
up  to  1  per  cent,  of  nitrogen. 

Engler  showed  experimentally  that,  under  certain  conditions,  animal  fats  may  be 
transformed  into  olefines  or  analogous  products  in  the  laboratory  (by  distilling  fish-oil 
under  4  to  10  atmos.  pressure).  In  1909,  Engler,  Routala,  Aschan.  and  others  effected  the 
laboratory  production  of  naphthenes,  paraffins,  and  heavy  mineral  oils,  by  heating  amylene 
and  hexylene  under  pressure  and  in  presence  or  absence  of  aluminium  chloride  as 
catalyst. 

Many  facts  support  the  view  that  the  petroleum  of  the  geological  strata  studied  has 
been  formed  at  a  low  temperature  and  by  slow  but  continuous  reactions  lasting  for  thousands 
of  years. 

To  the  doubt  that  may  be  raised  as  to  the  enormous  quantity  of  animal  remains  neces- 
sary to  explain  the  large  amounts  of  petroleum  being  raised  at  the  present  time,  it  may 
be  answered  that  if  the  annual  catch  of  herrings  on  the  coasts  of  the  northern  seas  and  that 


ORIGIN     OF     PETROLEUM  69 

of  sardines  by  French  fishermen  were  to  accumulate  on  the  ocean-bed  for  2000  years,  it 
would  be  quite  sufficient  to  explain  the  petroleum  production  of  Russia.1 

It  would,  however,  be  necessary,  for  the  preservation  of  this  enormous  cemetery  of 
fish,  that  the  corpses  should  not  be  eaten  by  other  larger  fish;  the  conditions  must  then 
be  such  that  fish  approaching  the  cemetery  are  killed.  This  is  highly  probable,  as  the 
existence  of  such  conditions  at  the  bottom  of  the  Black  Sea  has  recently  been  proved. 
In  fact,  below  a  certain  depth,  there  is  so  much  dissolved  hydrogen  sulphide  that  any 
animal  is  instantly  poisoned  there,  its  body  going  to  swell  the  vast  numbers  that  have 
preceded  it  at  the  bottom. 

With  these  proofs  is  connected  the  most  recent  and  most  rational  interpretation  of  the 
origin  of  petroleum.  It  is  supposed  that  the  decomposition  of  the  residual  animal  fats 
is  aided  by  certain  ferments  as  yet  not  studied — anaerobic  bacteria  analogous  to  those 
which  have  been  studied  in  the  cases  of  the  transformation  of  wood  into  coal,  the  fermenta- 
tion of  cellulose,  peat,  etc. ;  the  hydrogen  sulphide  formed  at  the  bottom  of  the  sea  would 
be  a  product  of  the  fermentations  due  to  these  bacteria. 

Walden  (1910)  and  Rakusin  (1905  and  1906)  made  a  new  contribution  to  the  explanation 
of  the  origin  of  petroleum,  by  discovering  in  various  petroleums  a  slight  optical  activity, 
undoubtedly  due  to  substances  of  organic  origin  (animal  or  vegetable).  Neuberg  (1905- 
1907)  has  shown  that,  in  the  putrefaction  of  protein  substances  (due,  according  to  Effront, 
to  the  action  of  proteolytic  enzymes  generated,  together  with  amidases,  by  micro-organisms, 
see  later,  Alcohol  and  Enzymes),  marked  quantities  of  optically  active  acids  and  amino- 
acids  are  formed,  and  by  heating  under  pressure  or  dry-distilling  a  mixture  of  oleic  acid 
with  a  little  valeric  acid,  a  product  is  obtained  which,  after  purification,  has  the  characters 
of  naphtha  as  regards  the  optical  rotation,  boiling-point,  and  other  properties.  All  this 
supports  the  organic — probably  animal — origin  of  petroleum,  and  even  if  the  fats  do  not 
give  an  optically  active  petroleum,  the  activity  would  be  imparted  by  the  decomposition 
products  of  the  proteins.  The  optical  activity  of  petroleum  was  recognised  as  far  back  as 
1835  by  Biot,  who,  however,  drew  no  practical  or  theoretical  conclusions  from  the  observa- 
tion. Rakusin  observed  that  petroleums  exhibit  the  Tyndall  phenomenon  (Vol.  I.,  p.  107) 
to  a  more  or  less  marked  extent,  and  since  petroleums  are  sometimes  inactive  and  have 
varying  chemical  composition,  he  regards  the  different  hypotheses  concerning  their  origin  as 
justified.  Petroleum,  as  a  liquid,  must  be  considered  as  intermediate  to  natural  inflam- 
mable gas  and  solid  asphalte  or  ozokerite.  Since  the  white  cerasin  which  is  extracted 
from  ozokerite  is  dextro-rotatory,  it  must  be  concluded  that  ozokerite  is  of  organic  origin 
(the  products  formed  by  synthesis  from  simpler  or  artificial  substances  being  optically 
inactive,  see  p.  23). 

The  petroleum  or  similar  substances  prepared  artificially  from  the  elements  possess  all 
the  properties  of  true  petroleum,  but  are  optically  inactive.  Hence  the  most  certain 
criterion  of  the  organic  origin  of  a  petroleum  is  its  optical  rotation.  If  a  petroleum  is 

1  Fishing  Industry.  The  following  statistics  represent  the  mean  annual  figures  for  the 
period  1908-1914,  and  refer  to  both  sea  and  fresh-water  fishing  : 

Number  of  fishing  vessels.. 

, ,.  Number  of  Value  of  fish 

Steam.                     Sailing.  fishermen.  caught  (£). 

Great  Britain                                    2,200                     —  106,000  11,800,000 


France 
Norway    . 
Spain 
Germany 
Holland    . 
Denmark 
Italy 
United  States 


170  26,000  96,000  4,600,000 

175  —  100,000  3,120,000 

320  22,500  121,000  3,000,000 

308  15,000  29,800  3,320,000 

80  5,300  21,000  1,800,000 

160  1,000  14,000  640,000 

25,796  110,000  1,360,000 

4,899  83,800  219,000  12,000,000 


To  obtain  an  idea  of  the  fertility  of  certain  fish,  the  shad,  a  fish  of  the  herring  family,  weighing 
up  to  5  to  6  kilos,  may  be  considered ;  the  female  lays  as  many  as  100,000  eggs,  which  may  be 
fertilised  artificially,  as  is  done  with  the  salmon  and  trout.  In  North  America  the  eggs  are 
collected  and  despatched  to  the  Central  Pisciculture  Station  at  Washington,  where  "they  are 
hatched  in  four  days  in  Macdonald  or  Weiss  tanks  with  flowing  water  at  18°  to  19°,  and  are 
immediately  placed  in  the  rivers,  where  they  grow  rapidly.  Every  year  more  than  100,000,000 
eggs  are  fertilised  in  this  way  and  from  1875  to  1890  the  shad  fishing  showed  an  increase  of  100 
per  cent.,  corresponding  with  £160,000.  The  female  cod  may  lay  as  many  as  6,000,000  eggs 
during  its  lifetime,  and  the  turbot  even  9,000,000 ;  an  adult  eel  contains  10,000,000  to  12,000,000 


70  ORGANIC    CHEMISTRY 

optically  inactive,  it  may  have  originated  from  a  racemic  product  (optically  and  transitorily 
inactive,  see  p.  21 )  of  organic  origin,  but  may  have  been  formed  from  inorganic  materials. 
However,  inactive  petroleums  are  rare;  Rakusin  (1907)  has  found  only  three  such  up 
to  the  present,  one  Russian  (Surakhany)  and  two  Italian  (Montechino  and  Velleia),  and 
he  states  that  not  only  the  degree  of  carbonisation  of  the  petroleum  (richness  in  carbon), 
but  also  its  degree  of  racemisation  must  be  taken  into  account  in  judging  its  geological  age. 
In  1908,  Zaloziecki  and  Klarfeld  held  that  the  optical  activity  of  petroleum  is  due  to 
the  presence  of  terpenes  or  colophony,  but  Neuberg  regards  it  as  due  to  decomposition 
products  of  amino-acids  (valeric  or  isocaproic  acid)  formed  from  the  proteins.  Marcusson 
(1908)  combats  the  last  two  hypotheses,  and  shows  that  it  is  more  probable  that  the 
activity  is  derived  from  decomposition  products  (dextro-rotatory)  of  laivo-rotatory 
cholesterols  (and  hence  of  animal  origin,  whilst  the  vegetable  ones  are  dextro-rotatory 
and  yield  laevo-rotatory  decomposition  products).  By  distilling  olein  under  pressure, 
Marcusson  (1910)  obtained  hydrocarbons  which  had  an  optical  activity  equal  to  that  of 
natural  petroleums  and  which  he  regarded  as  formed  from  the  original  cholesterols.  By 
the  action  of  ozone,  Molinari  and  Fenaroli  (1908)  showed  that  the  Russian  and  Roumanian 
petroleums  examined  by  them  contained  no  unaltered  cholesterol,  but  this  does  not  exclude 
the  presence  of  active  decomposition  products,  which,  however,  would  not  contain  double 
linkings.  C.  Engler  and  Bobrzynski  (1910)  confirmed  these  results.  In  addition  to 
dextro-rotatory  compounds,  Java  and  Borneo  petroleums  contain  Isevo-rotatory  substances 
which  become  dextro-rotatory  at  350°  (as  happens  when  Isevo-rotatory  cholesterol  is  heated) ; 
also  certain  inactive  fractions  become  dextro-rotatory  when  heated.  Rakusin,  Molinari, 
and  Fenaroli  showed  that  the  optical  activity  increases  in  those  portions  of  petroleum 
that  have  the  highest  boiling-point.  Charitschkov  (1912)  supposes  petroleum  to  be 
derived  from  asphalte. 

COMPOSITION  AND  PROPERTIES  OF  CRUDE  PETROLEUM.  As 
obtained  from  the  wells,  crude  petroleum  varies  in  colour  from  yellowish 
to  pale  brown,  or  even  black,  according  to  its  origin;  it  exhibits  a  marked 
greenish  fluorescence  and  a  characteristic,  garlic-like  odour.  The  dissolved 
gas  soon  separates  spontaneously,  and  sometimes,  on  oxidation  in  the  air, 
petroleum  deposits  dark,  bituminous  substances  (paraffin  wax,  tar).  The 
lighter  petroleums  are  the  paler  and  have  an  agreeable,  ethereal  odour,  whilst 
the  heavier  ones  are  darker  and  have  an  unpleasant  odour. 

Certain  petroleums  have  recently  been  found  to  be  radioactive. 

The  presence  of  sulphur  in  petroleum,  even  if  much  less  than  1  per  cent., 
injuriously  affects  its  odour  and  colour.  The  specific  gravity  of  petroleum 
varies  from  0'780  to  0'970.  Petroleum  obtained  from  Terra  di  Lavoro,  Italy, 
has  a  high  specific  gravity  (0*970)  and  certain  Roumanian  and  Indian  petroleums, 
rich  in  paraffin  wax,  show  values  higher  even  than  this,  sometimes  as  much 
as  1-3. 

Petroleum  is  soluble  in  ether,  benzene,  chloroform,  and,  to  some  extent, 
in  amyl  alcohol;  it  dissolves  only  slightly  in  ethyl  alcohol  and  not  at  all  in 
water. 

The  specific  heat  varies  from  0'4625  to  0'4724,  that  of  light  benzines  being 
about  0'4840,  that  of  heavy  benzines  0'4679,  that  of  masut  O'SOIO,  and  that 
of  oil  of  paraffin  0'5424.  The  coefficient  of  expansion  is  0 '00063  and  the  heat  of 
combustion  10,000  to  11,500  Cals.,  that  of  paraffin  wax  being  about  11,000  Cals. 

The  heat  of  evaporation  (i.  e.,  the  heat  necessary  to  transform  1  kilo  of  liquid 
at  the  boiling-point  into  vapour  at  the  same  temperature)  varies  with  the 
density  of  the  different  fractions ;  for  a  product  of  density  0'640  and  b.-pt.  40°, 
it  is  80-6  Cals.,  for  one  of  density  0'743  and  b.-pt.  93°,  68  Cals.,  and  for  one 
of  density  0'813  and  b.-pt.  176°,  51'6  Cals. 

Montechino  petroleum  has  the  sp.  gr.  0-740;  that  of  Velleia,  0'780; 
American,  O'SOO  to  0'870  ;  Russian,  0'850  to  0'900 ;  and  Galician,  0'827  to  0'890. 

Different  petroleums  are  composed,  as  a  rough  mean,  of  13  per  cent,  of 
hydrogen  and  87  per  cent,  of  carbon,  small  proportions  of  oxygen,  nitrogen, 


COMPOSITION     OF     PETROLEUM  71 

and  sulphur  compounds  being  also  present.  The  hydrocarbons  present  in 
petroleum  are  numbered  by  the  hundred,  and  they  belong  to  different  series, 
one  or  other  of  which  preponderates  according  to  the  source.  Thus,  Pennsyl- 
vanian  petroleums  are  constituted  almost  exclusively  of  hydrocarbons  of  the 
saturated  series  CnH2n+2  (derivatives  of  methane),  which  are  also  found  in 
Galician  petroleums,  etc. 

Some  petroleums  contain  as  much  as  40  per  cent,  of  hydrocarbons  solid 
at  the  ordinary  temperature  (paraffin  wax),  and  these  are  left  after  distillation 
(e.g.,  Java  petroleum);  usually,  however,  much  less  than  this  is  present, 
American  petroleums  having  only  2 '5  to  3  per  cent.,  and  those  of  Baku  some- 
times only  0'25  per  cent.  Different  petroleums  may  be  distinguished  by  means 
of  the  ultra-microscope,  the  paraffin  wax  being  dissolved  in  the  colloidal 
condition. 

It  is  maintained  by  various  chemists  that  the  paraffin  wax  is  not  pre-existent 
in  petroleum,  but  is  formed  during  its  distillation.  This  is  contradicted  by 
the  fact  that  some  petroleum  pipes  show  deposits  of  paraffin  wax,  and  this 
may  also  be  separated  from  cold  petroleum  by  special  solvents. 

Hydrocarbons  of  the  unsaturated  ethylene  series,  CnH2n,  preponderate  in 
the  petroleums  of  Burma  and  are  abundant  in  those  from  California;  Penn- 
sylvanian  petroleum  contains  about  3  per  cent.  Different  petroleums  may 
hence  be  distinguished  by  the  quantities  of  bromine  or  iodine  which  they  fix, 
by  the  amounts  of  hydro bromic  or  hydriodic  acid  then  formed  (Park  and 
Worthing,  1910)  or  by  the  quantities  of  ozone  they  take  up  (Molinari  and 
Fenaroli,  1908). 

Hydrocarbons  of  the  same  general  formula,  CreH2n,  but  saturated  (cyclic  com- 


pounds, so-called  naphthenes,  or  derivatives  of  cyclopentane,  CH2 


XCH2—  CH2 
/CH2 — CH2s 

or  cyclohexane,  GH-Z\.  /CH2)  form  80  per  cent,  of  Baku  petroleums 

CH2 — CH2 

and  occur  abundantly  in  those  of  Galicia,  together  with  about  10  per  cent, 
of  hydrocarbons  of  the  aromatic  series  [recently  (1910)  hexahydrocumene  has 
been  identified]. 

Borneo  petroleum  contains  up  to  5  per  cent,  of  toluene  and  also  benzene, 
and  these  were  utilised  by  the  French  and  British  during  the  war  to  prepare 
toluene  for  making  explosives. 

In  a  Russian  petroleum  and  also  in  a  Roumanian  one,  Molinari  and  Fenaroli 
(1908)  found  hydrocarbons  derived  from  naphthenes  with  two  double  linkings 
and  having  the  general  formula  CnH2n^14  (for  example,  C17H20). 

In  certain  petroleums  small  quantities  of  acetylene  derivatives  occur. 

The  formolite  reaction  l  permits  of  the  detection  of  unsaturated  components, 

1  The  formolite  reaction  was  suggested  in  1904  by  Nastjukov,  who  showed  that,  when  treated 
with  formaldehyde  and  sulphuric  acid,  all  unsaturated  cyclic  compounds,  that  is,  benzene 
derivatives  and  alicyclic  derivatives  containing  at  least  one  double  linking,  give  an  insoluble, 
complex  condensation  product  or  formolite,  which  contains  C,  H,  0  and  S  (see  Baekelite ).  This 
reaction  is  used  to  separate  from  mineral  oils  cyclic  compounds  with  double  linkings.  To  the 
mineral  oil,  dissolved  in  twice  its  quantity  of  petroleum  benzine,  is  added  an  equal  weight  of 
concentrated  sulphuric  acid,  the  mixture  being  then  cooled,  shaken  with  one-half  its  weight  of 
40  per  cent,  formaldehyde  solution,  and,  after  half  an  hour,  poured  into  six  times  the  weight 
of  ice  water;  the  liquid  is  then  filtered  and  the  insoluble  matter  dried  and  weighed.  Russian 
mineral  oils  give  10  to  24  per  cent,  of  formolite  and  the  American  oils  30  to  33  per  cent.,  whilst 
lubricating  oils  yield  no  formolite. 

The  reaction  with  nitric  acid  (Marcusson,  1911)  also  throws  light  on  lubricating  mineral  oils  : 
10  c.c.  of  the  mineral  oil  is  dissolved  in  petroleum  benzine  (b.-pt.  below  50°),  and  the  solution 
added  in  drops  to  30  c.c.  of  fuming  nitric  acid  cooled  to  —  10°,  50  c.c.  of  concentrated  (not 
fuming)  nitric  acid  at  —  10°  being  afterwards  added  and  the  whole  introduced  into  a  separating 
funnel.  Three  layers  are  thus  formed  :  the  lowest,  acid  layer  contains  all  the  compounds  soluble 
in  nitric  acid  and  the  uppermost,  benzine  layer  all  the  compounds  not  attacked  by  the  nitric 


72  ORGANIC    CHEMISTRY 

which  may  also  be  determined  by  means  of  the  iodine  number  (see  later  :  Fats 
and  Oils),  this  being  3'3  to  6  for  Russian  and  8  to  15  for  American  petroleum. 

It  is  found  that  petroleums  produced  in  localities  relatively  near  to  one 
another  often  have  different  compositions;  according  to  David  Pay  this  is 
due  to  the  fact  that  the  unsaturated  hydrocarbons  diffuse  less  easily  through 
sandy  or  other  soils,  and  this  system  of  natural  filtration  gives  rise  to  various 
types  of  petroleum,  with  preponderance  of  saturated  hydrocarbons  in  some 
and  of  unsaturated  hydrocarbons  in  others.  These  separations  depend  on  the 
different  surface  tensions  of  the  various  components,  as  well  as  on  the  varying 
attraction  and  surface  action  exerted  by  the  filtering  material.  This  explana- 
tion is  more  reasonable  than  that  the  separation  has  been  effected  by  distillation. 

The  products  that  distil  below  180°  are  almost  exclusively  saturated  and 
those  distilling  about  200°  mostly  unsaturated. 

The  very  small  quantities  of  oxygenated  substances  contained  in  petroleum 
(often  less  than  1  per  cent,  and  rarely  5  per  cent.)  are  composed  of  phenols 
and  organic  acids  (e.  g.,  in  Galician  petroleum). 

The  traces  of  nitrogenous  substances  found  in  various  petroleums  (see 
above)  support  the  hypothesis  of  the  organic  origin  of  petroleum. 

Almost  all  petroleums  contain  sulphur,  which  is  very  difficult  to  remove 
and  imparts  an  unpleasant  odour  and  bad  colour. 

Usually  the  proportion  of  sulphur  is  about  0-10  to  0-15  per  cent.,  but  the  petroleum 
of  Terra  di  Lavoro  contains  as  much  as  1-3  per  cent.,  while  still  more  is  found  (up  to  3  per 
cent.)  in  those  of  Texas,  Ohio,  Indiana,  and  Virginia,  from  which  it  has  to  be  separated 
(see  later). 

The  nature  of  the  sulphur  compounds  present  has  not  yet  been  completely  denned, 
but  the  presence  of  merqaptans,  thio-ethers,  and  thiophene  and  its  homologues  (methyl- 
and  dimethyl-thiophene)  has  been  detected.  According  to  Heusler  it  is  only  necessary  to 
heat  a  little  of  the  petroleum  with  a  granule  of  aluminium  chloride  to  detect  the  presence 
of  sulphur,  hydrogen  sulphide  being  then  developed. 

Also  by  fractional  distillation  and  partly  by  the  specific  gravity,  the  four  principal 
types  of  petroleum  may  be  distinguished.  The  products  distilling  below  150°  form  the 
benzines  (see  later),  then  up  to  280°  are  obtained  lighting  oil  or  solar  oil  (or  kerosene),  and 
after  300°  remain  products  used  for  the  extraction  of  paraffin  wax  and  vaseline  (American) 
or  for  the  preparation  of  mineral  lubricating  oils  (Russian) : 


Crude  petroleum. 

Specific  gravity. 

Benzine. 

Solar  oil. 

Residue. 

Pennsylvania  1    . 

.       0-79-0-82 

10-20  % 

55-75  % 

10-20  % 

Ohio            .          . 

.       0-80-0-85 

10-20  % 

30-40  % 

35-50  % 

Caucasus    . 

.       0-85-0-90 

0-2-5    % 

25-30  % 

60-65  % 

Roumania 

0-85 

3-10  % 

70-80  % 

10-15  % 

Galicia 

.       0-82-0-90 

5-30o/0 

35-40  % 

30-50  % 

Italy  (Piacenza) 

.       0-74-0-79 

25-40  % 

55-65  % 

4-8    % 

Alsace 

0-912 

'K  o/ 

°    /O 

35-70  % 

55-60  % 

acid;  the  intermediate,  oily  layer  is  small  (3  to  5  per  cent.)  and  of  a  blackish-brown  colour. 
The  bottom  layer  is  dropped  on  to  ice,  a  solid,  yellow  substance  (aromatic  and  other  nitro- 
derivatives)  separating,  which  is  collected  on  a  filter,  dried  and  weighed.  The  top  layer  is  heated 
to  expel  the  benzine,  the  paraffins,  naphthenes,  and  polynaphthenes  then  remaining.  ' 

With  formolite  there  separate  the  cyclic,  aromatic,  and  alicyclic  compounds,  while  nitric 
acid  acts  on  all  unsaturated  (cyclic  and  aliphatic)  compounds.  American  mineral  oils  give  larger 
proportions  of  nitrated  products  than  the  Russian  (these  are  more  resistant  to  the  action  of 
nitric  acid).  The  formolite  reaction  separates  the  less  viscous  products  (less  lubricating),  whilst 
nitric  acid  acts  also  on  viscous  components  of  good  lubricating  properties  (olefines  and  possibly 
polynaphthenes  to  some  extent). 

1  The  varying  nature  of  American  petroleums  is  shown  by  the  following  results  :  Pennsyl- 
vanian  and  similar  petroleums  yield  60  per  cent,  of  lighting  oil,  12  per  cent,  of  benzine,  12  per  cent, 
of  lubricating  oils,  12  per  cent,  of  fuel  oils,  and  1-5  per  cent,  of  paraffin  wax,  whilst  Californian 
petroleums  give  13  per  cent,  of  lighting  oil,  5  per  cent,  of  benzine,  51-4  per  cent,  of  lubricating 
oils,  and  30  per  cent,  of  fuel  oils  (considerable  losses  occur  during  the  refining  of  Californian 
petroleum).  These  figures  show  why  crude  Pennsylvanian  petroleum  costs  three  times  as 
much  as  that  from  California. 


EXTRACTION     OF     PETROLEUM 


73 


In  some  of  the  islands  of  the  Caspian  Sea  (Tscheleken)  is  found  a  petroleum  resembling 

the  American  type,  with  a  large  proportion  of  paraffin  wax  (5-5  per  cent. ),  and  in  Columbia 

(S.  America)  petroleums  like 

those  of  Russia  (Caucasus) 

occur. 

The     Italian    petroleums 

vary   considerably   in    com- 
position and  those  of  Emilia 

and  Piacenza  are'  so  pale  and 

so  rich  in  benzine  and  poor 

in   residues  that  it  is   sup- 
posed   that     they    are     the 

condensed    or    diffused    (see 

above )  more  volatile  products 

of  more  important  deposits 

not  yet  discovered.     In  the 

distillation    of    the    Velleia 

petroleums    at     Fiorenzuola 

d'Arda     the     little     residue 

obtained    is    added    to    the 

crude  petroleum  to  be  refined 

and  thus  becomes  distributed 

in  the  lighting  oil,  so  that  the 

less     remunerative    residues 

are    never    placed    on    the 

market.      The     absence     of 

optical      activity      in      the 

petroleums     of     Montechino 

and  Velleia  (see  above)  seems 

to  confirm  the  view  that  they 

are  derived  from   more  im- 
portant deposits,    in    which 

optically     active      products 

would  probably  be  found. 
EXTRACTION       AND 

INDUSTRIAL   TREAT- 
MENT OF  PETROLEUM. 

From  the  most  remote  times 

petroleum  has  been  raised  in 

China    by    means    of    wells 

similar  to  the  present  artesian 

ones,  which  the  Chinese  used 

many  centuries  before 

Europeans  for  obtaining  drinking  water.     In  other  regions  in  times  gone  by  the  petroleum 

flowing  at  the  surfaces  of  the  water- courses  began  to  be  separated  and  used ;   then  wide, 

shallow  wells  were  dug  and  the  petroleum  raised  to  the 
surface  in  buckets.  Nowadays,  however,  petroleum  is 
everywhere  obtained  by  wells  bored  into  the  earth  like 
artesian  wells,  and  sometimes  the  petroleum  flows  to  the 
surface  under  great  pressure,  so  that  it  forms  a  fountain 
(see  Note,  p.  74,  and  Fig.  80).  It  is  supposed  that  the 
deposits  of  petroleum  in  the  interior  of  the  earth's  crust  are 
situated  in  large  cavities  or  pockets,  where  there  is  often  a 
lower  layer  of  salt  water  (Fig.  81,  W)  and  on  this  floats  a 
more  or  less  abundant  layer  of  petroleum  E ;  in  general, 
the  upper  part  of  the  pocket  is  filled  with  inflammable  gas, 
O,  which  exerts  great  pressure.  If  the  boring,  B,  reaches 

one  or  the  other  layer,  one  or  the  other  product  is  obtained  in  preponderance  or  even 

exclusively,  and,  after  the  aqueous  layer  is  exhausted,  the  same  well  may  yield  only  petroleum. 


FIG.  80. 


FIG.  81. 


74 


ORGANIC    CHEMISTRY 


The  sinking  of  a  well  is  begun  with  a  boring  35  to  40  cm.  in  diameter  by  means  of  suitable 
boring  tools  worked  by  long  rods  and  toothed  gearing,  or  by  compressed-air  drills  mounted 
on  wooden  structures  termed  derricks  (Fig.  82);  the  detritus  of  the  bored  rock  is  con- 
tinually carried  away  from  the  boring  by  a  current  of  water,  whilst  in  former  times  the 
much  slower  dry  boring  was  preferably  employed.  When  the  petroleum  layer  is 
approached,  the  water  of  the  well  or  tube  begins  to  show  drops  of  petroleum.  The  power 

is  often  supplied  by  portable  steam- 
engines,  which  should  not  be  placed  too 
near  the  boring,  since  if  the  petroleum 
or  gas  escapes  accidentally  in  any 
quantity  during  the  boring,  it  may 
ignite  and  cause  considerable  damage 
by  fire  or  explosion. 

In  such  cases  it  is  hence  advisable 
to  transform  the  energy  on  the  site,  for 
instance,  with  electric  motors.  Even 
then  fires  and  explosions  have  been 
caused  by  the  accidental  ignition  of  the 
gas  mixed  with  air,  by  sparks  formed 
by  stones,  issuing  violently  from  the 
well  along  with  sand  and  petroleum  and 
striking  the  iron  framework  or  the  rails 
of  the  woodwork.1 

When  the  petroleum  is  not  exuded 
under  pressure,  it  is  often  raised  by 
means  of  pumps,  but  this  is  not  possible 
where  much  sand  (up  to  30  per  cent. ) 
is  also  extracted  and  has  to  be  allowed 
to  deposit;  this  is  the  case  at  Baku, 
where,  however,  one-third  of  the 
petroleum  issues  under  pressure. 

During  recent  years   there  have  re- 
mained relatively  few  "  fountains  "  at 
Baku,  and  the  petroleum  of  the  sandy  wells,  which  cannot  be  raised  by  pumps,  is  extracted 

1  Artesian  wells  for  extracting  petroleum  have  an  average  diameter  of  36  to  50  cm.,  and  vary 
in  depth  according  to  the  region;  at  Baku  they  were  first  of  all  60  to  150  metres  deep,  but  of 
recent  years  wells  have  usually  been  sunk  to  a  depth  of  250  to  350  metres  (occasionally  1000 
metres).  In  the  Washington  district  of  the  United  States  the  wells  are  from  700  to  850  metres 
deep,  and  near  Pittsburg  is  the  deepest  of  all,  1820  metres.  The  wells  are  100  to  200  metres 
apart  according  to  the  locality,  and  they  remain  active  for  five  to  ten  years. 

The  cost  of  boring  varies  with  the  district,  that  is,  with  the  nature  of  the  subsoil,  and,  under 
favourable  conditions  and  for  wells  not  too  deep,  each  boring  costs  about  £400.  Those. made  in 
the  Washington  district  cost  even  £1400  to  £1600.  At  Velleia,  in  the  province  of  Piacenza,  the 
wells  are  little  more  than  100  metres  deep,  whilst  at  Salsomaggiore  they  have  been  bored  to  a 
depth  of  400  metres,  and  in  one  case  of  700  metres,  in  order  to  utilise  for  medical  purposes  the 
iodine-salt  water  which  is  obtained,  together  with  a  little  petroleum.  In  America  the  well  is 
widened  at  its  lowest  point,  where  it  meets  the  petroleum,  by  exploding  a  dynamite  cartridge 
("  torpedoing  " ). 

A  well  sunk  in  1891  at  Balakhany,  270  metres  deep,  gave  an  uninterrupted  jet  producing 
3276  tons  of  petroleum  per  twenty -four  hours,  and  the  mass  of  sand  expelled  covered  the  whole 
neighbourhood.  A  little  distance  away  one  of  the  Nobel  Company's  wells,  in  1892,  gave  13,000 
tons  per  day.  In  February  1893  a  well  was  sunk  at  Romany,  near  Baku,  which  for  several 
weeks  yielded  10,000  tons  of  petroleum  per  day ;  the  oil  issued  from  the  earth  with  such  violence 
that  the  movement  of  the  air  broke  the  windows  of  neighbouring  houses,  and,  as  at  first  it  was 
not  possible  to  guide  the  jet  into  horizontal  channels,  all  the  iron  plates  used  for  this  purpose 
being  pierced,  250,000  tons  of  petroleum  were  lost  in  five  weeks.  In  1909  a  new  well  at  Baku 
gave,  for  a  long  time,  3500  tons  of  naphtha  per  day.  A  well  bored  at  Maikop  (70  kilos  from  the 
Black  Sea),  on  September  12,  1910,  to  a  depth  of  70  metres,  gave  a  jet  04  metres  above  the  surface 
of  the  ground  and  a  production  of  6000  tons  in  twenty -four  hours ;  on  September  18  the  fountain 
caught  fire  and  five  days  passed  before  it  could  be  extinguished. 

Fountains  as  rich  as  this  are  exceptional;  usually  wells  yield  much  less,  and  at  Baku  a  well 
is  generally  abandoned  when  it  gives  less  than  four  tons  in  twenty -four  hours.  In  Italy,  however, 
wells  are  used  which  give  only  a  few  hundredweights  of  petroleum  per  day ;  some  of  the  Italian 
wells  produce  only  60  litres  a  day,  others  as  much  as  2500  litres  or  more. 


FIG.  82. 


DISTILLATION     OF    PETROLEUM 


75 


by  special  "  bailers  "  made  of  a  cylinder  of  sheet- metal  terminating  in  a  cone  and  fitted  in 
the  lower  portion  with  a  valve  which  opens  when  the  bailer  (called  the  shalonka)  becomes 
immersed  in  the  petroleum  and  closes  on  raising  by  means  of  pulleys  and  windlass,  the 
steel  rope  carrying  the  bailer  being  wound  round  a  large  drum  a  short  distance  from  the 
well.  The  shalonka,  containing  some  hectolitres  of  petroleum,  is  discharged  by  inverting 
it  over  a  channel. 

From  the  large  masonry  or  clay  reservoirs  near  the  wells,  the  petroleum  passes  by 
means  of  iron  pipes  to  the  iron  tanks  (holding  5000  or  even  10,000  cu.  metres)  of  the 
refineries  or  to  the  despatching  stations  (suitable  trains  or  vessels),  which  at  Baku  are  very 
near,  but  in  America  some  hundreds  of  miles  from  the  wells;  these  pipes  then  traverse 
plains,  mountains,  and  valleys,  and  in  the  same  way  and  with  the  help  of  powerful 
pumping-stations,  the  refined  petroleum  is  despatched  to  the  place  of  loading.  In  1905, 
the  Standard  Oil  Company  began  the  construction  of  another  such  pipe  (pipe-line)  to 
connect  the  works  at  Kansas  City  with  the  coast;  the  distance  is  about  1700  miles  and 
the  construction  cost  £880,000  and  served  to  transport  daily  from  10,000  to  15,000  barrels 
of  petroleum.1 

To  protect  stores  of  petroleum  from  lightning  and  fire  the  same  precautions  as  for 
explosives  are  employed  (see  later),  while  the  tanks  are  so  constructed  that,  in  case  of  fire, 
streams  of  burning  petroleum  cannot  reach  other  places. 

DISTILLATION.  Crude  petroleum  cannot  be  used  for  lighting,  as  it  has  a  bad 
smell  and  colour,  contains  many  impurities,  and  is  composed  partly  of  excessively 
volatile  products,  which  might  easily  cause  explosions  or  fires  in  the  lamps.  In  order  to 
avoid  these  dangers,  the  petroleum  is  subjected  to  exact  refining,  which  is  controlled  by 
legal  enactments  and  with  special  apparatus  (see  later). 

The  refining  is  carried  out  in  a  manner  which  varies  with  the  nature  of  the  petroleum 
and  usually  consists  of  a  fractional  distillation  and  a  chemical  purification.2 

1  The   problem   of    transporting  petroleum   to  great   distances   through   pipes  is   far  more 
complex  than  it  seems  at  first  sight.     The  capacity  of  a  pipe  is  proportional  to  the  square 
root  of  the  fifth  power  of  the  diameter  and  depends  on  the  pressure  of  the  pump,  the  length 
of    the    pipe,    the   differences    of    level   to   be   overcome   and   the   viscosity   of   the    liquid. 
Transport  difficulties   encountered   especially  with   petroleums  very  rich  in   bituminous  sub- 
stances   and    very    dense,   were  overcome  when  it    became    possible   in  America    to   make 
homogeneous  iron  pipes  eight  inches  in  diameter  and  capable  of  resisting  pressures  of  60  to  105 
atmospheres.     Recently,  however,  it  has  been  shown  by 

Isaac  and  Buckner  Speads  that  admixture  of  10  per 
cent,  of  water  with  the  pftroleum  diminishes  the 
friction  in  the  pipes  to  an  enormous  extent,  especially 
if  the  inner  surface  of  the  pipe  is  given  a  spiral 
form ;  the  liquid  then  assumes  a  rotatory  movement 
with  the  water  at  the  periphery,  so  that  the  friction 
of  the  petroleum  is  exerted  on  the  water  and  not  on 
the  surface  of  the  pipe.  To  prevent  stoppage  of  the 
pumps  from  causing  the  establishment  of  an  uninter- 
rupted column  of  petroleum,  which  would  produce 
considerable  friction  on  resumption  of  working,  the 
pipe  is  made  undulating ;  the  water  then  collects  in 
the  depressions. 

If  p  denotes  the  loss  of  power  in  a  pipe  100  feet 
long,  d  the  diameter  of  the  pipe,  y  the  velocity  in 
feet  per  second,  and  k  a  constant,  then  p  =  d  k  yz. 
Experiment  shows  that  for  a  smooth  8-inch  pipe  with 
pure  petroleum,  k  =  70,  and  with  petroleum  and  10  per 
cent,  of  water  k  =  41,  whilst  with  a  pipe  having  a 
spiral  inner  surface  (with  10  per  cent,  of  water), 
&  =  0-37  —  0-49.  Through  one  and  the  same  pipe 
petroleums  and  oils  of  different  qualities  may  be  passed 
successively  without  danger  of  mixture,  owing  to  the 
high  pressure  in  the  pipe.  This  is  explained  by  the 
fact  that,  while  the  10  per  cent,  of  water  is  transported 
with  some  degree  of  friction,  the  90  per  cent,  of 
petroleum,  which  does  not  mix  with  the  water,  slips 
and  glides  over  the  latter  with  extraordinarily  little 
friction. 

2  The   fractional   distillation  in    the   laboratory   is 
carried    out    in    Engler    flasks    (Fig.    83),    which    are 
of  definite  size  and  shape  and  permit  of  concordant 


FIG.  83. 


76 


ORGANIC    CHEMISTRY 


The  industrial  refining  of  petroleum  consists  in  separating  the  crude  petroleum  into 
these  three  groups,  I,  II,  and  III. 

Apparatus  is  used  for  discontinuous,  or  for  continuous,  distillation. 

Discontinuous  distillation  is  conveniently  carried  out  in  the  so-called  waggon-still  largely 
used  in  America  and  at  Baku.  It  holds  as  much  as  2500  barrels  at  a  time  (Figs.  84  and  85). 

It  is  made  of  wrought-iron  10  to  14  mm.  in  thickness,  and  has  a  corrugated  bottom; 
it  is  commonly  7  metres  long,  4  metres  wide,  and  3  metres  deep.  The  top  is  fitted  with 
tliree  flanged  elbows  which  carry  off  the  vapour.  In  thirty  hours  three  distillations  can 
be  carried  through,  the  residues  being  discharged  through  the  three  orifices,  c.  The 
heating  is  effected  by  means  of  these  residues,  which  are  forced  into  perforated  pipes,  r, 
in  the  double-arched  hearth;  rational  circulation  of  the  products  of  combustion  results  in 
effective  utilisation  of  the  heat. 

More  profitable  use  is  now  made  of  simpler,  cylindrical  boilers,  which,  although  of 
larger  dimensions,  correspond  almost  exactly  with  the  various  types  of  steam-boilers, 
the  heating  being  external,  or  lateral,  or  internal,  or  two  of  these  together.  Such  boilers 
of  600  to  700  or  more  barrels  capacity  are  commonly  used  even  in  America,  where,  however, 
both  the  more  complex  and  more  perfect  Lugo  apparatus  and  the  Rossmjissler  apparatus, 
in  which  the  heating  is  effected  by  superheated  steam,  are  also  employed. 


FIG.  85. 


For  the  condensation  of  the  vapours  that  distil  over,  complicated  iron  coils  are  arranged 
in  cisterns  through  which  cold  water  circulates  continuously,  the  bore  of  the  pipe  being 
20  to  25  cm.  at  first  and  gradually  diminishing  to  5  to  8  cm. 

The  distillate  with  specific  gravity  not  exceeding  0-750  and  b.-pt.  150°  forms  the  crude 
benzine  and  is  collected  and  worked  up  separately.  The  distillate  with  sp.  gr.  0-750  to  0-860 
forms  the  lighting  oil,  and  the  residue  is  treated  separately. 

At  the  end  of  the  distillation,  decomposition  of  the  substances  of  higher  molecular 
weight  is  avoided  by  direct  injection  into  the  mass  of  superheated  steam  (in  many  American 


results    being    obtained    in    all    laboratories;    the 

following    fractions 

are    then    weighed 

separately  : 

Boiling-point. 

Specific  gravity. 

I.  Light  or  readily  volatile  petroleums  : 

(a)  Petroleum  ether        ..... 

40-70° 

0-635-0-660 

(b)  Gasolene          ...... 

70-80° 

Or660-0-667 

(c)  Benzine           ...... 

80-100° 

0-667-0-707 

(d)  Ligroin  (burnt  in  special  lamps  for  lighting) 
(e)  Petroline  (used  for  de-fatting  or  cleaning)  . 

100-120° 
120-150° 

0-707-0-722 
0-722-0-737 

II.  Petroleum  for  lighting  : 

I  quality       ....... 

150-200°  1 

II  quality     ........ 

200-250°  [ 

0-753-0-864 

Ill  quality  ....... 

250-300°J 

' 

III.  Residues  of  the  distillation  : 
(a)  Heavy  oils  :  lubricating  oils 
(b     Paraffin  oil 
(c)  Coke      .... 


above  300° 


0-7446-0-8588 
0-8588-0-9590 


CONTINUOUS    DISTILLATION 


77 


factories,  however,  decomposition  of  these  products  is  purposely  effected,  see  later),  so  that 
heavier  lamp  oils  distil  and  condense  with  the  water,  while  the  residue  (masut)  is  better 
suited  to  the  preparation  of  heavy  cylinder  oils.  This  masut  is  then  distilled  in  other 
stronger  vessels  under  reduced  pressure  (see  later  :  Lubricating  Oils)  and  with  superheated 
steam  at  400°,  yielding  a  distillate  of  medium  oils  easily  separable  from  the  water  and  a 
vacuum-concentrated  residue  serving  for  the  preparation  of  an  excellent  dark  cylinder  oil, 
which  has  a  flash-point  above  280°  and  contains  paraffin  wax  in  the  colloidal  state. 

Continuous  distillation  is  employed  more  especially  at  Baku,  with  large  plants  con- 
sisting of  boilers  arranged  in  series  so  that  each  boiler  is  maintained  at  a  definite,  constant 
temperature,  the  vapours  passing  from  one  boiler  to  the  other  only  depositing  in  a  con- 
densed form  those  portions  corresponding  with  a  given  boiling-point  and  a  given  specific 
gravity.  By  feeding  the  first  boiler — which  is  at  the  highest  temperature-^continuously, 
the  others  are  also  fed  indirectly  and  kept  full,  each  of  them  discharging  a  fraction  of  a 
definite,  constant  specific  gravity.  Naturally  the  higher  temperature  boilers  are  furnished 
with  dephlegmators  (Fig.  86),  which  cause  ready  deposition  of  the  heavy  oil  carried  over 
with  the  very  hot  vapours.  In  these  boilers  the  heating  or  distillation  is  effected  by  means 
of  superheated  steam,  which  is  usually  obtained  by  passing  steam  from  a  boiler  (D,  Fig.  87 ) 
through  a  series  of  iron  pipes  heated  in  a  furnace  by  direct-fire  heat. 

In  addition  to  other  advantages,  continuous  distillation  gives  an  increase  of  30  per 
cent,  in  the  amount  of  lamp  oil.  The  residue  left  after  distilling  the  crude  petroleum  up 
to  280°  bears  the  Tartar  name  of  masut  or  the  Russian  one  of  astatki  (ostatki).  The  amount 


FIG.  86. 


FIG.  87. 


of  petroleum  distilled  in  twenty-four  hours  corresponds  with  four  times  the  capacitv  of  all 
the. boilers  in  the  battery. 

The  Nobel  Company  at  Baku  has  boilers  which  distil  1000  tons  of  petroleum  in  twenty- 
four  hours.  During  recent  years  rectifying  columns  similar  to  those  used  for  alcohol 
have  been  employed,  these  admitting  of  a  large  production  without  the  use  of  large 
boilers. 

In  the  "  Black  Town,"  near  Baku,  there  are  200  refineries,  which  treat  the  whole  of  the 
petroleum  of  the  district.  The  odour  of  petroleum  is  perceptible  at  a  great  distance,  and 
the  town  is  always  covered  and  surrounded  with  dense,  black  smoke.  The  most  important 
refinery  is  that  of  Nobel  Brothers,  which  refines  one-half  of  the  annual  output  of  the  Caspian, 
although  this  firm  possesses  only  one-eighth  of  the  total  number  of  wells. 

The  Kubierschky  column  (see  later  :  Benzine)  does  not  appear  to  be  suited  to  the  distilla- 
tion of  petroleum.  In  distilling  crude  petroleum  at  Baku,  as  much  as  5  per  cent,  of  fuel 
(heavy  oils  or  residues)  was  at  one  time  used,  but  the  mean  consumption  was  3-85  per  cent, 
in  1909  and  3-42  per  cent,  in  1911,  and  under  the  most  favourable  conditions  was  only 
2-5  per  cent. ;  still  greater  economy  might,  however,  be  effected.  To  distil  Surachany 
petroleum  19,627  Cals.  are  required  per  100  kilos,  but  during  the  condensation  17,359  Cals. 
are  recoverable. 

The  Bayonne  works  of  the  Standard  Oil  Company  at  New  Jersey  deals  with  raw 
petroleum  comparatively  poor  in  benzine  and  lamp  oil  and  rich  in  heavy  oil.  Since  the 
lighter  products  are  preferred,  the  crude  oil  is  subjected  to  an  initial  distillation,  which  is 
prolonged  as  far  as  the  final  products.  Two  qualities  of  lamp  oil  (sp.  gr.  0-730  to  0-807  and 
0-800  to  0-808)  are  collected  separately,  and  direct  superheated  steam  is  used  to  raise  the 
temperature  to  350°  or  even  390° ;  a  mixture  of  equal  parts  of  water  and  a  dense  medium 
oil  (sp.  gr.  above  0-850,  viscosity  3  at  20°)  is  thus  obtained  which  is  of  poor  quality  as 


78 


ORGANIC    CHEMISTRY 


lighting  or  lubricating  oil,  but  serves  for  making  oil-gas  (see  p.  64)  by  dropping  it  into  red- 
hot  retorts,  and  also  for  carburetting  water-gas  and  for  gas-engines.  The  temperature  is 
then  raised  still  higher  without  evacuating  and  without  the  use  of  steam,  this  being  a 
modified  form  of  "  cracking  "  (see  later) ;  the  vapour  distilling  from  the  large,  horizontal, 
iron  vessels  used  passes  into  a  dephlegmating  column  filled  with  stone  situate  above,  the 
products  of  higher  boiling-point  being  condensed  and  returned  to  the  vessel  to  undergo 
further  decomposition,  whilst  the  vapours  of  the  lighter  products  pass  to  the  condensers. 
The  heating  is  carried  out  by  means  of  small  anthracite,  which  is  more  economical  than 
using  petroleum  residues,  as  is  practised  in  Russia  and  Austria.  The  heavier  products 
which  distil  last  are  naturally  kept  separate  from  the  raw  petroleum  distilling  first  and 
from  the  benzine,  and  the  distillation  is  continued  until  oil  rich  in  paraffin  wax  no  longer 
distils  over  and  there  remains  in  the  still  petroleum  coke,  which  is  used  for  making  arc-lamp 
carbons.  These  last  oils  are  intensely  cooled  with  brine  from  a  refrigerating  machine 
(see  Vol.  I.,  pp.  260,  621),  this  circulating  round  large,  horizontal  iron  cylinders,  through 
which  the  oil  is  transported  from  end  to  end  by  means  of  a  revolving  vaned  shaft ;  the 

oil,  which  is  thus  cooled  to  4°  to  5°  and 
then  exhibits  the  consistency  of  butter, 
is  next  passed  into  large  filter-presses, 
these  retaining  the  paraffin  wax  in  cakes 
(see  later).  The  dense  oils  passing  through 
the  filters  serve  for  the  manufacture  of 
lubricating  oils. 

CHEMICAL  PURIFICATION  OF 
PETROLEUM.  The  petroleum  distilling 
between  150°  and  300°  is  not  yet  suitable 
for  lighting  purposes,  as  it  has  a  marked, 
rather  unpleasant  odour  and  a  faint  yellow 
colour,  and  contains  substances  which 
detract  from  its  value.  It  was  Eichler 
at  Baku'  who  first  suggested  (1865) 
purification  by  means  of  concentrated 
sulphuric  acid. 

This  is  carried  out  in  large  iron  tanks 
with  conical  bases  (Fig.  88 ),  the  petroleum 
being  treated  with  several  separate 
quantities  (altogether  1  to  3  per  cent.) 
of  concentrated  sulphuric  acid  of  66°  Be. 
(nowadays  the  monohydrate  obtained  by 
the  catalytic  process),  the  mixture  being 
vigorously  agitated  by  compressed  air 
blown  in  at  the  bottom  of  the  tank,  and 
each  quantity  of  the  acid  separated  after 

half  an  hour's  rest.  The  first  addition  of  about  0-5  per  cent,  of  acid  serves  also  to  dry  the 
petroleum,  the  remainder  being  added  in  two  portions. 

The  sulphuric  acid  acts  especially  on  the  aromatic  hydrocarbons  (forming  sulphonic 
acids),  the  defines  and  the  oxygenated  acid  compounds,  as  well  as  on  the  colouring  and 
sulphur  substances.  The  sulphuric  anhydride  attacks  also  the  naphthenes  to  some  extent. 
Sulphuric  acid  has  a  polymerising  action,  so  that  a  small  part  (1  to  3  per  cent.)  of  the  petro- 
leum is  resinified  and  the  acid  is  turned  black  by  the  dissolved  resins,  but  may  still  be  used 
for  the  manufacture  of  superphosphates.1  In  order  to  weaken  the  action  of  the  acid  some- 

1  According  to  Ger.  Pat.  221,615  of  1909  this  black  acid,  containing  sometimes  as  much  as 
2-5  per  cent,  of  complex  organic  substances,  may  be  purified  by  causing  it  to  fall  into  pure,  boiling 
sulphuric  acid  through  which  a  current  of  air  is  passed ;  all  the  acid  distilling  over  is  then  pure 
and  colourless.  In  California  the  refineries  use  oleum,  and  the  black  acid  recovered  is  mixed 
with  coke  or  other  suitable,  readily  oxidisable  organic  substances  and  heated,  most  of  the  sulphuric 
acid  being  converted  into  sulphur  dioxide,  which  is  then  used  for  making  catalytic  oleum.  In 
some  refineries  the  black  acid  is  poured  carefully  into  about  an  equal  weight  of  water  (giving 
an  acid  of  30°  Be. ),  the  tarry  mass  then  separating  at  the  surface  being  decanted  off  and  utilised, 
and  the  residual  acid  either  mixed  with  that  used  for  the  manufacture  of  superphosphates  or 
heated  at  140°  to  150°  in  leaden  vessels  so  as  to  concentrate  it  to  60°  Be.,  the  tarry  matters 
remaining  dissolved  being  thus  separated  or  carbonised.  After  being  washed  with  water,  tli3 


FIG.  88. 


PURIFICATION     OF     PETROLEUM  79 

what,  it  is  mixed  with  sodium  sulphate ;  further,  in  order  that  yellowing  of  the  petroleum 
may  be  avoided,  sulphuric  acid  containing  less  than  0-01  per  cent,  of  nitrous  acid  should 
be  employed.  After  the  action  of  the  acid,  the  petroleum  is  washed  in  lead-lined  vessels 
thoroughly  with  water  and  then  with  1  to  1-5  per  cent,  of  concentrated  caustic  soda  solution 
(20°  to  25°  Be. ),  air  being  passed  in  from  beneath  to  effect  mixing ;  in  this  way  the  traces 
of  acid  remaining  and  also  the  phenolic  compounds  are  removed.  After  the  alkali  has  been 
separated,  the  oil  is  again  well  washed  with  water.  The  remaining  petroleum  is  not  clear, 
as  it  is  emulsified  with  a  little  water,  but  it  clarifies  on  standing  or  more  rapidly  on  being 
filtered  through  sawdust  and  salt  or  Fuller's  earth  (see  Vol.  I.,  p.  738)  by  means  of  filter- 
presses,  all  traces  of  emulsion  being  thus  removed.1 

In  recent  years  Edeleanu  has  applied  in  Roumania  a  new  method  of  purifying  very 
viscous  petroleum  residues  by  means  of  liquid  sulphur  dioxide,  which  very  readily  dissolves 
the  unsaturated,  carbon-rich  hydrocarbons.  The  petroleum  to  be  refined  is  dried  by  passing 
it  through  dry  sodium  chloride  mixed  with  one-fourth  of  its  weight  of  calcium  chloride  and 
is  then  cooled  in  an  iron  vessel  to  —  10°.  Liquid  SO2  (one-fourth  more  in  amount  than  the 
petroleum)  at  —  10°  is  then  allowed  to  fall  in  a  fine  spray  on  the  surface  of  the  liquid, 
which  is  not  mixed ;  in  a  short  time  two  layers  separate,  the  upper  one  consisting  of  petro- 
leum saturated  with  SO2,  and  the  lower  one  of  liquid  SO2  containing  in  solution  the  heavy 
unsaturated  hydrocarbons  and  other  impurities.  This  lower  layer  is  removed  as  it  forms 
to  a  tank  where,  at  a  rather  higher  temperature,  it  gives  off  the  SO2,  this  being  again 
liquefied.  The  SO2  dissolved  by  the  petroleum  is  liberated  similarly,  the  last  traces  of 
the  gas  (0-3  per  cent.)  being  removed  by  washing  with  water.  The  residue  of  heavy, 
unsaturated  hydrocarbons,  mixed  with  tar  and  other  impurities,  is  used  as  a  substitute 
for  oil  of  turpentine  or  heavy  oils.  This  process  requires  somewhat  complex  plant. 

In  1912  there  were  two  large  plants  in  Europe  making  use  of  this  process,  the  loss  of 
SO2  being  0-05  per  cent,  on  the  weight  of  petroleum  refined  and  the  inclusive  cost  6*.  lOd. 
per  ton.  The  plant  necessary  for  the  treatment  of  65  tons  of  petroleum  per  ten  hours 
costs  about  £10,000. 

Attempts  have  been  made,  without  any  marked  practical  success,  to  purify  petroleum 
by  means  of  alcohol,  hypochlorites,  bisulphites,  zinc  chloride,  etc. 

Some  crude  petroleums  give  a  rather  yellow  lamp  oil,  which  is  decolorised  by  exposure 
for  some  time  to  the  sun  in  shallow  tanks  covered  with  sheets  of  glass.  Sometimes  the 
yellow  tint  is  removed  by  dissolving  in  the  petroleum  traces  of  complementary  blue  or 
violet  dyes;  as,  however,  nearly  all  commercial  dyes  are  insoluble  in  petroleum,  it  is 
necessary  to  obtain  from  the  manufacturers  the  bases  of  the  colouring-matters,  these 
being  soluble. 

In  certain  cases,  decolorisation  is  attained  with  infusorial  earths,  clays,  or  natural 

tarry  mass  serves  either  as  a  substitute  for  tar,  or  for  impregnating  timber,  or  as  a  fuel.  Nitro- 
genous residues  (waste  horn,  hides,  leather)  are  sometimes  converted  into  nitrogenous  fertilisers 
(containing  ammonium  sulphate)  by  treatment  with  the  hot,  black  acid. 

According  to-F.  Braunlich  (Ger.  Pat.  267,873,  1913)  it  is  better  to  add  the  black  acid,  not  to 
pure  acid,  but  to  sodium  bisulphate  (or  the  potassium  or  ammonium  salt,  or  a  mixture  of  these) 
heated  to  fusion,  pure  sulphuric  acid  then  distilling  off.  J.  Fleischer  (1907)  obtains  colourless 
acid  (45°  to  50°  Be. )  by  causing  the  black  acid  to  diffuse  through  porous  partitions  washed  by  a 
little  water. 

The  concentration  of  the  acid  cannot  be  determined  by  ordinary  titration,  since  the  sulphonic 
acids  present  also  have  acid  reactions ;  these,  however,  yield  soluble  barium  salts. 

1  The  black  alkaline  liquors  from  the  refining  of  petroleum  may  be  utilised  by  concentrating 
them  in  iron  pans  to  a  syrupy  consistency  and  calcining  the  residue  in  a  muffle  furnace;  this 
procedure  yields  sodium  carbonate,  which  is  extracted  with  water  and  may  be  converted  into 
alkali  hydroxide  by  treatment  with  lime  (see  Vol.  I.,  p.  554).  Unsaturated  hydrocarbons  and 
ketones  (acetone,  etc. )  may  be  condensed  from  the  gases  evolved  from  the  muffle  furnace. 

The  black  alkali  liquors  may  also  be  used  for  the  preparation  of  the  sodium  salts  of  the 
naphthenic  acids  (e.  g.,  tridecanaphthenic  acid ;  see  later,  Naphthenes),  which  are  used  as  substitutes 
for  antiseptic  soaps  and  are  obtained  by  heating  the  liquor  in  iron  pans  in  which  bags  containing 
sodium  chloride  are  immersed.  The  heating  and  concentrating  are  continued  until  sufficient 
salt  is  dissolved  to  cause  separation  of  the  sodium  salt  of  the  naphthenic  aoids.  The  alkaline 
salt  solution  is  then  decanted  off  and  treated  as  described  above,  whilst  the  soap  substitute  is 
heated  further  until  it  gelatinises  completely,  and  is  then  despatched  in  wooden  casks;  the 
product  has  a  less  disagreeable  odour  if  a  current'  of  hot  air  or  superheated  steam  is  passed 
through  the  mass  before  the  alkaline  salt  solution  is  separated. 

The  direct  utilisation  of  the  black  alkaline  liquor  for  the  impregnation  and  preservation  of 
railway  sleepers  has  been  suggested. 


80 


ORGANIC    CHEMISTRY 


magnesium  hydrosilicates  (Fuller's  earth,  see  Vol.  I.,  p.  738),  but  these  are  not  applicable 
to  the  dense,  dark  Californian  petroleums. 

A  most  important  operation  for  petroleum  rich  in  sulphur  (present  especially  as  H2S) 
and  hence  dark  and  of  unpleasant  odour  (like  those  from  Canada,  which  can  be  used  only 
as  fuel  and  not  for  lighting  purposes)  is  that  of  a  desulphurising  according  to  the  process 
proposed  by  Frasch  (1888-1893);  this  consists  in  distilling  the  petroleum  with  an  excess 
of  a  mixture  of  metallic  oxides — powdered  copper  oxide,  75  per  cent. ;  lead  oxide,  10  per 
cent. ;  iron  oxide,  15  per  cent.  This  operation  reduces  the  sulphur- content  from  0-75  per 
cent,  or  more  to  0-02  per  cent.  It  is .  calculated  that,  by  this  method,  about  50  tons  of 
sulphur  are  extracted  daily  from  Ohio  petroleum,  most  of  it  being  lost. 

The  operation  is  carried  out  by  simple  mixing  or  by  means  of  vapour.  In  the  first 
case  6800  kilos  (6-8  tons)  of  the  oxide  mixture  are  added  to  200  tons  of  petroleum  in  a  large 
tank,  the  mixture  being  subjected  to  prolonged  agitation  by  mechanical  stirrers,  which 
keep  the  oxidising  mass  at  the  bottom  of  the  tank  in  continual  motion. 

The  petroleum  is  then  decanted  off  into  the  fractional  distilling  apparatus,  a  second 
quantity  of  200  tons  of  petroleum,  together  with  4500  kilos  (4-5  tons)  of  oxides  being  added 
to  the  residue  in  the  tank;  the  operation  is  repeated  four  or  five  times  before  renewing 
the  oxides.  The  used  oxides  are  regenerated  by  calcination,  which  removes  the  sulphur. 

The  Frasch  process  of  desulphurising  the  vapour  is  far  more  rational  and  rapid;  it 
consists  in  passing  the  petroleum  vapours  from  the  distillation  vessel  (from  100  tons  of 

petroleum)  (A,  Fig.  89)  successively  into 
two  communicating  cylinders,  B  and  C, 
placed  one  over  the  other  and  enclosed 
by  a  metal  casing,  D,  above  the  boiler. 
The  vapours  pass  first  into  the  casing, 
next  into  the  lower  cylinder,  and  then 
into  the  upper  one,  coming  into  intimate 
contact  with  the  mixture  of  metallic 
oxides,  which  is  kept  moving  and  sub- 
divided in  both  cylinders  by  means  of 
rotating  reels,  h,  provided  with  peripheral 
brushes,  H.  The  oxidising  mixtures  in 
the  two  cylinders  are  renewed  alternately, 
while  the  purified  vapours,  after  traversing 
a  gravel  filter,  0,  which  retains  particles 
FIG.  89.  of  the  oxides  carried  over,  are  condensed 

in   ordinary  coils,  F.     By    this    process, 
some  refineries  are  able  to  purify  as  much  as  11,000  tons  of  petroleum  per  day. 

Recently  petroleum  has  been  desulphurised  by  means  of  metallic  sodium,  and  treatment 
with  aluminium  chloride  in  the  hot  and  under  pressure  is  also  recommended.  V.  Walker 
(U.S.  Pat.  955,372,  1910)  passes  the  vapours  into  columns  fitted  with  perforated  plates  and 
containing  anhydrous  cupric  chloride,  the  last  traces  of  hydrogen  sulphide  being  removed 
by  passing  the  vapours  into  a  solution  of  lead  oxide  in  caustic  soda.  Robinson  (1909) 
separates  the  sulphur  by  treating  the  petroleum  with  highly  concentrated  sulphuric 
acid. 

In  well-refined  petroleums,  the  proportion  of  sulphur  is  always  less  than  0-06  per  cent., 
usually  0-02  per  cent. 

Attempts  are  sometimes  made  to  deodorise  petroleum  by  addition  of  fatty  acids  and 
tannin  and  subsequent  saponification,  or  by  addition  of  calcium  hypochlorite,  or  aluminium 
chloride,  or  bisulphites,  or  acetone,  or  formaldehyde.  The  odour  may  also  be  masked  by 
addition  of  a  perfume  (bergamot  oil,  neroli  oil,  orange-flower  oil). 

The  fliiorescence  may  be  eliminated  by  addition  of  yellow  colouring  matters  (e.  g., 
nitronaphthalene,  quinoline  yellow,  etc. ). 

PETROLEUM  TANKS.  The  refined  petroleum  is  preserved  in  large  cylindrical 
sheet-metal  tanks  (Fig.  90),  situated  near  the  works;  they  are  whitened  outside  to  reflect 
the  heat  of  the  sun,  and  are  furnished  with  charging  and  discharging  pipes  communicating 
with  the  pumping-station  by  which  all  the  liquids  in  the  works  are  circulated. 

TRANSPORT  OF  PETROLEUM.  For  transport  by  land  and  sea,  wooden  casks  hold- 
ing 159  litres  (about  145  kilos)  were  at  one  time  exclusively  used,  but  to-day  land  transport 


81 


is  effected  by  tank-cars  (Fig.  91),  which  are  now  numbered  in  thousands  (more  than  20,000 
in  the  United  States,  and  more  than  15,000  in  Russia).  For  sea  transport,  tank-steamers 
are  used  (there  are  now  360  of  these  of  the  total  capacity  of  630,000  tons)  (Fig.  92);  when 
they  arrive  at  their  destinations  in  the  ports  of  different  countries,  they  are  discharged 
by  means  of  pumps  into  storage-tanks  or  directly  into  tank-cars.  From  these  stores 
(there  are  tanks  of  2000  tons  capacity  at  Leghorn,  Savona,  Genoa,  and  Venice)  the  petroleum 
is  despatched  inland  in  wooden  or  iron  casks  or  in  cans  holding  14  kilos  (17  litres)  and 
packed  in  pairs  in  wooden  cases ;  the  wooden  casks  are  coated  inside  with  a  thin  layer  of 
glue. 

For  long-distance  transport  through  pipes,  see  note  on  p.  75. 


— J=^«r-~"    -  ''^  MSHPsSH^Il^ 

FIG.  90. 


-a^-.T-i !l;*-_±£=c^* 


FIG.  91. 


USES  AND  STATISTICS.  The  greater  part  of  refined  petroleum  is  still  used  for 
lighting  purposes,  either  in  the  old  lamps  with  flat  wicks  or  in  those  with  cylindrical  wicks 
and  flame- spreaders  or  in  lamps  with  incandescent  Auer  mantles;  it  can  be  used  advan- 
tageously for  household  illumination  in  town  and  country.  Part  of  it  is  employed  for 
power  purposes,  as  in  internal-combustion  engines  it  gives  an  efficiency  of  25  to  37  per  cent., 
whilst  coal  yields  only  12  per  cent.  However,  while  in  Russia  large  quantities  of  petroleum 
were  used  in  the  past  in  factories  and  for  locomotives,  nowadays  it  is  being  replaced  by  coal ; 
in  America,  on  the  other  hand,  the  opposite  is  the  case,  and  the  Mexican  Railway  alone 
consumed  more  than  4000  barrels  of  petroleum  per  day  for  its  locomotives  in  1908.  Its 
use  on  fast  ships  has  the  advantage  of  28  per  cent,  saving  in  space.  In  America,  about 


petrolia          petrolic        pefrolio       pftrolio      petrolic 


FIG.  92. 
Carbone,  coal ;  petrolio,  petroleum ;  macchine  e  caldaie,  engines  and  boilers. 

19,000,000  barrels  of  petroleum  were  used  altogether  for  railway  locomotives  in  1907. 
Lastly,  it  is  used  as  a  disinfectant  and  for  lubricating  engines,  etc. 

The  production  of  petroleum  has  increased  in  a  surprising  manner,  in  spite  of  the  growing 
development  of  the  gas  and  electrical  industries.  The  following  figures  illustrate  this  for 
the  two  great  petroleum-producing  regions : 


In  1874 
1884 
1894 
1905 
1910 
1916 


Caucasus  (Russia) 
Tons 

100,000 
.  1,500,000 
.  5,000,000 
.  7,969,239 
.  9,500,000 
.  9,934,000 


United  States 
Tons 

1,500,000 

3,400,000 

7,000,000 

17,636,000 

26,000,000 

40,100,000 


VOL.  II. 


82 


ORGANIC    CHEMISTRY 


The  total  world's  production  was  about  12,000,000  tons  in  1894,  the  output  in  succeeding 
years  being  shown  in  the  note.1 

1  Output  of  crude  petroleum  (in  thousands  of  tons) : 


1900 

1905 

1910 

1912 

-1913 

1915 

1916 

United  States 

12,000 

20,000 

27,451 

29,663 

32,315 

40,760 

43,611 

Russia  .... 

9000 

7,969 

9,557 

9,265 

9,246 

9,949 

10,556 

Dutch  East  Indies  . 

800 

1,126 

1,495 

1,520 

1,534 

1,793 

1,910 

Galicia  .          .          .      '  . 

700 

855 

1,700 

1,180 

1,087 

602 

940 

Roumania 

350 

641 

1,352 

1,806 

1,885 

1,744 

1,493 

British  India 

300 

600 

818 

900 

1,000 

1,189 

1,231 

Japan    .... 

120 

195 

270 

250 

250 

452 

434 

Canada 

— 

92 

60 

— 

— 

31 

28 

Germany 

59 

81 

145 

140 

130 

144 

144 

Italy      .... 

23, 

6 

7 

7 

6 

6 

7 

Italy  (importation) 

63 

85 

113 

115 

111 

98 

Peru      .... 

— 

54 

140 

-  —  - 

— 

362. 

369 

Mexico  .... 

— 

— 

1,600 

2,100 

3,000 

4,771 

5,628 

Trinidad 

,  —  . 

— 

— 

.  —  . 

— 

— 

— 

Various  other  countries    . 

78 

85 

673 

2,375 

3,350 

— 

— 

World's  output 

23,000 

31,000 

43,500 

50,798 

60,000 

66,880 

— 

In  1913,  63-8  per  cent,  of  the  total  production  of  petroleum  was  due  to  the  United  States, 
18-2  per  cent,  to  Russia,  5-9  per  cent,  to  Mexico,  3-7  per  cent,  to  Roumania,  3  per  cent,  to  the 
Dutch  East  Indies,  2-1  per  cent,  to  Galicia,  and  1-9  per  cent,  to  British  India. 

Some  of  the  Galician  wells  are  1200  metres  deep  and  one  as  much  as  1490  metres. 
Great  Britain  imported  4269  tons  of  crude  petroleum  in  1909  and  674  tons  in  1910,  besides 
528,545  tons  of  refined  petroleum  (£2,280,000)  in  1909  and  500,000  tons  in  1910. 

In  Germany  the  output  of  145,000  tons  in  1910  was  furnished  mainly  by  Hanover,  next  in 
order  being  Alsace  (33,500  tons).  Germany  imported  983,500  tons  of  petroleum  (31,500  of  the 
crude  product,  which  was  refined  in  Germany)  in  1909,  1,150,000  tons  in  1910  and  989,000  tons 
in  1911. 

In  Alsace  (at  Pechelbronn)  350,000  tons  of  petroleum  were  extracted  in  1913  from  wells 
70  to  150  metres  deep,  the  cost  of  extraction  being  about  32s.  per  ton  of  the  crude  product. 

In  the  United  States  the  capital  invested  in  147  petroleum  refineries  in  1909  amounted  to 
£36,400,000.  The  output  in  California  has  almost  doubled  since  1908.  The  production  of 
220,200,000  barrels  (of  131  kilos)  in  1912  was  furnished  by  :  Oklahoma,  52,000,000;  Illinois, 
28,000,000;  Louisiana,  10,000,000;  Southern  Virginia,  11,800,000;  Texas,  10,500,000;  Ohio, 
8,500,000;  Pennsylvania,  8,000,000;  Indiana,  1,200,000;  Kansas,  1,300,000.  The  output 
from  the  new  borings  at  Caddo,  near  Shreveport  (Louisiana)  was  3358  barrels  (of  150  litres) 
in  1906  and  about  7,000,000  barrels  in  1911 ;  the  borings  are  as  much  as  700  metres  deep  and 
some  yield  25,000  to  70,000  barrels  (density  0-815)  per  day. 

In  1911  the  United  States  exported  4,000,000  tons  of  petroleum  (£12,200,000)  and  in  1912, 
6,500,000  tons. 

To  transport  petroleum  from  Baicoi  to  Costanza,  the  Roumanian  Government  in  1912 
projected  the  construction  of  a  pipe-line  300  kilometres  in  length,  to  cost  £720,000.  The  number 
of  companies  connected  with  the  petroleum  industry  was  59,  but  only  one-half  of  this  number 
were  successful.  The  output  in  1911  was  furnished  by  :  the  Prahova  district,  1,440,765  tons; 
Dambovitza,  88,971 ;  Buzen,  68,981,  and  Bacau,  26,402  tons. 

The  Roumanian  refineries  treated  in  1903  314,718  tons  of  crude  petroleum,  and  in  1904 
391,387  tons,  which  yielded  62,218  tons  of  benzine,  109,510  tons  of  lighting  oil,  30,214  tons  of 
mineral  oils,  and  173,661  tons  of  residues.  In  1909  Roumania  exported  420,000  tons  of  petroleum, 
benzine  and  mineral  oils,  while  in  1910,  out  of  a  production  of  1,352,300  tons,  339,300  tons  of 
refined  petroleum  and  125,750  tons  of  benzine  were  exported. 

In  Russia  the  output  in  1912  was  560,000,000  poods  (1  pood  =  36  Ibs.)  furnished  by  :   Baku, 

415,000,000    poods;    Surachany,    31,000,000;    Grosny,    65,000,000;     Tscheleken,    12,000,000; 

Binagad,  10,000,000 ;  Maikop,  9,000,000 ;  Ferghana,  4,000,000 ;  island  of  Swiatoi,  3,000,000,  etc. 

The  importation  into  France  (about  25  per  cent,  from  Russia  and  70  per  cent,  from  the  United 

States)  is  as  follows  (tons)  : 


Crude  petroleum  . 
Refined  petroleum 


159,459 
208,960 


1914 

116,070 
182,400 


1915 

18,565 

219,400 


1916 

39,000 

248,200 


Almost  all  the  petroleum  produced  in  Italy  is  obtained  from  Montechino,  that  furnished  by 
Velleia  continually  diminishing  in  amount.  Up  to  1907  the  imports  into  Italy  were  derived 
to  the  extent  of  two-thirds  from  the  United  States,  one-fourth  from  Russia,  and  only  a  little  from 
Roumania,  but  after  the  establishment  of  new  commercial  treaties  these  proportions  underwent 
marked  change,  Roumania  alone  supplying  29,000  tons  in  1909.  Further  alterations  followed 
readjustments  in  the  customs'  duties. 

The  Argentine  imported  petroleum  to  the  value  of  £400,000  from  the  United  States  in  1909, 
the  imports  into  Brazil,  also  from  the  United  States,  being  valued  at  £1,320,000  in  the  same 
year. 


TESTS    FOR    LIGHTING    OIL  83 

The  consumption  of  petroleum  for  lighting  purposes  by  different  countries  is  quite 
different  proportionately  from  the  production,  as  is  shown  in  the  following  Table,  which 
gives  the  mean  consumption  in  kilos  per  inhabitant  in  1904  and  in  1911 : 

Annual  consumption 
per  inhabitant. 

1904!  1911. 

United  States  ....  25-21  30 

Germany 16-72  11-6 

England 11-84 

France 8-22  fc 

Russia  (140,000,000  inhabitants)         .  7-51 

Japan 6-65 

Belgium  .....  20-7 

Roumania       .....  4-50 

Denmark         .....  24-4 

Austria-Hungary     ....  4-31  — 

Norway 23-3 

Italy 2-21 

Greece    ......  1-8 

India  (300,000,000  inhabitants)          .  1-7 

Spain 1-6 

China  (300,000,000  inhabitants)          .  0-85 

Holland 29 

The  units  of  measure  of  petroleum  in  different  countries  have  already  been  given  on 
p.  65. 

In  view  of  the  enormous  and  increasing  consumption  of  petroleum,  it  may  be  interesting 
to  know  how  much  longer  the  known  stock  of  petroleum  in  the  earth  will  last.  According 
to  the  calculations  made  in  1909  by  the  Geological  Survey  Office,  the  known  deposits 
of  petroleum  would  last  until  1990  if  the  annual  consumption  remained  at  its  present 
amount,  but  if  the  consumption  increases  in  the  same  proportion  as  it  has  been  doing 
during  the  last  few  years,  the  deposits  will  be  exhausted  in  1935.  Account  must,  however, 
be  taken  of  the  new  sources  discovered  every  year  and  of  the  fact  that  many  regions  still 
remain  to  be  explored. 

The  price  of  rectified  petroleum  1  at  Batoum  before  the  war  was  about  Is.  2d.  per  quintal 

1  Tests  for  Lighting  Petroleum.  A  good  petroleum  is  limpid  and  colourless,  does  not  turn 
brown  with  sulphuric  acid  (sp.  gr.  1-53),  and  has  a  specific  gravity  of  0-820  to  0-825  (Russian) 
or  0-780  to  0-805  (American);  the  specific  gravity  is  determined  with  a  hydrometer  at  15° 
(corrected  by  0-0007°  for  each  degree  of  temperature)  and  referred  to  water  at  4°.  It  should 
not  have  an  acid  reaction  ;  when  10  c.c.  of  the  petroleum  is  dissolved  in  a  mixture  of  alcohol 
and  ether  previously  rendered  neutral  to  phenolphthalein,  an  immediate  violet  coloration  should 
be  produced  on  addition  of  a  single  drop  of  N/10  alcoholic  caustic  soda.  When  subjected  to 
fractional  distillation  in  the  Engler  flask  (p.  75)  it  should  not  yield  products  distilling  below 
110°,  only  5  per  cent,  or  at  most  10  per  cent,  up  to  150°,  and  less  than  10  per  cent,  or  at  most 
15  per  cent,  above  330°;  in  the  distillation  products  the  difference  in  specific  gravity  between 
Russian  and  American  petroleums  is  increasingly  marked.  American  petroleum  is  distinguished 
from  the  Russian  (see  pp.  70  et  seq.)  also  with  the  refractometer  (see later :  Oils  and  Fats),  and  by 
the  different  solubilities  of  the  fractions  of  equal  specific  gravity  in  a  mixture  of  chloroform  and 
aqueous  alcohol  (Riche-Halphcn  test).  This  test  is  carried  out  as  follows  :  Of  each  fraction 
with  specific  gravity  higher  than  0-760,  4  grams  is  weighed  into  a  beaker,  and  from  a  burette 
a  mixture  in  equal  parts  of  anhydrous  chloroform  and  93  per  cent,  alcohol  is  run  in  until  the 
turbidity  first  formed  suddenly  disappears  : 

Density  ....    0-760   0-770   0-780   0-790   0-800   0-810   0-820   0-830   0-850   0-880 
American  petroleum  (cubic 

centimetres  solvent)      .    4-3       4-6       5-2        5-9       6-6       7-7       9-5      11-3 
Russian  petroleum   (cubic 

centimetres  solvent)      .    4-0       3-8       4-1        4-2       4-0       4-2       4-5       5-0        6-4      11-9 

Italian  petroleums  behave  like  the  Russian,  but  this  reaction  does  not  serve  to  distinguish 
between  the  other  European  petroleums  (Utz,  1905). 

The  viscosity  determined  with  the  Engler  viscometer  (see  later :  Mineral  Oils )  should  not  be 
greater  than  1-15  at  20°.  The  luminosity  is  determined  with  the  Bunsen  photometer  (p.  63) 
and,  in  general,  3-5  to  5  grams  are  consumed  per  candle-hour. 

The  determination  of  the  temperature  at  which  a  petroleum  gives  off  inflammable  vapours, 


84 


ORGANIC    CHEMISTRY 


(220  Jbs. ),  and  the  transport  to  Genoa  Is.  5d.,  and,  making  allowance  for  all  taxes,  Russian 
petroleum  costs  at  Genoa  16s.  per  quintal,  including  the  cask;  the  American  costs  16s.  \0d., 
and  at  the  present  time  Russian  petroleum  is  beginning  to  oust  the  American  product  from 
the  European  markets.  In  the  free  port  of  Hamburg,  Russian  and  American  petroleums 
cost  16s.  lOd.  per  quintal  in  1879,  13s.  Id.  in  1890,  and  14s.  9JfI  in  1904. 


TREATMENT   OF  CRUDE   BENZINE  - 

The  portion  of  crude  petroleum  distilling  below  150°  forms  crude  benzine,  which  may 
be  separated  by  fractional  distillation  into  various  qualities  for  different  commercial  uses 
(see  p.  J5). 

The  heat  of  evaporation  of  benzines  boiling  up  to  50°  is  81-14  cals.,  of  those  boiling  at 
100°,  75-93  cals.,  and  of  those  boiling  at  130°,  71-26  cals.  The  calorific  value  varies  from 
10,500  to  11,500  cals. 

is  of  great  importance,  and  in  order  to  obtain  concordant  results,  the  Abel  apparatus  modified 
by  Pensky  (Figs.  93  and  94)  is  employed  in  all  laboratories.  The  petroleum  to  be  examined  is 
placed  in  a  brass  receiver,  O,  up  to  the  level-index,  h ;  the  cover,  D  8,  carries  a  thermometer,  t, 


FIG.  93. 


FIG.  94. 


which  dips  into  the  petroleum,  and  a  clockwork  mechanism,  T  l>,  which,  when  released  (by  a 
lever,  h),  opens  automatically  a  small  window  in  the  cover;  at  the  same  instant  a  small  oil-flame 
passes  through  the  window  and  is  immediately  withdrawn,  the  window  then  closing.  The 
petroleum  receiver  is  surrounded  by  an  air-chamber,  A,  which  is  heated  to  55°  in  the  reservoir, 
W,  regulated  by  the  thermometer  tz.  For  every  0-5°  increase  of  temperature  of  the  petroleum, 
the  spring  is  released,  this  being  continued  until  the  flame  ignites  and  explodes  the  mixed  petro- 
leum vapour  and  air.  The  slight  explosion  sometimes  extinguishes  the  flame.  The  temperature 
shown  at  this  moment  by  the  thermometer  ^  is  that  of  inflammability  (flash-point),  which  is, 
however,  influenced  by  the  atmospheric  pressure  and  should  be  corrected  by  -f-  0-035°  for  every 
mm.  of  pressure  above  760  mm. 

In  Italy,  Germany,  and  Austria  the  sale  of  petroleum  for  lighting  purposes  is  prohibited 
if  it  shows  a  flash-point  below  21°  in  the  Abel  apparatus;  otherwise  explosive  vapours  could 
be  formed  in  ordinary  lamps,  even  at  30°  or  32°,  which  would  be  dangerous.  A  petroleum 
inflammable  at  above  60°  (Abel)  cannot  be  used  for  lamps. 

A  rough-and-ready  test  to  detect  if  a  petroleum  is  dangerous  consists  in  pouring  a  little 
into  a  glass  and  throwing  into  it  a  lighted  match ;  if  the  latter  is  extinguished,  the  petroleum 
is  safe. 

The  illuminating  power  is  determined  with  the  Lummer  and  Brodhun  photometer  (see 
Fig.  77,  p.  63).  To  determine  the  moisture  or  water,  which  does  not  separate  well  in  the  distilla- 
tion of  certain  Calif ornian  petroleums,  Robert  and  Fraser  (1910)  proposed  adding  calcium 
carbide  and  measuring  the  quantity  of  acetylene  formed,  this  depending  on  the  amount  of 
water  present. 


BENZINE  85 

The  crude  benzine  is  redistilled  in  small  horizontal  or  vertical  boilers,  usually  heated 
by  superheated  steam  either  in  a  jacket  or  in  closed  coils  inside  the  boiler,  the  condensed 
water  being  collected  outside  the  boiler. 

When  there  are  many  volatile  products,  an  apparatus  similar  to  that  used  in  the  rectifica- 
tion of  spirit  is  employed  (see  chapter  on  Alcohol ) ;  the  heating  is  effected  by  means  of  iron 
(not  copper)  coils,  through  which  steam  passes,  and  the  dephlegmation  is  carried  out 
first  with  water  and  then  with  air.  Such  a  system  of  rectifying  columns  is  to-day  in  general 
use,  and  the  condensation  of  the  vapours  and  the  cooling  of  the  condensed  benzine  are 
effected  by  the  crude  benzine,  which  is  thus  fractionated  and  fuel  at  the  same  time 
economised. 

A  special  apparatus  for  condensation  and  rectification,  devised  by  Veith,  consists  of 
five  iron  double-walled  cylinders  (with  water-circulation),  connected  in  series  and  ter- 
minating in  a  sixth  cylinder  containing  a  coil  with  many  turns  for  the  condensation  of 
the  vapour  from  the  preceding  cylinder.  The  coil  is  cooled  by  ice  and  cold  water,  which 
then  passes  successively  into  the  jackets  of  the  other  five  cylinders  and  gradually  becomes 
heated.  These  five  cylinders  are  three-fourths  full  of  pure  iron  turnings  free  from  oil. 
The  vapours  from  the  boiler  in  which  the  benzine  is  distilled  pass  through  cylinders  1  to  5, 
in  each  of  which  that  part  condenses  which  is  liquefied  at  the  temperature  of  the  water 
circulating  in  the  jacket. 

The  least  volatile  products  condense  in  the  first  cylinder  and  the  most  volatile  ones  in  the 
final  coil.  At  the  bottom  of  each  cylinder  is  a  pipe  with  a  tap  communicating  with  a  tank. 

The  apparatus  for  distilling  and  rectifying  benzine  are  so  constructed  that  the  vapour 
above  the  boiling  liquid  which  is  mixed  with  air  is  separated' from  the  liquid,  e.  g.,  by  metal 
gauze,  so  that  in  case  of  fire  or  explosion  the  liquid  does  not  ignite. 

Baku  petroleums  give  only  0-2  per  cent,  of  benzine,  and  those  of  Grosny  (Russia)  about 
4-5, per  cent.  In  1902,  341,000  tons  of  naphtha  were  distilled  at  Grosny,  14,000  tons  of 
benzine  (about  4  per  cent.)  being  obtained.  Pennsylvanian  petroleums  give  up  to  12  per 
cent,  of  benzine,  and  those  from  Campina  (Roumania)  3  to  5  per  cent. ;  a  petroleum  from 
Anapa  (Caucasus)  gave  28  per  cent.  Italian  petroleums  from  Emilia  yield  30  to  35  per 
cent,  of  benzine. 

After  the  fractional  distillation  of  the  benzine  the  separate  portions  are  often  refined 
by  treatment  with  concentrated  sulphuric  acid  mixed  with  0-2  per  cent,  of  potassium 
dichromate  and  0-01  per  cent,  of  lead  oxide.  Fuming  sulphuric  acid  also  gives  good 
results,  but  animal  charcoal  and  magnesium  hydrosilicates  are  not  very  satisfactory. 
The  treatment  is  carried  out  in  closed  vessels  with  mechanical  stirrers  (the  use  of  compressed 
air  being  inapplicable  here),  similar  to,  but  smaller  than,  those  used  for  refining  petroleum 
(see  Fig.  88,  p.  78).  After  removal  of  the  acid,  the  benzine  (not  stirred)  is  treated  with  a 
spray  of  water,  which  is  then  withdrawn  from  below.  The  benzine  is  next  mixed  for  some 
minutes  with  1  to  2  per  cent,  caustic  soda  solution  which  is  decanted  off,  two  washings 
with  water  then  following.  In  some  works  a  single  refining  of  the  crude  benzine,  prior  to 
rectification,  is  preferred,  counter- current  apparatus  in  series  effecting  continuous  refining. 

The  benzines  obtained  by  destructive  distillation  according  to  the  cracking  process 
(see  pp.  33  and  87)  cannot  be  refined  by  means  of  sulphuric  acid,  since  they  are  rich  in 
unsaturated  hydrocarbons,  which  give  considerable  heating  with  the  acid.  Such  benzines 
are  of  less  commercial  value  than  ordinary  benzines,  to  which  they  are  added  in  small 
proportions. 

Benzine  is  produced  mainly  at  Baku  and  in  Pennsylvania,  but  some  is  refined  in  Germany 
and  large  quantities  are  sent  to  Europe  from  the  East  Indies — from  Java,  Sumatra,  and 
Borneo ;  Galicia  and  Roumania  also  yield  large  quantities. 

Commercial  benzines  are  of  various  qualities,  and  as  they  consist  of  mixtures  of  different 
hydrocarbons,  they  have  no  well-defined  characters,  their  densities  and  boiling-points 
varying  between  certain  limits  established  by  commercial  usage  and  depending  on  the 
origin  of  the  product.  Thus,  American  automobile  benzines  (petrols)  have  the  sp.  gr. 
0-695  to  0-705,  and  the  b.-pt.  60°  to  100°,  whilst  for  Indian  benzines  the  sp.  gr.  is 
0-705  to  0-715  and  the  b.-pt.  65°  to  120°.  It  would  be  more  rational  to  lay  down  the 
rule  that  the  first  drop  should  not  distil  below  60°  and  the  last  drop  not  above  100°  (or  120° 
for  Indian  benzine),  and  that  at  95°  (105°  for  Indian)  at  least  95  per  cent,  should  distil, 
and  that  at  100°  (or  120°)  not  more  than  1  per  cent,  of  residue  should  remain. 

Rational  rectification  of    crude  petroleum   benzines  yields  the  following   products. 


86  ORGANIC    CHEMISTRY 

Rhigolene  (see  p.  37),  used  sometimes  as  a  solvent  and  as  an  anaesthetic,  has  the  sp.  gr. 
0-600  to  0-630  and  the  b.-pt.  about  35°  (more  volatile  products  form  cymogen),  and  consists 
mostly  of  pentane  and  isopentane.  Gasolene  has  the  sp.  gr.  0-630  to  0-666,  boils  at  40°  to 
50°,  and  contains  hexane  and  some  of  its  isomerides ;  it  serves  to  carburet  the  feed-air  for 
special  lamps  and  in  some  cases  as  a  solvent.  Petroleum  ether  contains  pentane,  hexane, 
and  higher  hydrocarbons,  boils  at  about  50°  to  60°,  has  the  sp.  gr.  0-660  to  0-670  (in  Russia 
and  America  it  is  divided  into  various  qualities  boiling  between  50°  and  80°),  and  is  soluble 
in  twice  its  volume  of  alcohol-ether  and  also  in  chloroform  and  carbon  disulphide;  it 
dissolves  fats,  resins  and  rubber  and  is  also  used  to  carburet  air ;  the  good  qualities  do  not 
colour  an  equal  volume  of  stilphuric  acid  when  shaken  with  it;  if  adulterated  with  tar 
benzene,  it  emits  an  odour  of  bitter  almonds  when  shaken  with  a  mixture  of  equal  volumes 
of  concentrated  nitric  and  sulphuric  acids.1  Benzine  for  removing  spots  boils  at  70°  to  90° 
and  has  the  sp.  gr.  0-700  to  0-720;  if  too  volatile,  it  leaves  a  ring  on  the  fabric  in  place  of 
the  spot.  Benzine  for  cleaning  has  the  sp.  gr.  0-725  to  0-730  and  distils  completely  below 
100°  (otherwise  it  imparts  an  unpleasant  odour  to  the  fabric).  Solvent  benzine  is  used  to 
extract  fats  from  industrial  products  (wool,  bones,  etc. )  and  also  alkaloids ;  the  different 
qualities  boil  between  80°  and  150°  (sp.  gr.  0-710  to  0-735).  American  heavy  engine  benzine 
has  the  sp.  gr.  0-735  to  0-755,  and  the  Indian  variety,  0-750  to  0-770;  the  more  expensive 
automobile  benzine  is  sometimes  adulterated  with  this  cheaper  product,  especially  for 
motor  lorries.  Benzine  to  replace  oil  of  turpentine  is  used  for  paint  and  has  a  sp.  gr. 
sometimes  as  high  as  0-800. 

The  consumption  of  benzine  in  the  various  countries  of  Europe  amounted  in  1908  to  : 
115,000  tons  in  Germany,  130,'000  tons  in  France,  100,000  tons  in  England,  10,000  tons 
in  the  Netherlands,  110,000  tons  in  Russia,  20,000  tons  in  Roumania,  10,000  tons  in  Austria 
and  Galicia,  and  25,000  tons  in  other  countries.  The  United  States  produced  800,000  tons 
of  benzine  in  1908  and  the  Dutch  Indies  260,000.  In  succeeding  years  the  consumption 
increased  enormously  owing  to  the  rapid  development  of -motoring.2 

The  price  of  light  and  heavy  benzines  doubled  between  1909  and  1914  (in  Germany 
the  light  products  cost  £12  16s.,  and  the  heavy  ones  £8  per  ton  in  1909).  The  average 
consumption  per  kilometre  may  be  taken  as  180  grams  for  motor-cars  and  600  grams  for 
heavy  commercial  vehicles  (these  use  also  the  cheaper  heavy  benzines). 

TREATMENT   OF   PETROLEUM   RESIDUES 
A.  Lubricating  Oils.     7J.  Vaseline.     C.  Paraffin  Wax. 

(A)  LUBRICATING  OILS.  The  crude  petroleum  residue  remaining  in  the  boilers 
even  at  300°  (astatki  or  masut)  3  forms  a  brownish  black  mass  with  a  greenish  reflection, 

1  A  more  certain  test  is  the  very  sensitive  indophenine  reaction,  due  to  thiophene  (q.  v. ), 
which  is  always  present  in  benzene  from  tar. 

2  France  imported  the  following  amounts  of  petroleum  benzine  (especially  from  the  United 
States)  :    170,000  tons  in  1913,  172,000  in  1914,  214,000  in  1915,  and  325,000  in  1916. 

The  output  of  benzine  in  the  United  States  was  12,000,000  barrels  (of  159  litres)  in  1909, 
while  in  1913  that  for  motoring  alone  amounted  to  about  17,000,000  barrels. 

The  quantities  of  crude  benzine  imported  by  Germany  (one -half  from  the  Dutch  Indies  and 
the  rest  from  Austria,  Roumania,  and  Russia)  were  :  133.813  tons  in  1909  and  188,000  in  1911, 
the  pure  benzine  imported  being  5864  tons  in  1909  and  7387  in  1910.  The  output  in  Germany 
was  133,765  tons  in  1910,  and  165,058  tons  (£1,440,000)  in  1911. 

The  Italian  production  and  importation  of  benzine  were  as  follows  (tons)  : 

1905  1910  1912  1913  1914  1915  191C  1917 

Production  .       —         2,000       4,000       3,000       2,000       2,000         2,000          — 

•    Importation         .    3,000      11,000     23,000     30,000     41,000     54,000      109,000      109,000 

Roumania  produced  231,000  tons  of  benzine  in  1910,  and  the  Argentine  imported  benzine 
to  the  value  of  £344,000  in  1909. 

3  Masut  contains,  on  the  average,  87-5  per  cent.  C,  11  per  cent.  H,  and  1-5  per  cent.  0;   it 
has   a   mean   sp.    gr.    of    0-91,    an   ignition   temperature   of    110°,   and    a    calorific    value   of 
10,700  cals.     When  used  as  a  fuel  it  is  gasified,  the  vapours,  mixed  with  compressed  air,  burning 
completely;   it  is  often  burnt  directly  after  pulverisation  with  compressed  air  or  steam. 

In  view  of  the  great  calorific  value  of  petroleum  residues  and  their  increasing  production, 
new  outlets  have  been  sought  for  them ;  they  should  have  a  great  future  as  a  substitute  for  coal 
in  the  heating  of  boilers,  steam-engines,  ships,  etc. 

As  has  been  already  stated,  however,  this  use  of  it  is  diminishing  in  Russia,  although  con- 
tinually extending  in  the  United  States.  In  Italy  attempts  have  been  made  (1911)  to  burn 


CRACKING 


87 


dense  and  sometimes  semi-solid  at  ordinary  temperature,  and  often  with  a  burnt,  faintly 
creosotic  smell;  it  has  the  sp.  gr.  0-900  to  0-950  and  the  coefficient  of  expansion 
0-00091 ;  that  of  Baku  contains  no  paraffin  wax  and  hence  does  not  freeze,  and  gives  inflam- 
mable vapour  even  at  120°  to  160°.  When  these  residues  are  discharged  from  the  boiler, 
in  order  to  cool  them  and  so  prevent  them  taking  fire  they  are  passed  through  the  tubes 
which  serves  to  heat  the  crude  petroleum  before  introducing  it  into  the  boiler.  At  Baku 
the  residues,  which  form  almost  two-thirds  of  the  crude  naphtha,  are  largely  used  as  a 
fuel  for  the  distillation  vessels  and  also  for  locomotives  and  marine  engines,  the  calorific 
power  being  9700  to"  10,800  cals.  and  1  kilo  being  able  to  evaporate  as  much  as  14  to  15 
kilos  of  water. 

Utilisation  of  a  great  part  of  these  residues  was  commenced  after  the  first  American 
and  Scotch  samples  (from  shale  oils)  were  exhibited  at  the  International  Exhibition  at 
Paris  in  1867.  In  Russia  enormous  quantities  of  residues,  of  almost  no  commercial  value, 
accumulated  every  year.  Their  utilisation  was  initiated  in  1873  at  Balachna  (near  Nijni 
Novgorod)  and  later  at  Baku  by  the  Ragosin  process  for  preparing  the  best  lubricating 
oils  (those  of  Baku  are  highly  valued)  by  distilling  the  residues  by  means  of  superheated 
steam,  so  as  to  avoid  the  formation  of  empyreumatic  odours.1 

The  distillation  of  these  oils,  and  also  that  of  the  oils  transuding  during  the  refining 
of  paraffin  wax  (see  later),  is  now  carried  out  in  long  horizontal  boilers,  since  in  vertical 
ones — which  were  used  at  one  time — the  vapours,  in  contact  with  the  heated  walls,  give 
products  of  profound  decomposition  and  of  bad  odour.  Direct-fire  heating  may  be  partly 

it,  after  pulverisation,  directly  under  boilers,  and  it  might  be  used  advantageously  if  it  did 
not  cost  at  the  factory  more  than  about  £2  8s.  per  ton,  coal  giving  8000  cals.  costing  £1  Ss. ;  the 
cost  of  transport  is,  however,  excessive,  increasing  the  price  from  8s.  to  12s.  at  the  refinery  to 
£2  8s.  in  Italy.     The  Customs  duty  (Italy)  is  only 
Is.  Td.  per  ton. 

The  heavy  oils  extracted  from  petroleum  residues 
are  largely  used  for  special  engines  of  the  Diesel 
type. 

1  "  Cracking  "  Process.  In  some  cases  it  is 
convenient  to  convert  the  heavy  mineral  oils  (and 
also  the  masut)  into  petroleum  for  lighting,  use  being 
made  of  the  process  of  cracking.  This  is  based  on 
the  fact,  established  in  1872  by  Thorpe  and  Young, 
that,  when  the  vapours  of  heavy  petroleums  are 
superheated,  they  yield  gaseous  hydrocarbons  (6  to 
8  per  cent.)  usually  poorer  in  hydrogen  (ethylene 
series)  and  lighter  liquids  which  may  be  used  as 
second-quality  petroleum.  The  operation  is  carried 
out  in  a  vertical  boiler  (Fig.  95),  placed  in  a  furnace 
so  that  its  walls  are  strongly  heated  by  the  hot 
fumes  circulating  round  them.  The  boiler  is  not 
completely  filled  with  masut,  so  that  the  vapours 
evolved,  coming  into  contact  with  the  red-hot  walls 
above  the  liquid,  are  decomposed ;  after  separation 
in  a  dephlegmator  of  the  heavy  oil  carried  over,  the 
vapours  are  progressively  liquefied  in  ordinary  con- 
densers or  refrigerators,  yielding  lamp  oil,  benzine,  etc.,  whilst  the  remaining  gas  is  used  for 
heating  or  for  gas-engines.  A  mineral  oil  from  Ohio  treated  by  this  process  gave  the  following 
products  :  25  per  cent,  of  benzine  (sp.  gr.  "0-650  to  0-745),  33  percent,  of  lighting  petroleum 
(sp.  gr.  0-800  to  0-840),  10  per  cent,  of  light  paraffin  oils  for  burning  (sp.  gr.  0-854  to  0-859), 
31  per  cent,  of  solid  paraffin  wax  and  paraffin  oil  (sp.  gr.  0-870  to  0-925),  and  3  per  cent,  of  coke 
and  loss. 

Manufacture  of  Benzene  from  Naphtha.  Attempts  in  this  direction  had  already  been  made 
as  early  as  1875,  and  later  Ragosin  and  Nikiforow,  Krey,  Laing,  Dewar,  and  Redwood  attacked 
the  problem,  but  without  practical  success.  Recently  Nikiforow  appears  to  have  succeeded, 
and  he  has  devised  a  plant  for  treating  2400  tons  of  crude  naphtha  and  producing  262  tons  of 
benzene.  He  subjects  the  naphtha  to  two  distillations  under  different  pressures,  in  a  retort 
first  at  500°  and  then  at  1000°.  In  this  way  38  per  cent,  of  tar  containing  50  per  cent,  of 
aromatic  compounds  is  obtained,  together  with  an  abundant  supply  of  gas  which  serves  for 
heating,  lighting,  and  power  purposes.  After  redistillation  and  rectification  of  the  first  of  these 
products,  a  final  yield  of  12  per  cent,  of  benzene  and  toluene  is  obtained,  3  per  cent,  of  naph- 
thalene, 1  per  cent,  of  anthracene,  and  various  secondary  products.  Benzene  thus  prepared 
will  apparently  cost  £10  per  ton  and  the  aniline  oil  (used  in  dyeing)  obtainable  from  it  would 
cost  about  one-half  as  much  as  that  on  the  market  in  Russia.  J.  Hausmann  (Ger.  Pat.  227,178, 
1909)  also  obtains  benzene  and  its  derivatives  by  passing  the  vapours  of  mineral  oil  into  red-hot 
tubes,  and  into  contact  with  catalytic  agents  (oxides  of  iron,  lead,  and  cerium,  sulphate  of  iron, 
etc.). 


FIG.  95. 


88 


ORGANIC    CHEMISTRY 


used  in  conjunction  with  internal  heating  by  superheated  steam  at  220°,  and  the  distillation 
is  facilitated  by  carrying  it  out  in  a  vacuum  (see  p.  77). 

Fig.  96  shows  the  plant  used  by  Nobel  Brothers  at  Baku.     The  condensation  is  effected 
in  long,  parallel,  slightly  slanting  pipes,  d,  dv  dz  (40  to  50  cm.  in  diameter),  communicating 


FIG.  96. 

alternately  at  the  ends.  The  first  of  these  is  cooled  by  air  alone,  the  second  by  water,  and 
the  third  by  very  cold  water  that  circulates  in  a  coil;  H  is  an  exhaust-pump.  At  the 
bottom  of  each  of  these  pipes  is  a  discharge  pipe  for  the  mineral  oil  coiidensates,  which 
pass  to  water-separators ;  thus  three  qualities  of  oil  are  obtained  in  three  separate  tanks  : 
20  to  25  per  cent,  of  lamp  oil,  sp.  gr.  below  0-890;  6  to  10  per  cent,  of  spindle  oil, 

sp.  gr.  0-890  to  0-900;  25  to  30  per 
cent,  of  engine  oil,  sp.  gr.  0-900  to 
0-920;  3  to  4  per  cent,  of  cylinder 
oil,  sp.  gr.  0-925 ;  3  per  cent,  of  tar ; 
and  5  per  cent,  of  loss.  The 
quantity  of  steam  consumed  varies 
from  100  to  150  per  cent,  of  the 
amount  of  oil  distilled  and  the 


Section  J.fC. 


FIG.  97. 


quantity  of   masut  treated  every  twenty-four  hours  corresponds  with  about  double  the 
volume  of  the  boilers. 

A  somewhat  different  apparatus,  which  has  also  given  good  results  for  the  distillation 
of  tar  and  of  its  heavy  oils,  is  that  made  by  the  firm  of  Hirzel  in  Leipzig.  The  large  boiler, 
BV,  with  a  convex  base  (Figs.  97  and  98)  is  divided  longitudinally  by  a  metal  partition, 
1,  which  allows  the  two  halves  of  the  boiler  to  communicate  at  the  end,  7 ;  the  distillation 
products  enter  at  the  tube  4,  connected  with  the  horizontal  pipe  5,  from  which  the  liquid 
descends  to  the  bottom  of  the  first  half  of  the  boiler  along  the  tubes  6 ;  the  superheated 


LUBRICATING     OILS  89 

steam  enters  by  the  tube  3,  which  is  forked  half-way  down  the  boiler  and  connects  with 
a  battery  of  horizontal  perforated  pipes,  2,  running  along  the  bottom  of  the  boiler.  The 
liquid  moves  slowly  in  a  comparatively  thin  layer  from  the  first  to  the  second  half  of  the 
boiler,  passing  through  the  space  7,  and  issuing  at  the  tube  8;  the  vapours  are  collected 
in  the  dome,  W,  containing  perforated  discs  to  condense  the  drops  carried  over  with  the 
vapours,  the  latter  proceeding  through  the  tube  a  to  the  rectification  or  fractional  distilla- 
tion apparatus.  In  1911  the  Hirzel  apparatus  was  also  used  by  a  large  Italian  firm  of 
metallurgical  coke  manufacturers  and  tar  distillers. 

All  these  crude  mineral  lubricating  oils,  after  being  freed  from  moisture  by  heating, 
are  refined  by  prolonged  shaking  in  apparatus  similar  to  that  shown  in  Fig.  110  with  5  to 

10  per  cent,  of  concentrated  sulphuric  acid  (containing  not  more  than  0-01  per  cent,  of 
nitrous  acid)  and,  after  decantation  of  the  black  acid,  with  0-4  to  0-8  per  cent,  of  a  con- 
centrated caustic  soda  solution  (23°  Be.),  just  as  with  lamp  oil,  but  at  60°  to  65°,  this  being 
followed  by  washing  with  hot  water.     The  largest  proportions  of  the  reagents  are  used 
with  the  denser,  darker  oils,  the  stirring  being  then  effected  with  mechanical  stirrers  instead 
of  with  air.     In  these  refining  operations  3  to  5  per  cent,  of  the  mineral  oil  is  lost  during 
the  acid  treatment  and  4  to  6  per  cent,  during  the  alkaline  treatment.     The  residues  in 
the  boilers,  if  they  are  not  solid  coke,  but  pasty,  are  dissolved  in  benzene  as  a  black  varnish 
for  iron,  or  are  used  as  an  adhesive  in  the  manufacture  of  briquettes  from  coal-dust,  or 
as  a  fuel. 

According  to  Ger.  Pats.  161,924  and  161,925,  it  is  proposed  to  treat  crude  mineral 
oils  with  a  saturated  solution  of  sodium  chloride  and  carbonate,  to  blow  air  in  for  some 
time,  and  finally  to  distil  in  presence  of  an  oxide  of  manganese. 

To  render  mineral  oils  inodorous,  or  nearly  so,  they  are  treated  in  the  hot  with  formalde- 
hyde, and,  after  addition  of  alkali  or  acid  to  the  mass,  a  current  of  steam  is  passed  through 
(Ger.  Pat.  147,163).  According  to  Ger.  Pat.  153,585,  the  20  per  cent,  of  crude  mineral 

011  is  distilled  with  superheated  steam  at  180°  in  presence  of   1  per  cent,  of  aqueous  lead 
acetate  solution.     The  distillate  is  free  from  sulphur  and  forms  a  lighting  or  gas-engine 
oil;   the  residue,  after  filtration,  forms  a  denser  and  almost  odourless  lubricating  oil.     In 
some  cases  petroleum  is  deodorised  by  agitating  with  chloride  of  lime  and  a  sma,ll  quantity 
of  hydrochloric  acid,  decanting  it,  shaking  with  lime  to  fix  the  chlorine,  and  sometimes 
adding  a  little  amyl  acetate  or  essence  of  fennel ;  treatment  with  soda  lye  is  also  resorted 
to,  and,  better  still,  both  for  mineral  oils  and  petroleums,  with  sodium  peroxide. 

Latterly,  mineral  oils  soluble  in  water  have  acquired  importance  for  lubricating 
machinery,  for  greasing  textile  fibres  to  be  combed,  and  for  watering  the  streets  to 
prevent  dust.  They  are  prepared  by  the  Boleg  process  (Ger.  Pats.  122,451,  129,480, 
148,168,  155,288)  :  the  mineral  oil  is  heated  in  a  closed  vessel,  fitted  with  a  condenser, 
at  a  temperature  of  60°  to  70°  or  above  by  means  of  indirect  steam;  at  the  same  time 
finely  divided  compressed  air,  after  addition  of  a  little  caustic  soda  solution,  is  injected ; 
a  small  quantity  of  resin  soap  or  a  sulphoricinate  is  subsequently  introduced,  the  air- 
current  being  continued  meanwhile,  and  finally  the  whole  mass  is  heated  under  pressure 
in  an  autoclave. 

Emulsions  of  mineral  oils  with  water  are  obtained  by  addition  of  pyridine  or  quinoline 
bases  or  amino-acids. 

To  obtain  from  dark  mineral  oils  less  coloured  oils,  and  in  some  cases  oils  as  colourless 
as  water  (e.  g.,  vaseline  oils),  the  oil  is  passed  slowly  at  30°  to  50°  through  a  series  of  tall, 
communicating  cylinders,  sometimes  kept  hot  by  means  of  steam  jackets  (batteries  of 
tubes  arranged  in  a  system  similar  to  the  diffusors  used  for  extracting  sugar  from  beets  : 
see  chapter  on  Sugar) ,  and  charged  with  layers  of  decolorising  clay  separated  by  perforated 
discs  or  gauze  to  prevent  the  mass  from  becoming  too  compact  and  thus  hindering  the 
permeation  of  the  oil.  These  clays  are  found  more  especially  in  North  America,  but  occur 
also  in  Great  Britain  and,  in  inferior  quality,  in  other  countries ;  they  are  similar  to  fuller's 
earth,  but  the  best  is  Florida  earth,  consisting  of  aluminium  and  magnesium  hydrosilicates 
(see  Vol.  I.,  p.  738),  previously  subjected  to  slight  roasting.  The  mineral  oil  remaining 
in  the  filters  is  recovered  by  displacing  it  by  heavy  tar  oil  (very  cheap)  and  displacing 
the  latter  with  water. 

The  exhausted  fuller's  earth  may  be  regenerated  by  extracting  the  oil  it  contains  by 
means  of  benzine ;  the  latter  is  recovered  by  distillation,  and  that  remaining  in  the  earth 
by  a  current  of  steam.  After  this  treatment  the  fuller's  earth  is  heated  in  a  revolving, 


90 


ORGANIC    CHEMISTRY 


cylindrical  metal  cylinder  (like  that  used  for  cement;  see  Vol.  I.,  p.  760),  cooling  being 
effected  in  a  lower,  revolving  cylinder  sprayed  with  water.  With  each  repetition  of  this 
treatment,  the  earth  loses  in  decolorising  power. 

Decolorisation  is  also  effected  by  bone-black  or,  best  of  all,  by  residues  from  the 
manufacture  of  potassium  ferrocyanide,  which  exhibit  very  great  decolorising  power 
(50  per  cent,  more  than  American  clay) ;  owing,  however,  to  the  new  methods  of  manu- 
facturing ferrocyanide,  these  residues  are  becoming  scarcer  and  more  expensive  (they 
contain  30  to  40  per  cent,  of  animal  charcoal,  considerable  quantities  of  silica  and  silicates, 
and  a  little  ferric  oxide).  The  darker  mineral  oils  are  partly  decolorised  with  sulphuric 
acid,  sometimes  together  with  dichromate.1  In  the  case  of  certain  dark  mineral  oils, 
repeated  filtration  through  fuller's  earth  is  replaced  by  purification  with  sulphuric  acid 
and  soda,  but  this  occasions  greater  losses. 

Carts  are  often  greased  with  the  so-called  consistent  fats  obtained  by  mixing  15  to  23 
per  cent,  of  calcium  soaps  and  mineral  oils  with  1  to  4  per  cent,  of  water  (if  there  is  no 
water  the  mass  remains  liquid,  and  if  there  is  not  a  little  free  fatty  acid  emulsification 
ceases  after  a  time  and  the  calcium  soap  separates). 

REQUIREMENTS  IN  AND  ANALYSIS  OF  LUBRICATING  OILS.  Lubricating 
oils  serve  to  diminish  the  friction  between  metal  surfaces  in  motion ;  by  adhering  strongly, 
although  in  very  thin  layers,  to  these  surfaces  they  prevent  contact  between  them  and 
hence  friction  and  heating,  without  sensible  increase  of  the  resistance  owing  to  the  internal 
friction  of  the  oil.  Lubrication  is  due  partly  to  chemical  phenomena  (formation  of  metallic 
soaps)  but  more  especially  to  physical  phenomena  not  well  understood. 

Liquids  which  moisten  surfaces  (unlike  mercury)  exhibit  great  adhesive  or  capillary 
force  and  penetrate  into  the  finest  cracks.  This  capillary  force  (external  friction)  for 
thin  layers  of  oil  increases  with  diminution  of  the  radius  of  curvature,  and  is  sufficiently 
great  to  prevent  direct  contact  of  two  surfaces  between  which  the  liquid  is  interposed,  no 
matter  how  great  the  pressure.  Thus,  the  resistance  between  the  bearing  and  the  revolving 
shaft  it  supports  depends  almost  exclusively  on  the  internal  friction  of  the  lubricating  oil, 
i.  e.,  on  the  viscosity  of  the  oil.2  Of  two  oils  with  equal  viscosities,  the  preference  is  naturally 

1  For  the  thorough  decolorisation  of  vaseline  oil  the  following  operations  are  carried  out : 
(1)  Drying  or  dehydration;  (2)  treatment  with  10  to  15  per  cent,  of  fuming  sulphuric  acid  and 


FIG.  99. 


FIG.  100. 


separation  of  the  tarry  matters  formed;  (3)  neutralisation  with  caustic  soda  solution  (10°  to 
12°  Be.);  (4)  separation  of  the  alkali  and  washing  with  water;  (5)  clarification  with  4  to  5  per 
cent,  of  pure  50  per  cent,  alcohol  and  removal  of  the  milky  layer  deposited;  (6)  bleaching  with 
dry  fuller's  earth  and  subsequent  filtration. 

2  For  lubricating  oils  it  is  important  to  determine  the  viscosity  (due  especially  to  polynaph- 
thenes),  and  this  is  usually  effected  by  means  of  the  Engler  viscometer  (Figs.  99  and  100),  formed 


FLASH     POINT 


91 


given  to  the  one  containing  the  smaller  proportion  of  substances  liable  to  undergo  change 
(asphalte,  resin,  soaps,  etc.).  Even  the  best  lubricating  oils,  when  in  use,  are  subject  to 
more  or  less  marked  alteration  (oxidation,  pulverisation,  emulsification,  etc.),  which  is 
evident  especially  in  ring  lubrication  or  in  the  lubrication  of  turbines,  where  the  oil  is 
changed  at  infrequent  intervals ;  in  such  cases,  oils  of  the  highest  quality  should  be  used, 
as  replacement  is  expensive  (some  oil-boxes  contain  100  to  200  kilos  of  oil).  More  rapid 
is  the  alteration  of  lubricants  used  for  engines  or  steam- cylinders,  where  the  temperature 
is  150°  to  200°  or  even  250°,  part  of  the  oil  undergoing  decomposition  with  separation 
of  small  particles  of  coke  and  asphalte.  In  these  cases  it  is  important  to  determine  the 
flash-point  of  the  oil l  (so  that  danger  of  ignition  of  the  oil  may  be  avoided);  use  may  also 
be  made  of  the  formolite  reaction  and  of  the  reaction  with  fuming  acid  (see  p.  71). 
In  general,  where  there  is  much  pressure  the  viscous  oils  are  suitable,  and  in  other 
places  liquid  oils,  although  in  practice  mixtures  of  these  two  kinds  are  advantageously 
employed.  Oil  for  lubricating  steam  cylinders  at  high  temperatures  should  be  resistant 
to  great  heat  and  to  the  mechanical  and  chemical  action  of  steam,  and  should  not  give 
inflammable  products  at  a  lower  temperature  than  220°,  or  300°  where  superheated  steam 
is  employed ;  it  should  possess  great  adhesive  power  and  viscosity  and  should  not  contain 

of  a  brass  vessel,  A  (sometimes  gilt  inside),  provided  with  a  cover,  Alt  through  which  passes  the 
thermometer,  <j  at  the  bottom  of  the  vessel  is  a  platinum  tube,  a,  20  mm.  long  and  of  such 


FIG.  101. 


FIG.  102. 


dimensions  that  it  allows  of  the  efflux  of  200  c.c.  of  distilled  water  at  20°  in  52  to  54  sees.;  the 
aperture  can  be  closed  from  above  by  the  hard  wooden  peg,  6.  The  vessel,  A,  is  contained  in  a 
larger  one,  B,  and  the  space  between  the  two  is  filled  with  water  maintained  constantly  at  the 
desired  temperature  by  means  of  the  ring-burner,  d,  and  the  thermometer,  tv  The  dimensions 
of  the  apparatus  are  exactly  defined  and  are  shown  in  millimetres  in  the  figure.  The  mineral 
oil  is  introduced  into  A  (clean  and  dry) -up  to  the  level  indicated  by  the  three  points  (about 
240  c.c.).  When  the  temperature  of  the  oil  in  A  has  the  desired  constant  value,  the  flask  C  is 
placed  under  the  efflux  tube  and  the  peg  rapidly  removed,  the  exact  number  of  seconds  taken  to 
fill  the  flask  to  the  200  c.c.  mark  being  determined  by  a  chronometer.  The  time  required,  in 
seconds,  divided  by  the  corresponding  number  of  seconds  for  water  at  the  same  temperature 
gives  directly  the  degree  of  viscosity. 

1  The  flash-point  is  determined  by  the  Pensky -Martens  apparatus  (Figs.  101  and  102),  which 
is  analogous  to  the  Abel  apparatus  (p.  84),  but  without  the  water-bath,  being  furnished  instead 
with  a  stirrer  with  vanes,  b,  moved  by  twisting  the  metal  cord,  b',  between  the  fingers;  it  works 
similarly  to  the  Abel  apparatus,  and  the  small  flame,  E,  applied  automatically,  is  fed  by  a  .-mall 
gas  tube,  H,  and  is  relighted,  every  time  it  is  extinguished,  by  another  flame  by  its  side.  The 
thermometer,  t,  is  graduated  from  80°  to  320°,  and  the  heating  is  effected  by  the  triple  gas- 
burner,  g,  so  that  the  temperature  rises  5°  per  minute;  observations  are  made  by  releasing  the 
spring,  at  first  for  every  2°  and  later  for  every  1°  rise  of  temperature. 


92  ORGANIC    CHEMISTRY      - 

resinous  or  tarry  residues.  No  oil  resists  the  action  of  steam  at  above  350°.  The  good 
qualities,  which  are  more  or  less  dark,  are  transparent  in  the  liquid  state.  The  selection 
for  steam  cylinders  of  oils  viscous  at  ordinary  temperatures  is  unimportant,  as  they  become 
as  liquid  as  water  when  hot;  this  is  seen  from  a  comparison  of  the  following  two  mineral 
oils,  the  numbers  giving  the  viscosity  in  seconds  required  for  the  passage  of  200  c.c.  of  oil 
through  the  Engler  viscometer  (see  above). 

at  70°     at  100°     at  150°    at  170° 

Viscosity  of  sample  I  270  116  74  67 

„  II          835  226  93  73 

The  Russian  engine  oils  are  more  viscous  than  the  American,  but  the  American  cylinder 
oils  are  more  viscous  than  the  Russian.  American  oils  with  sp.  gr.  0-908  to  0-920  and 
0-844  to  0-899  have  viscosities  almost  the  same  as  those  of  the  Russian  oils  with  sp.  gr. 
0-893  to  0-900  and  0-900  to  0-923  respectively. 

The  specific  gravities  of  certain  American  and  Russian  oils  are  as  follows  : 

American  Kussian 

Axle  oil      ....  0-908-0-911  0-893-0-895 

Pale  engine  oil     .          .          .  0-920  0-903-0-905 

Dark  engine  oil   .          .          .  0-884  0-900-0-920 

Cylinder  oil         .         .         .  0-886-0-899  0-911-0-923 

At  the  foot  of  the  page  is  given  a  summary  of  the  criteria  laid  down  by  Holde  for 
various  lubricating  oils  of  good  quality  and  the  requirements  to  be  answered  by  those 
supplied  to  the  Italian  railways.1  In  Russia  special  oils  of  more  than  thirty  different  types 
are  now  prepared. 

1  (1)  Oils  for  spinning  spindles.  Clear  liquids,  viscosity  (see  Engler  viscometer),  5  to  12  at 
20°,  inflammability  (in  the  Martens-Pensky  apparatus),  160°  to  200°.  (2)  Oils  for  ice-machines 
or  compressors.  Very  fluid ;  viscosity,  5  to  7  at  20° ;  freezing-point  below  —  20° ;  inflammability, 
140°  to  180°.  (3)  Oils  for  light  engines  and  transmission,  motors,  dynamos.  Medium  fluidity, 
viscosity,  13  to  25  at  20°;  inflammability,  160°  to  210°.  (4)  Oils  for  heavy  engines  and  trans- 
mission. Dense;  viscosity,  25  to  45  to  60  at  20°;  inflammability,  160°  to  210°.  (5)  Dark 
oils  for  locomotives  and  railway  carriages.  Viscosity,  45  to  60  (summer),  25  to  45  (winter) ;  inflam- 
mability above  140°;  freezing-point,  —  5°  (summer),  —  15°  (winter).  (6)  Oils  for  steam  cylinders. 
Very  dense  or  buttery;  viscosity,  23  to  45  at  50°;  inflammability,  220°  to  315°.  For  these 
buttery  oils,  the  dropping -point  is  determined  by  the  Ubbelohde  apparatus  (p.  6).  (7)  Oils  for 
explosion  engines  (motor-cars,  etc. )  are  somewhat  different  from  those  for  steam  cylinders,  since 
the  gases  igniting  and  exploding  in  the  cylinder  of  an  internal  combustion  engine  generate  very 
high  temperatures  (1200°  to  1400°),  and  these,  added  to  the  rapid  motion  of  the  piston,  result 
in  the  combustion  of  part  of  the  lubricating  oil,  which  passes  into  the  exhaust  gases.  Such 
combustion  is  the  more  incomplete  (and  hence  gives  strong-smelling  products  instead  of 
inodorous  C02  and  H^O),  the  higher  the  proportion  of  dense,  high-boiling  point  products  present 
in  this  fraction  of  the  lubricant.  Consequently  oils  for  this  purpose  should  not  be  too  dense 
or  of  too  high  a  flash-point.  The  combustion  of  these  compounds  is  the  more  complete,  the  less 
the  proportion  of  carbon  they  contain  and  hence  the  less  oxygen  they  require  for  their  combustion, 
since  almost  all  the  air  drawn  in  by  the  engine  is  necessary  for  the  complete  combustion  or 
explosion  of  the  combustible  mixture  working  the  engine  and  insufficient  oxygen  to  bum  com- 
pletely the  part  of  the  lubricant  referred  to  results  in  the  separation  of  carbonaceous  substances 
which  foul  the  cylinder  and  cause  it  to  work  irregularly,  while  the  exhaust  gases  assume  a  bluish 
colour  and  an  unpleasant  odour.  The  addition  of  vegetable  and  animal  fatty  oils  also  pro- 
duces these  inconveniences.  F.  Schwarz  and  H.  Schluter  (1911)  found  that,  if  the  lubricating 
oil  is  shaken  with  acetone,  the  latter  dissolves  and  removes  mostly  the  denser  products  of  high 
boiling-point,  whilst  the  insoluble  portion  is  more  fluid,  and  usually  forms  an  oil  which  burns 
completely  in  internal  combustion  engines  without  carbonising  or  giving  a  disagreeable  smell. 
In  general  good  oils  for  this  purpose  are  pale  and  have  a  viscosity  of  6  to  13  at  50°  (or  25  to  65 
at  20°);  they  contain  little  paraffin  wax,  so  that  they  do  not  freeze  readily  in  winter  and  thus 
do  not  obstruct  the  "feed -pipes. 

The  authorities  of  the  Italian  railways  demand  Russian  oils,  since  these  freeze  only  below 
—  10°,  whilst  the  American  ones  solidify  at  0° ;  they  must  not  contain  water,  that  is,  they  must 
not  froth  if  heated  to  129° ;  they  must  give  no  deposit  even  after  standing  for  forty -eight  hours ; 
the  viscosity  must  be  at  least  eight  times  that  of  water;  they  should  be  perfectly  neutral  and 
should  not  contain  shale  oil,  resin  oil,  animal  or  vegetable  oil,  or  tar  oil,  as  these  lower  the  quality ; 
they  should  not  have  the  slightest  "  drying  "  properties  in  the  air  (smeared  on  glass),  or  have  a 
density  below  0-91  or  a  flash-point  below  150°  to  180°;  they  must  not  contain  more  than  10  per 
cent,  of  light  oils  distilling  below  310°;  when  shaken  with  water,  the  oil  should  separate 
immediately  without  the  water  remaining  whitish. 

With  mineral  oils  for  automobiles  it  is  important  to  test  for  resin  oils,  the  procedure  being  as 


VASELINE  93 

Mineral  oils  are  also  used  in  special  engines  to  utilise  their  high  calorific  value  (10,500 
to  11,700  cals. ).  Scherman  and  Kropf  (1908)  found  that  the  calorific  power  of  mineral 
oils  and,  to  some  extent,  that  of  petroleums  is  inversely  proportional  to  their  specific 
gravity.  Mineral  oils  are  often  used  as  insulators  in  electric  motors. 

The  origin  and  properties  of  certain  mineral  oils  are  often  related  to  their  content  of 
paraffin  wax,  the  determination  of  which  is  effected  as  described  above. 

The  acidity  is  determined  by  titrating  50  c.c.  of  the  100  c.c.  of  50  per  cent,  alcohol 
(neutralised)  shaken  up  with  10  grams  of  the  mineral  oil;  expressed  as  SO3,  it  should  be 
below  0-01  per  cent. 

It  is  sometimes  useful  to  know  if  certain  more  or  less  dark  mineral  oils  are  true  refined 
products  obtained  by  the  distillation  of  petroleum  residues  (masut,  etc.),  or  if  they  are 
merely  the  crude  residues  themselves  diluted  with  more  or  less  mineral  oil.  Charitschkofi 
(1907)  found  that  the  rise  of  temperature  on  mixing  with  concentrated  sulphuric  acid 
(Maumene  number :  see  also  chapter  on  Fats)  in  a  Beckmann  apparatus  (see  Molecular 
Weights,  Vol.  I. )  is  2-2°  to  3-5°  for  all  distilled  products  (lamp  oil  and  various  lubricating 
oils)  and  4°  to  8-5°  for  all  non-distilled  products  (crude  naphtha,  masut,  etc.).  In  certain 
cases  the  formolite  reaction  and  that  with  nitric  acid  (see  pp.  71,  91)  give  reliable 
indications. 

STATISTICS.  In  all  countries  the  consumption  of  mineral  oils  is  continually 
increasing. 

The  United  States  produced  11,000,000  barrels  of  mineral  oils  in  1909  and  exported 
5,000,000  barrels  in  1910  and  5,600,000  in  1911. 

France  imported  144,600  tons  of  mineral  oils  in  1913,  101,170  in  1914,  106,610  in  1915, 
and  170,014  in  1916,  and  exported  7937  tons  in  1913,  6579  in  1914,  and  4665  in  1915. 

Germany  imported  216,987  tons  in  1909,  236,516  in  1910,  and  260,242  in  1911,  and 
produced  85,850  tons  in  1910,  and  93,889  tons  (£680,000)  in  1911.  Before  the  war  the 
price  was  £8  to  £12  per  ton,  during  the  war  it  rose  to  £160,  and  the  Bavarian  railways 
lubricated  their  wagons  with  coal-tar  oils  suitably  prepared. 

In  1909  the  Argentine  imported  mineral  oils  to  the  value  of  £500,000,  while  the  imports 
into  Brazil  were  valued  at  £280,000  in  the  same  year. 

The  imports  into  Italy  were  :  29,250  tons  in  1905,  40,467  in  1908,  49,181  in  1910,  60,3ll 
in  1912,  58,098  in  1913,  60,874  in  1914,  80,020  in  1915,  67,699  in  1916,  and  75,764  in  1919. 

(B)  VASELINE  (or  mineral  fat).  This  was  prepared  for  the  first  time  by 
Cheeseborough  in  1871  and  forms  a  white,  buttery  mass  constituted  almost 
exclusively  of  various  high,  saturated  hydrocarbons. 

It  is  prepared,  especially  in  America,  by  heating  certain  pale,  crude,  Penn- 
sylvanian  petroleums  by  direct  fire  in  open  boilers,  and  passing  into  the 
mass  a  current  of  hot  air  until  the  desired  consistency  or  sp.  gr.  (0'86  to 
0'87)  is  reached.  The  mass  is  then  decolorised  by  passing  it,  while  still  hot, 
repeatedly  through  animal  charcoal  or  other  decolorising  agents  (see  p.  89). 
It  is  also  prepared  from  the  residues  of  Galician  and  German  petroleum  by 
diluting  them  with  benzine  and  repeatedly  refining  with  concentrated  sulphuric 
acid.  It  melts  at  33°  to  40°. 

Artificial  vaselines  are  also  placed  on  the  market,  these  being  obtained  by  dissolving 
paraffin  wax  or  cerasin  (see  later)  in  paraffin  oil ;  they  may  be  distinguished  from  the  natural 
vaselines,  the  latter  being  sticky  and  ropy  and  the  former  not.  At  60°  the  viscosity 
(Engler)  of  the  natural  vaselines  is  4-5  to  7-5,  and  that  of  the  artificial  ones  little  more  than 
1 ;  the  latter  contain  11  to  35  per  cent,  and  the  natural  vaselines  63  to  80  per  cent,  of 
paraffin  wax,  insoluble  in  98  per  cent,  alcohol  at  0°.  The  natural  vaseline  after  solution 
in  ether  and  precipitation  with  alcohol  forms  a  sticky  mass  and  the,  liquid  remains  turbid ; 
the  artificial  variety,  on  the  other  hand,  is  precipitated  in  flocks  and  the  liquid  is  left  clear. 

Gelatinised  vaseline  oil,  also  prepared  nowadays,  is  transparent  and  does  not  deposit 
paraffin  wax,  even  if  added  in  considerable  quantity;  it  is  obtained  by  heating  vaseline 

follows :  5  grams  of  the  oil  arc  heated  with  25  grams  of  60  per  cent,  alcohol  to  40°  to  50°  on  a 
water-bath,  the  mixture  being  well  shaken  until  it  emulsifies,  allowed  to  cool  and  filtered.  The 
alcohol  is  driven  off  from  the  nitrate  on  a  water-bath  and  the  cold  residue  treated,  drop  by  drop, 
with  2  tp  3  c.c.  of  dimethyl  sulphate  :  if  resin  oil  is  present,  a  red  coloration  is  produced. 


94  ORGANIC    CHEMISTRY 

oil  (sometimes  with  a  little  sulphuric  acid)  at  about  200°  and  adding,  at  a  certain  moment, 
a  small  quantity  of  soap. 

For  the  decolorisation  of  vaseline  and  vaseline  oil  see  above. 

Vaseline  is  used  in  pharmacy  for  the  preparation  of  unguent  medicines, 
also  for  the  preparation  of  lubricants,  and,  in  large  quantities,  for  coating 
metallic  articles  to  preserve  them  from  rusting  and  oxidation  ;  it  is  also  used 
in  the  manufacture  of  smokeless  powder. 

Italy  imported  the  following  amounts  of  vaseline  : 

w 


1908  1910  1912  1913  1914  1915  1916  1917  1918 

/Tons         34-8  21-7  42-3  45-2       33        99  106-9  327-6  189-5 

\Value,  £  2088  2538  1848  6842  26520 

fTons         75-7  88-1  81-6  64-2  51-2  16-6  181-1  43-4  151-7 


r 
Artificial  vaseline     Value>£2483 

In  1910  Germany  produced  5292  tons  of  vaseline  of  the  value  £36,000. 
France  imported  173  tons  in  1913,  73  in  1914,  935  in  1915,  and  828  in  1916, 
and  exported  107  tons  in  1913  and  156  in  1916. 

(C)  PARAFFIN  WAX.  This  was  first  found  in  petroleum  by  Fuchs  in 
1809,  and  Reichenbach  obtained  it  from  wood-tar  in  1830,  and  showed  its 
great  importance  as  an  illuminant. 

Hard  paraffin  wax  melts  at  54°  to  60°,  has  sp.  gr.  0'898  to  0'915,  and  forms 
a  white,  translucent  mass  used  for  the  manufacture  of  paraffin  candles  ;  it  is 
soluble  in  ether  (1'95  per  cent.),  petroleum  benzine  (11  '7  per  cent.),  carbon 
disulphide  (13  per  cent.),  turpentine  (6  per  cent.),  toluene  (3'9  per  cent.), 
chloroform  (2*4  per  cent.)  or  benzene  (2  per  cent.),  and  to  slight  extents  in  alcohol 
(0'22  per  cent.),  acetic  acid  (0*06  per  cent.),  acetone  (0'26  per  cent.),  or  acetic 
anhydride  (0*025  per  cent.).  By  fractional  distillation  of  paraffin  wax  in  a 
vacuum  Mabery  (1912)  isolated  tricosane  (see  Table,  p.  32),  tetracosane, 
pentacosane,  hexacosane,  octocosane,  and  nonocosane  (m.-pt.  62°  to  63°). 

Soft  paraffin  wax  with  m.-pt.  42°  to  48°  and  sp.  gr.  0'88  to  0'89  is  used  as 
an  adjunct  in  wax  and  stearine  candles,  to  impregnate  wooden  matches,  in 
dressing  textiles,  and  as  a  preventive  of  frothing  during  the  concentration 
of  saccharine  juices  (see  Sugar)  ;  it  serves  also  as  an  insulator  of  electrical 
conductors  and  as  a  cold  bath  in  the  manufacture  of  hardened  glass. 

Most  of  the  paraffin  wax  and  paraffin  wax  oil  is  obtained  from  ozokerite 
(see  later),  the  tar  distilled  from  the  bituminous  lignites  of  Saxony  and  Thuringia 
(pyropissite)  and  from  the  bituminous  shales  of  Scotland  and  Australia,  and 
also  from  boghead  coal  and  from  the  residues  of  American  and  Austrian 
petroleum.1 

I.  PARAFFIN  WAX  FROM  PETROLEUM  RESIDUES.  For  this  purpose  an 
apparatus  consisting  of  three  vertical  concentric  cylinders  is  used  ;  in  the  inner  and  outer 
ones  circulates  a  non-solidifying  brine,  which  has  a  temperature  of  —  20°  and  serves  to 
separate  the  paraffin  wax  from  the  mineral  oil  in  the  middle  cylinder  (see  also  p.  78). 
According  to  Tanne  and  Oberlander,Ger.Pats.  226,136  and  227,334,  paraffin  wax  is  obtained 
from  petroleum  and  tar  residues  by  dissolving  them  in  hot  benzine  and  glacial  acetic  acid  ; 
on  cooling,  the  solutions  deposit  paraffin  wax,  cerasin,  or  ozokerite;  see  also  Process  of 
Miss  Az).  To  free  the  flakes  of  paraffin  wax  from  the  adhering  oil  the  cold  mass  is  pressed 
in  filter-presses  (up  to  15  atmos.  )  and  the  cakes  thus  formed  are  finally  squeezed  in  hydraulic 
presses,  as  is  done  in  the  case  of  stearine  (see  this);  the  blocks  of  wax  are  then  spread  out 
in  a  warm  chamber,  where  the  last  traces  of  coloured  oils  flow  away.  In  the  Weiser  process 
the  hydraulic  presses  are  replaced  advantageously  by  filtering  tubes  wound  round  with- 

1  There  is  also  at  Messel,  near  Darmstadt,  a  special  layer  of  very  soft  and  moist  bituminous 
coal,  consisting  of  clay  and  lignite,  its  bitumen,  like  that  of  the  shales,  being  insoluble  in  the 
ordinary  solvents.  This  coal  contains  45  per  cent,  of  water  and  30  per  cent,  of  ash,  and  on 
distillation  yields  6  to  7  per  cent,  of  tar  and  6  per  cent,  of  gas  (see  p.  103  ). 


PARAFFIN    WAX  95 

linen;  the  paraffin  wax  from  the  filter-press  is  broken  up  and  forced  into  these  tubes, 
being  afterwards  removed  by  steam  and  sent  to  the  sweating  chamber.  The  sweated  oils 
are  refined  to  prepare  lubricating  mineral  oils  (see  p.  76). 

The  sweated  paraffin  wax  is  refined  by  means  of  sulphuric  acid  and  decolorising  agents, 
in  the  same  way  as  cerasin  is  refined.  If  the  petroleum  oils  are  distilled  in  a  vacuum, 
mineral  oils  are  obtained  which  give  a  greater  yield  of  paraffin  wax.  According  to  Tanne 
and  Oberlander  (Ger.  Pat.  238,489,  1911),  treatment  of  mineral  oil  residues  or  lignite  tars 
with  10  to  20  per  cent,  of  carbon  tetrachloride  readily  gives  paraffin  wax  or  cerasin  in 
good  yields. 

II.  PARAFFIN  WAX  FROM  LIGNITE  TAR  AND  FROM  PYROPISSITE.  This 
special  lignite,  pyropissite,  now  almost  exhausted,  is  obtained  from  deposits  of  oily  and 
resinous  woods  which,  according  to  Potonie  and  Heinhold,  underwent  fossilisation  during 
the  tertiary  epoch.  It  is  extracted  moist  (up  to  55  per  cent,  of  water)  from  the  mines  in 
Saxony  and  Thuringia,  especially  in  the  neighbourhopd  of  Halle  a/S.,  where  the  deposits 
are  35  to  40  metres  below  the  surface  and  have  a  thickness  of  2  to  5  metres  over  an  area 
of  about  a  square  kilometre.  It  forms  a  blackish-brown,  more  or  less  plastic  mass,  greasy 
to  the  touch,  and  when  dry  is  yellowish- brown,  friable  and  easy  to  burn;  its  sp.  gr.  is 
0-9  to  1-1.  In  the  dry  state  it  gives  up  to  alcohol  20  per  cent,  of  its  weight  of  a  substance, 
m.-pt.  75°  to  86°,  giving  paraffin  oil  on  distillation.1  The  rational  industrial  distillation 
of  these  more  or  less  fatty  lignites  or  of  the  corresponding  bitumens  was  commenced  in 
Saxony  and  Thuringia  after  1858  by  C.  A.  Eiebeck  (after  unsuccessful  attempts  to  carry 
out  the  distillation  in  the  usual  way,  no  matter  what  the  type  of  the  lignite)  and  improved 
later  by  Wernecke. 

The  distillation  of  the  broken  lignite  is  carried  out  in  large  vertical  refractory  (chamotte) 
retorts,  8  metres  high  and  2  metres  wide,  placed  in  a  suitable  furnace  so  that  the  external 
walls  are  heated  by  rational  circulation  of  the  hot  gases.  Inside  the  retort  are  arranged 
conical,  cast-iron  rings  superposed  one  on  the  other  with  a  certain  distance  between,  their 
diameter  being  12  to  20  cm.  less  than  that  of  the  retort  (see  Figure  of  a  similar  apparatus 
used  for  the  distillation  of  sawdust :  chapter  on  Acetic  Acid).  The  lignite,2  with  not 

1  E.  Erdmann  gives  the  following  results  of  analysis  and  distillation,  referred  to  100  parts 
of  dry  matter  (the  moisture  is  33  to  35  per  cent. )  : 

OH  OS  (volatile)          Ash          Tar       Coke       Gas 

Pyropissite         .         .     7M2         11-63  9-43  O'lO  7-72        65        20         15 

Bituminous  lignite      .     64-83          7'62         19-18  0'48  7'89        38        42        20 

The  sulphur  content  of  bituminous  lignites  never  exceeds  2  per  cent. 

The  distillation  products  of  these  lignites  consist,  to  the  extent  of  40  to  50  per  cent.,  of  slightly 
alkaline  water  (2°  to  3°  Be.  with  0-03  to  0-07  per  cent.  NH3)  from  which  it  does  not  pay  to 
recover  the  ammonia,  and  which  are  used  only  for  the  direct  irrigation  of  the  soil  adjacent  to  the 
works ;  they  sometimes  form  a  troublesome  waste  product,  which  must  be  treated  and  filtered 
before  running  into  rivers,  or  they  may  be  poured  on  to  the  ash-heap. 

One  ton  of  bituminous  lignite  yields  130  to  140  cu.  metres  of  gas  containing  :  10  to  20  per 
cent,  of  C02,  0-13  per  cent,  of  0,  1  to  2  per  cent,  of  heavy  hydrocarbons,  5  to  15  per  cent,  of 
CO,  10  to  25  per  cent,  of  CH4,  10  to  30  per  cent,  of  H,  10  to  30  per  cent,  of  N,  and  1  to  3  per 
cent,  of  H2S.  The  gas  has  a  calorific  value  of  more  than  3000  cals.  per  cubic  metre  and,  after 
removal  of  the  H2S,  serves  for  use  in  gas-engines,  1  to  1'5  cu.  metres  being  consumed  per  H.P.- 
hour  (one  retort  deals  with  about  3  tons  of  the  lignite  in  twenty-four  hours,  producing  about 
400  cu.  metres  of  gas).  The  gas  is  freed  from  ammonia  by  washing  with  water. 

After  quenching,  the  coke  remaining  from  the  distillation  contains  about  20  per  cent,  of  water 
and  volatile  products,  20  per  cent,  of  ash,  and  60  per  cent,  of  carbon.  When  dry,  its  calorific 
value  is  about  6000  cals.  and,  with  many  works,  the  profits  are  made  by  the  sale  of  the  coke. 

2  Now  that  the  deposits  of  pyropissite  are  almost  exhausted  and  the  paraffin  wax  industry 
of  Saxony  and  Thuringia  has  been  subjected  to  the  competition,  first,  of  ozokerite  (after  1870), 
and  then  (after  1880)  to  the  more  serious  one  of  the  American  paraffin  wax  extracted  from  Ohio 
petroleums — which  has  invaded  all  the  markets  of  the  world- — it  has  been  recently  discovered 
that  when  pyropissite  is  distilled  a  great  part  of  the  paraffin  wax  is  destroyed,  much  better 
yields  being  obtained  by  extracting  direct  with  suitable  solvents   (benzine,  toluene,  alcohol, 
carbon  disulphide,  carbon  tetrachloride,  acetone,  etc.),  which,  after  evaporation,  leave  a  waxy 
mass ;    when  this  is  purified  with  fuming  sulphuric  acid,  it  yields  an  almost  white  product  of 
great   value — montan  wax   (Bergwachs),  similar  to  cerasin    (mineral  wax).     The  remedy  for 
the  paraffin  wax  crisis  of  Saxony  and  Thuringia  has  arrived  too  late,  since  the  valuable  wax 
has  been  squandered  by  distillation.     Other  layers  of  lignite  from  the  region  of  Halle  a/S.  are 
being  worked  to-day,  and  these  are  extracted  in  the  hot  with  benzine;   the  solution  of  bitumen 
extracted  is  first  purified  by  thorough  cooling,  the  paraffins  being  thus  separated  while  the  resins 


96  ORGANIC    CHEMISTRY 

less  than  30  per  cent,  and  not  more  than  60  per  cent,  of  water,  is  charged  in  lumps  at  the 
top  and  descends  gradually  in  the  free  annular  space  between  the  walls  of  the  retort  and 
the  edges  of  the  rings.  When  it  reaches  the  bottom  it  consists  of  nothing  but  coke,  which 
is  discharged  occasionally,  fresh  lignite  being  introduced  at  the  top;  the  gaseous  pro- 
ducts are  evolved  at  140°  to  150°  by  a  large  tube  at  the  top,  and  the  liquid  products  (tar) 
flow  down  the  walls  of  the  rings  and  are  collected  by  a  lower  tube.  The  retorts  are 
maintained  at  a  dull  red  heat. 

From  a  cone  at  the  bottom  the  coke  is  discharged  every  hour  at  a  temperature  of  400° 
and  is  quenched  with  water.  The  vapours  emitted  are  drawn  off  and  gradually  condensed 
in  apparatus  consisting  of  superposed  iron  tubes  with  a  cooling  surface  of  80  to  100  square 
metres  enclosed  in  a  casing.  The  gases  which  do  not  condense  are  led  under  the  hearth 
to  heat  the  furnace,  fuel  being  thus  saved ;  formerly  5  to  6  tons  of  inferior  coal  were  used 
per  10  tons  of  lignite  distilled,  but  later  only  1  to  1-2  tons  were  necessary,  less  labour  being 
required  (one  workman  per  twenty  furnaces)  and  the  yield  per  furnace  being  increased  (by 
more  than  25  per  cent. ).  The  gases  passing  from  the  hearth  round  the  furnace  and  retorts 
have  a  temperature  of  500°  to  700°. x  Batteries  of  10  to  12  retorts  for  each  condensation 
unit  are  employed.  In  each  furnace  3-5  to  4  tons  of  lignite  in  pieces  the  size  of  walnuts 
are  distilled  in  twenty-four  hours.  The  lignites  now  distilled  give  only  4  to  8  per  cent,  of  tar. 

Lignite  tar  is  brownish  yellow  to  black  in  colour,  has  a  peculiar  odour,  and  liquefies 
between  25°  and  30°,  giving  a  greenish  fluorescence.  Its  specific  gravity  is  0-850  to  0-910 
at  44°.  It  has  an  alkaline  reaction  (from  ammonia,  ethylamine,  etc. )  and  contains  about 
20  to  25  per  cent,  of  paraffin  wax  2 ;  it  distils  between  80°  and  400°,  the  bulk  between  250° 
and  350°,  and  has  an  unpleasant  odour,  sometimes  of  hydrogen  sulphide.  The  best 
lignites  give  the  less  dense  tars.  According  to  the  nature  of  the  tar  (which  is  previously 
washed  with  acid  and  water  3)  the  paraffin  wax  is  obtained  from  it  in  the  following  ways 
(see  also  Part  III,  Distillation  of  Tar) : 

(these  are  recovered  by  evaporation  of  the  solvent;  they  melt  at  50°  to  60°  and  form  15  to  25 
per  cent,  of  the  crude  bitumen)  remain  in  solution.  The  bitumen  separated  in  the  cold  is  redis- 
solved  in  benzine  and  treated  with  concentrated  sulphuric  acid,  the  mass  being  kept  mixed 
and  slowly  heated  to  boiling.  Animal  charcoal  is  added  and  the  liquid  filtered,  passed  over 
fuller's  earth  (see  p.  89),  and  neutralised  by  passing  in  a  little  gaseous  ammonia.  After  distil- 
lation of  the  solvent  there  remains  a  yellowish  or  almost  white  paraffin  wax  melting  at  82°  to 
85°  (Ger.  Pat.  216,281,  1907). 

1  For  every  quality  of  lignite  and  every  type  of  furnace  preliminary  trials  should  be  made 
to  ascertain  the  most  suitable  temperature  for  obtaining  the  proper  decomposition  of  the  bitumen 
so  as  to  form  a  tar  poor  in  benzene  and  its  homologues,  naphthalene,  etc.  (produced  by  an  exces- 
sively high  temperature,  although  absence  of  these  substances  indicates  too  low  a  distillation 
temperature,  the  high  condensed  products  of  the  methane  series  then  containing  unaltered 
bitumen  and  the  gases  some  proportion  of  ethylene  and  acetylene;  when  the  temperature  is 
too  high,  the  gases  contain  hydrogen  and  light  hydrocarbons ).  Distillation  in  steam  affords  no 
advantage,  since  much  unchanged  bitumen  then  occurs  with  the  tar  and  no  ammoniacal  liquor 
is  then  obtained;  such  liquor  is,  however,  formed  in  abundance  when  Scotch  shales  are 
steam  -distilled . 

•  2  In  these  lignite  tars  and  bitumens  Kramer  and  Spiller  (1902)  found  an  ester  and  the  corre- 
sponding monobasic  acid,  but  no  glycerides  or  poly  basic  acids.  Hiibner  (1908)  found  two 
ketones,  C16H320  and  C^E^O,  and  a  humic  acid  containing  8-39  per  cent,  of  sulphur,  although 
other  investigators  found  only  5  per  cent,  and  1-7  per  cent,  of  sulphur. 

3  The  purification  of  lignite  tars  and  their  distillation  products  is  effected  by  means  of  acid 
and  alkali.  In  the  first  treatment  with  acid,  use  is  made  of  0-25  to  0-5  per  cent,  of  sulphuric 
acid  of  50°  Be.,  which  removes  traces  of  water  and  part  of  the  basic  products  (pyridine).  The 
second  treatment  with  3  to  5  per  cent,  of  sulphuric  acid  of  66°  Be.  (in  two  portions)  serves  for 
the  removal  of  all  the  residual  basic  products  and  part  of  the  unsaturated  hydrocarbons,  which 
otherwise  would  undergo  oxidation  and  resinification,  and  would  impart  a  dark  colour  to  the  oils ; 
the  sulphuric  acid  also  causes  slight  oxidation  (rendered  evident  by  the  marked  odour  of  S02) 
as  well  as  polymerisation  and  substitution.  The  action  of  the  acid  takes  place  in  the  cold, 
except  with  the  tar  itself  and  with  the  crude  paraffin  wax,  which  require  heat.  The  pitch  and 
resin  formed  on  treatment  with  sulphuric  acid  are  insoluble  and  are  deposited  on  the  walls  of 
the  vessel.  After  a  rest  of  three  hours,  the  acid  is  separated  by  decantation  and  the  residue 
washed  twice  with  water  (perhaps  with  a  little  added  calcium  hydroxide)  to  eliminate  the  last 
traces  of  acid,  and  then  treated  with  4  to  6  per  cent,  of  pure  caustic  soda  solution  (38°  to  40°  Be. ). 
Treatment  with  alkali  is  applied,  not  to  the  tar  itself,  but  only  to  its  distillation  products,  a 
small  amount  of  the  alkali  (or  recovered  alkali  solution)  being  first  used  and  then  the  bulk  of 
the  alkali ;  the  so-called  creosotes  (which  consist  of  phenol  and  its  homologues  and  impart  a  bad 
colour  and  smell  to  the  oil)  are  thus  removed- — -after  a  stand  of  three  hours.  The  alkali  treat- 
ment should  not  precede  that  with  acid,  since  there  are  products  soluble  in  both  alkali  and  acid 
and  it  is  more  economical  to  eliminate  the  bulk  of  these  by  means  of  sulphuric  acid  and  those 


WAX     FROM     LIGNITE     TAR  97 

( 1)  To  the  lignite  bitumen  or  tar  to  be  distilled,  0-2  to  0-5  per  cent,  of  slaked  lime  or 
of  solid  caustic  soda  is  added  to  fix  the  hydrogen  sulphide  and  part  of  the  creosote.  The 
distillation  is  continued  until  only  a  solid  residue  of  coke  remains.  With  2-5  tons  of  tar 
the  distillation  occupies  about  ten  hours,  about  0-6  ton  of  small  coal  and  0-05  ton  of  lignite 
being  consumed.  One  workman  suffices  to  control  the  distillation  in  ten  stills  and  another 
to  supervise  the  condensation  plant.  It  is  possible  also  to  distil  in  a  vacuum,  the  degree 
of  evacuation  being  low  at  the  beginning.  Sometimes  distillation  at  ordinary  pressure  in 
a  slow  current  of  steam  (maybe  superheated)  is  preferred.  Use  is  nowadays  made  of 
Wernecke's  continuous  apparatus  (see  Part  III :  chapter  on  Tar).  When  the  price  of 
paraffin  oils  is  too  low,  light  illuminating  oils,  etc.  (see  note,  pp.  75,  76  :  Benzine  from 
Naphtha)  may  be  obtained  by  distilling  them  under  pressure. 

With  very  dense  tars,  in  order  to  separate  the  creosote  and  certain  resinous  substances 
more  efficiently,  vacuum  distillation  in  large  direct-fired  boilers  is  resorted  to.  This 
yields  25  to  50  per  cent,  of  fatty  oils,  50  to  65  per  cent,  of  crude  paraffin  wax,  and  7  to  9 
per  cent,  of  coke,  which  is  burnt,  together  with  the  gases  from  the  distillation,  to  heat  the 
boilers.  The  mass  of  crude  paraffin  wax  is  purified  with  acid  and  alkali,  or  with  acid  and 
subsequent  distillation.  The  more  solid  part  is  then  separated  from  the  oily  part  by 
cooling  the  mass  in  vessels  holding  100  to  200  kilos,  around  which  circulates  a  very  cold 
solution  (the  non-solidifying  liquids  used  for  ice-machines,  see  Vol.  I.,  pp.  261,  621 ).  When 
the  oily  or  buttery  part  (which  is  distilled  for  the  extraction  of  solar  oil  and  second-grade 
paraffin)  is  separated  by  filtration  from  the  crystallised  paraffin  wax,  the  cakes  of  the 
latter  are  pressed  in  hydraulic  presses  at  150  atmos.  to  remove  the  20  per  cent,  of  oil  still 
contained  in  them.  The  solid  cakes  which  remain  are  yellowish  in  colour,  and  are  purified 
by  melting  them  several  times  with  10  to  15  per  cent,  of  benzine  and  pressing  them  at  200 
atmos.  in  a  hydraulic  press.  To  get  rid  of  the  smell  of  benzine  the  paraffin  wax  is  heated 
in  iron  cylinders  with  high-pressure  steam,  the  hot  wax  being  then  passed  through  the 
decolorising  material  [animal  charcoal,  ferro  cyanide  residues,  or  magnesium  hydrosilicate 
clay  (see  p.  89)].  The  small  quantity  of  this  material  retained  by  the  paraffin  wax  is 
finally  removed  by  filtration  through  paper,  the  wax  being  then  allowed  to  solidify  in  large 
shallow  moulds. 

Miss  Az  has  recently  suggested  the  purification  of  crude  paraffin  wax  by  treating  it 
either  fused  or  as  powder,  between  60°  and  70°,  with  a  solvent  (methyl  or  ethyl  alcohol, 
acetone,  or  acetic  acid  or  anhydride).  The  paraffin  wax  is  insoluble  and  the  impurities 
soluble  in  these  solvents.  Paraffin  wax  thus  purified  appears  to  be  of  better  quality  than 
that  purified  in  the  ordinary  way  (see  above  :  Weiser's  process). 

The  tar  is  sometimes  distilled  above  a  certain  temperature  with  superheated  steam; 

remaining,  which  are  less  soluble  and  more  easily  removable,  by  means  of  soda;    with  this 
procedure  less  secondary  decomposition  occurs. 

The  acid  treatment  is  carried  out  in  cylindrical  wrought-iron  tanks  with  conical  bases  lined 
with  pure  lead  4  mm.  thick,  the  mass  being  stirred  for  about  half -an-hour  by  a  stream  of  air. 

Tars  free  from  bitumen  are  best  treated  with  0-25  per  cent,  of  sulphuric  acid  of  50°  Be., 
then  with  3  to  4  per  cent,  of  acid  of  66°  Be.,  and  finally  with  hot  water  containing  a  little  milk 
of  lime,  formation  of  emulsions  being  avoided  by  thorough  agitation.  Distillation  of  the  tar 
then  gives  paler  products,  a  higher  yield  of  paraffin  wax  and  less  loss  of  gas,  etc.  If  the  tar 
contains  bitumen,  or  if  vacuum  distillation  is  employed,  such  preliminary  treatment  with 
sulphuric  acid  is  inadvisable. 

The  blue  fluorescence  shown  by  some  of  these  distillation  oils  is  removed  by  shaking  them 
with  0-25  to  0-5  per  cent,  of  nitronaphthalene,  which  separates  on  standing  and  is  then 
decanted  off. 

The  waste  Hack  acids  may  be  used  for  making  fertilisers  (superphosphates,  etc),  while  the 
•  acid  resins  and  pitches  may  bo  redistilled  to  the  extent  of  two-thirds,  the  remaining  one-third 
serving  as  tar  (goudron )  or,  if  denser,  as  asphalte.  Sometimes,  however,  these  resins  and  pitches 
are  mixed  with  alkali  creosotes,  the  water  (which  contains  sodium  sulphate)  being  removed  and 
the  resin  distilled,  while  in  some  cases  they  are  pulverised  by  means  of  steam  and  burnt  under 
the  boilers  (calorific  power,  8000  cals. ).  The  alkali  creosote  may  also  be  used  for  impregnating 
pit-props,  or  crude  creosote  may  be  liberated  by  treatment  with  dilute  sulphuric  acid  or  carbon 
dioxide  (flue  gases).  Acid  pitch  may  be  obtained  by  diluting  the  black  acid  mass  with  water, 
since  it  is  not  soluble  in  dilute  acid.  The  pitchy  and  resinov-s  masses  which  separate  may  be 
distilled  again,  various  products  (see  later)  being  obtained. 

Fairly  pure  concentrated  sulphuric  acid  may  be  recovered  (according  to  U.S.  Pat.  956,276, 
1910)  from  the  black  acid  by  allowing  it  to  fall  in  a  thin  stream  into  a  retort  containing  pure 
sulphuric  acid  heated  to  boiling,  the  acid  distilling  off  being  condensed  in  the  usual  way  (see 
Vol.  I.,  p.  308).  This  acid  may  also  be  decomposed  in  the  hot  to  obtain  SO2  (U.S.  Pat. 
956,184,  1910). 

VOL.  II.  7 


98 


ORGANIC    CHEMISTRY 


in  other  cases  only  the  benzines  (photogens)  and  the  light  oils  are  distilled,  the  residue  being 
cooled  to  a  low  temperature  and  the  solid  paraffin  wax  which  separates  centrifugated  to 
eliminate  the  tar  and  heavy  oils.  When  the  tars  are  very  dense  (above  0-900)  Krey  finds 
it  convenient  to  distil  them  under  a  pressure  of  about  10  atmos.,  thus  raising  the  tempera- 
ture to  400°  to  450°.  This  yields  60  per  cent,  of  distilled  oil  of  sp.  gr.  0-830,  which  is  largely 
used  for  the  preparation  of  oil-gas  (see  p.  64),  10  per  cent,  of  gas,  and  30  per  cent,  of  residual 
oily  tar. 

(2)  With  light  and  very  pure  tars  a  greater  yield  of  paraffin  wax  is  obtained  more 
cheaply  by  treating  the  tar  directly  with  concentrated  sulphuric  acid,  washing  with  water, 
and  subjecting  to  fractional  distillation  over  calcium  hydroxide.  Crystallisation,  pressing, 
and  bleaching  are  carried  out  as  described  above. 

The  following  scheme  shows  the  different  operations,  and  the  final  yields  in  a  tar 
distillation  (the  brackets  unite  products  which  are  worked  up  together,  generally  by 
distillation;  the  ultimate  products  are  shown  in  italics) : 

Tar 
(sp.  gr.  0- 830-0- 890) 


33  %  Crude  oil 


63  %  Crude  paraffin  wax 


Crude  solar  oil      Bed  oil      Pasty  mass  I  Expressed  oil      10  %  paraffin  wax  I 


• 

(m.-pt.  5l°-60°) 

lass  II 

Crude  s( 

)lar  oil         Re< 

I  oil        Pasty  n 

1 

1 

12%(sp.g 

r.  0-860-0-880) 

2  %  photogens 

(sp.  gr. 
0-800-0  810) 


10  %  solar  oil 

(sp.  gr. 
0-825-0-830) 


10  %  yellow  oil 

(sp.  gr. 
0-850-860) 


solar  oil 
residues 


3  %  fatty  oil 

(sp.  gr. 
0-880-0-890) 


1  %  pasty  distillate 
(m.-pt.  30-38°) 


20  %  dark'  paraffin  oil 

(sp.  gr. 
0-890-0-920) 


4  %  soft  paraffin  wax 
(m.-pt.  42°-48°) 


Photogen  is  a  species  of  benzine  similar  to  that  of  petroleum,  but  obtained  by  the 
distillation  of  wood,  lignite,  and  coal ;  it  is  used  in  the  purification  of  paraffin  wax,  in  the 
carburetting  of  lighting  gas,  and  for  removing  spots  from  fabrics.  Yellow  oil  is  used  for 
the  extraction  of  fats  and  for  cleaning;  red  oil  (sp.  gr.  0-860  to  0-880)  has  various  uses, 
and  serves  well  for  the  manufacture  of  oil-gas  (see  p.  64);  the  fatty  oils  and  dark  paraffin 
oils  (0'880  to  0-925)  are  used  as  oil  for  gas  l  and  for  making  cart-grease  ;  the  yellow  and  red 
oils  (0-880  to  0-900)  are  used  as  thinner  lubricants. 

1  Oils  for  Gas.  From  the  time  when  gasworks  began  to  mix  gas  obtained  by  the  carbonisa- 
tion of  bituminous  coal  with  carburetted  water-gas  and  with  oil-gas  (in  1905  Germany  produced 
30  000,000  cu.  metres,  England  500,000,000  cu.  metres,  and  the  United  States  1,550,000,000 
cu'.  metres  of  carburetted  water-gas),  the  use  of  mineral  oils  for  carburetting  the  water-gas  and 
for  producing  oil-gas  has  increased  considerably.  These  oils  for  gasifying  are  obtained  partly 
by  the  distillation  of  lignite  and  shale  tars  (see  above  and  p.  102),  but  more  especially  by  the 
distillation  of  petroleum  residues  (solar  oil,  intermediate  to  true  petroleum  and  lubricating  oils). 
The  value  of  these  oils  increases  with  the  narrowness  of  the  temperature  limits  within  which 
they  boil ;  these  limits  are  usually  100°  apart,  and  it  is  of  no  consequence  whether  they  be  200° 
and  300°, 'or  250°  and  350° ;  they  should  contain  less  than  25  per  cent,  of  unsaturated  hydrocarbons 
(soluble  in  concentrated  sulphuric  acid  of  sp.  gr.  1-83),  otherwise  they  give  too  much  tar  and  coke 
on  gasification ;  they  should  contain  not  more  than  30  per  cent,  of  creosote,  but  a  high  propor- 
tion of  paraffin  wax  is  advantageous.  In  the  United  States  600,000  tons  were  consumed  in  1908; 


ASPHALT  E,     PITCH    AND     BITUMEN          99 

The  washing  of  tar  and  of  its  distillates  with  alkalies  and  acids  yields  resinous  masses  with 
varying  proportions  of  creosote  oil  and  distillation  of  these  at  different  temperatures  yields 
goudron  or  asphalte  tar,  or  artificial  bitumen,1  which  is  used  in  the  manufacture  of  impermeable 

about  220,000  tons  were  imported  into  England  in  1906,  320,000  in  1909,  and  260,000  in  1910; 
about  4153  tons  of  mineral  oil  (sp.  gr.  0-83  to  0-88)  were  imported  into  Germany  in  1906,  29,600 
in  1908,  and  46,500  in  1910  for  the  carburetting  of  water-gas;  Germany  itself  produces  a  further 
quantity  of  about  300,000  tons  of  oil  for  gasifying,  13,000  tons  being  used  for  producing  oil-gas 
on  the  railways,  and  9000  tons  for  mineral-oil  engines.  For  the  carburetting  of  gas  these  oils 
should  cost  less  than  £4  16s.  per  ton.  The  amount  of  cart-grease  imported  into  Italy  is  about 
300  tons  per  annum,  and  that  exported  about  120  tons  (£800). 

1  Asphalte,  Pitch,  and  Bitumen.  When  tar  from  the  distillation  of  wood  (or  lignite)  is  heated 
until  all  the  volatile  products  are  eliminated,  there  remains  a  black  mass  which,  when  cold, 
assumes  a  glassy  consistency  and  forms  pitch,  used  particularly  for  caulking  ships,  for  preparing 
shoemakers'  thread,  and  for  making  cements  impermeable  to  water,  etc. 

When  coal-tar  is  completely  distilled  it  leaves  a  more  or  less  hard  black  residue — coal-pitch — 
which  is  used  for  ordinary  asphalting  and  for  making  varnishes,  lacs,  and  coal  briquettes  (see 
Vol.  I.,  p.  459).  Pitch  is  also  prepared  expressly  by  prolonged  heating  of  tar  in  a  current  of  air 
or  with  sulphuric  acid. 

Bitumen  (mineral  pitch)  bears  sometimes  the  unsuitable  name,  natural  asphalte,  and  forms 
a  brittle,  blackish  brown  mass,  which,  on  heating,  softens  between  100°  and  135° ;  it  has  the  sp.  gr. 
1-10  to  1-20  and  the  hardness  2.  It  burns  readily,  with  a  very  smoky  flame,  is  insoluble  in  water, 
alkali  or  acid,  slightly  soluble  in  alcohol  or  ether,  and  readily  soluble  in  benzene,  carbon  disulphide, 
and  turpentine  (in  which  it  ceases  to  be  soluble  after  exposure  to  light,  and  is  hence  used  in 
photo-lithography).  The  best  bitumen  is  found  at  the  surface  of  the  Dead  Sea  in  Palestine,  and 
in  greater  quantities  at  the  Pitch  Lake  in  the  island  of  Trinidad,  this  having  an  area  of  50  to  60 
hectares  (120  to  150  acres)  and  a  depth  of '50  metres,  and  forming  a  fairly  hard  mass ;  it  abounds 
also  in  Syria,  Utah,  Venezuela,  and  Cuba,  and  at  Dax  (France).  That  of  Trinidad  contains 
40  to  50  per  cent,  of  pure  bitumen  and  30  per  cent,  of  mineral  substances,  the  remainder  con- 
sisting of  organic  substances  and  water  (about  25  per  cent.).  It  is  broken  up  on  the  spot  by  means 
of  hatchets  into  brownish-black  lumps  permeated  with  bubbles  and  is  heaped  up,  the  interstices 
then  gradually  filling.  The  rights  of  working  belong  to  the  New  Trinidad  Lake  Company,  which 
pays  5s.  per  ton  to  the  British  Government.  By  means  of  a  telferage  line  1  kilometre  in  length, 
it  is  carried  to  the  port,  where  it  is  roughly  refined  by  melting  at  160°  to  170°  in  open  vessels 
heated  with  steam  coils  to  separate  part  of  the  mineral  substances,  water  and  volatile  matter, 
the  product  thus  obtained  containing  56  to  58  per  cent,  of  pure  bitumen,  having  the  sp.  gr. 
1-40  to  1-43  and  softening  at  85°  to  95°;  the  portion  soluble  in  petroleum  ether  bears  the  name 
petrolene,  and  consists  of  liquid  hydrocarbons  of  the  C»H2n_4  series,  whilst  the  insoluble  part 
is  known  as  aspJialte  and  is  composed  of  solid  substances,  which  are  partly  oxygenated  and 
undergo  oxidation  in  the  air.  Up  to  the  present  time  this  lake,  which  is  partly  covered  with 
vegetation,  has  yielded  over  a  million  tons  of  asphalte  and  its  level  has  been  lowered  about 
1-25  metres;  nowadays  about  250,000  tons  of  bitumen  are  extracted  from  it  per  annum. 

The  amount  of  change,  or  efflorescence,  which  bitumen  will  undergo  under  the  action  of 
air  and  light  may  be  estimated  by  determining  the  proportions  of  carbenes  present,  i.  e.,  the 
products  insoluble  in  carbon  tetrachloride,  but  soluble  in  carbon  disulphide. 

Pure  bitumen  is  used  for  making  black  sealing-wax,  black  lacs,  and  varnishes,  and  also  lamp- 
black; the  lower  qualities  serve  for  coating  wooden  structures  (boats,  telegraph  poles),  for 
cardboard,  for  roofs,  and  damp  walls,  etc.  (see  later). 

In  order  to  distinguish  natural  from  artificial  bitumen,  about  1  gram  of  the  substance  is  heated 
to  200°,  cooled,  powdered,  and  treated  with  5  c.c.  of  80  per  cent,  alcohol;  if  the  latter  turns 
yellow  and  exhibits  fluorescence,  artificial  bitumen  is  indicated,  whilst  if  the  alcohol  remains 
almost  colourless,  the  bitumen  is  natural. 

By  the  term  asphalte  (natural)  is  meant  minerals,  porous  rocks,  and  earth  containing  bitumen. 
Bituminous  rocks  are  slightly  porous  and  the  bitumen  they  contain  ( 10  to  15  per  cent.)  easily 
flows  away  when  they  are  heated  in  suitable  furnaces.  Asphaltic  rocks,  however,  are  porous 
limestone  impregnated  with  bitumen  (6  to  12  per  cent.,  or  even  over  20  per  cent.),  which  does 
not  flow  away  on  heating  :  they  are  used  for  the  preparation  of  asphalte  mastic  by  powdering 
and  fusing  them  homogeneously  with  a  certain  quantity  of  bitumen.  This  mastic  is  cooled 
in  moulds  and  is  used  directly  for  paving  streets  and  terraces,  either  alone  or  mixed  with  fine 
sand  or  gravel.  Powdered  asphalte  may  also  be  used  for  paving,  by  spreading  it  out  hot  and 
compressing  it  with  heavy  cast-iron  double  rollers  heated  inside. 

In  California,  large  quantities  of  artificial  asphalte  are  prepared  by  prolonged  injection  of  air 
into  dark  mineral  oils  (sp.  gr.  0-9333  to  0-9859)  heated  at  650°.  Fusion  of  colophony  at  250° 
and  addition  of  sulphur  yields  an  asphalte  which  is  similar  to  that  of  Syria  and  is  used  in 
photography. 

Natural  asphalte  occurs  abundantly  near  Neuchatel,  in  the  Department  of  Ain  (France), 
in  the  neighbourhood  of  Hanover,  and  in  Italy  at  Lettomonapello  (the  product  of  this  locality 
is  worked  at  S.  Valentino,  near  Chieti ),  and  especially  at  Ragusa  and  Castelluccio,  near  Modica 
(in  the  Sicilian  province  of  Syracuse).  These  Sicilian  asphalte  rocks  consist  of  pure,  more  or 
less  hard  chalk,  impregnated  with  7  to  14  per  cent,  of  bitumen,  and  until  1858  were  used  solely, 
and  to-day  are  used  partly,  for  the  manufacture  of  building  stone.  Almost  the  whole  of  this 
rock  is  exported,  the  exportation  amounting  to  1782  tons  in  1878,  2186  in  1882,  26,587  (£26,587) 
in  1894,  12,140  in  1897,  47,440  in  1899,  55,307  in  1903,  72,746  in  1905,  89,808  (£88,012)  in  1908, 


100 


ORGANIC    CHEMISTRY 


pasteboard  for  roofing,  in  rendering  woodwork  and  masonry  (especially  in  damp  houses) 
damp-proof,  and  also  in  the  manufacture  of  ultramarine. 

III.  Another  important  source  of  paraffin  wax  is  furnished  by  the  Bituminous  Schists, 
which  are  especially  abundant  in  the  Lothians  in  Scotland  (at  Broxburn,  Bathgate,  etc. ), 
where  at  depths  of  600  to  1200  metres  layers  2  to  4  metres  in  thickness  are  found  over  an 
area  95  kilometres  long  and  8  to  13  kilometres  wide. 

In  1848  Young  and  Meldrum  began  to  work  and  purify  a  special  oil  issuing  from  the 
surface  of  the  soil  in  Derbyshire  (see  note,  p.  66),  and,  having  exhausted  this  deposit  and 
not  finding  others,  they  succeeded  in  preparing  mineral  oils,  which  had  been  already  intro- 
duced for  illuminating  purposes,  by  distilling  cannel  coal,  which  gave  much  lower  but 
remunerative  yields. 

In  about  1860  they  discovered  that  the  interesting  Scotch  deposits  of  boghead  coal 
gave  a  yield  of  oil  much  greater  than  cannel  coal,  and  in  1864  and  1866  were  erected  the 
two  works  at  Bathgate  and  Addiwell,  which  became  world  famous.  The  deposits  of 
boghead  coal  were  exhausted  in  four  or  five  years,  and  were  then  replaced  by  the  more 
abundant,  although  less  fertile,  deposits  of  bituminous  schists  (shales)  in  which  Scotland  is 
so  rich.  These  shales  have  been  formed  by  the  slow  deposition  of  fish  at  the  bottom  of 

and  85,947  (47,759  to  Hamburg,  10,125  to  London,  4040  to  Buenos  Aires,  3800  to  Antwerp, 
3000  to  New  York,  2800  to  Rouen,  2720  to  New  Orleans,  2605  to  Rotterdam,  2537  to  Greece, 
2014  to  Alexandria,  1707  to  Hungary,  1050  to  Calcutta,  etc.)  in  1909.  The  mean  price  of  the 
rock  at  the  port  is  £1  per  ton.  These  Sicilian  deposits  were  studied  by  Delia  Fonte  and  Moschini 
in  1884,  Ragusa  in  1901,  Manzella  in  1906,  Maderna  in  1906  and  1909,  and  Coppadoro  and  Schiavo- 
Leni  in  1908-1910.  For  street  paving  these  powdered  rocks  should  contain  less  than  2  per  cent, 
of  residue  insoluble  in  hydrochloric  acid  (clay  and  silica)  and  should  be  free  from  pyrites  (in 
the  air  this  is  converted  into  soluble  ferrous  sulphate,  which  results  in  disintegration  of  the  pave- 
ment); the  proportion  of  bitumen  (extracted  by  chloroform  from  the  well-powdered  material, 
dried  at  100°,  in  a  Soxhlet  apparatus)  should  be  more  than  8  per  cent,  and  less  than  13  per  cent. 
Various  firms  export  asphalte  ready  powdered  from  Sicily  and  manufacture  asphalte  mastic 
(see  above)  by  mixing,  in  the  hot,  powdered  asphaltic  rock  with  either  Trinidad  bitumen  or 
bitumen  obtained  by  distilling  the  richer  rocks  (12  to  25  per  cent,  of  bitumen). 

By  the  name  asphaltite  are  known  certain  bitumens  found  naturally  in  veins  and  among 
these  Marcusson  (1914)  includes  Syrian  asphalte  or  bitumen,  Gilsonite,  Grahamite,  and  Albertite. 
These  are  more  expensive  than  other  bitumens,  and,  being  harder  and  more  shiny  and  more 
easily  powdered,  are  used  more  especially  in  the  lac  industry.  They  are  distinguished  chemic- 
ally from  asphaltes  and  bitumens  by  their  content  of  organic  acids,  organic  sulphur  and  matter 
soluble  in  CS2  and  CC14.  As  they  contain  less  than  7  per  cent,  of  oils  resistant  to  sulphuric  acid, 
they  are  to  be  regarded  as  products  of  more  advanced  decomposition  than  bitumen. 

STATISTICS  AND  PRICES.  The  Italian  output  of  asphaltes  and  bitumens  is  as 
follows  (tons) : 


1910 

1912 

1933 

1914 

1915 

1916 

1917 

Natural  asphalte  rock    . 

162,212 

181,397 

171,097 

119,853 

47,650 

16,829 



Powdered  asphalte  rock 

26,137 

34,648 

40,573 

17,200 

11,279 

5,607 

— 

Asphalte  in  cakes  (bituminous 

mastic)      .... 

13,953 

16,612 

13,961 

13,772 

11,460 

8,477 

— 

Artificial  asphalte 

8,580 

6,200 

6,000 

4,700 

— 

— 

—  • 

Compressed  asphalte  bricks    . 

943 

1,164 

1,790 

2,249 

2,187 

1,618 

— 

Crude  bitumen 

457 

549 

393 

326 

355 

786 

.  —  • 

Refined  bitumen 

672 

283 

426 

531 

775 

960 

— 

Solid  bitumen,  importation.    . 

3,365 

3,548 

4,300 

2,924 

4,139 

1,090 

1,381 

,,          ,,         exportation     . 

26,125 

13,158 

6,596 

6,367 

6,720 

121 

111 

The  production  of  pitch  in  Italy  was  7220  tons  in  1909,  11,964  (£25,920)  in  1912,  17,746  in 
1915,  and  30,182  (£122,668)  in  1916. 

Great  Britain  imported  68,389  tons  of  asphalte  and  bitumen  in  1909  and  69,398  tons 
(£168,000),  together  with  12,000  tons  of  pitch  (excluding  that  from  coal  tar),  valued  at  £66,000 
(the  exports  being  of  the  value  £720,000 ),  in  1910.  The  output  of  oily  shales  was  2,967,700  tons 
in  1909,  3,130,000  (£430,000)  in  1910,  3,280,143  in  1913,  and  3,268,666  (£837,240)  in  1914. 

In  Germany  there  were  fifteen  works  treating  asphalte  rocks  (costing  about  8s.  6d.  per  ton ) 
in  1910,  the  quantity  treated  being  76,964  tons  (giving  4400  tons  of  asphalte)  in  1909,  and  81,335 
tons  (giving  4640  tons  of  asphalte)  in  1910.  The  imports  were  130,062  tons  in  1908  and  98,370 
(exports  14,200  tons)  in  1909;  103,000  tons  were  produced  in  1905,  89,000  (£40,000)  in  1908, 
and  77,500  in  1909. 

The  prices  are  :  for  the  tar  (goudron),  £3  5s.  per  ton;  Archangel  pitch,  I,  £11  4s.;  Swedish 
pitch,  £9 -4s.;  coal  pitch,  £2  to  £2  8s.;  lignite  pitch,  £2  8s.  to  £3  4s.;  stcarine  pitch,  £7  4s.  to 
£14  8s.;  Syrian  asphalte,  I,  £34;  asphalte  in  fine  powder,  £70. 


SHALE:    CU  -I:'-   '<:< 


101 


the  sea,  with  interposition  of  deposits  of  clay,  which  even  now  bears  the  imprints  of  the 
fish.  They  are  greyish-black  or  brownish,  with  a  lamellar  structure,  and  have  the  sp.  gr. 
1-71  to  1-87.1 

The  invasion  of  American  petroleum  in  about  1880  created  a  serious  crisis  in  this 
industry,  which  was  partially  saved  by  new  and  improved  technical  methods  introduced 
by  engineers  and  chemists,  especially  by 
Beilby,  Henderson,  Crichton,  and  Bryson ;  the 
by-products  were  more  completely  utilised, 
the  furnaces  improved,  fractional  distillation 
apparatus  brought  into  use,  the  ammoniacal 
liquors  utilised,  the  tar,  coke,  gas,  and  final 
residues  employed  as  fuel,  and  the  labour 
reduced  to  a  minimum ;  the  mineral  oil  came 
to  occupy  a  secondary  position,  attention 
being  paid  to  the  production  of  paraffin  wax 
and  high-class  lubricating  oils  for  engines. 

The  furnaces  and  retorts  used  in  Scot- 
land for  the  distillation  of  bituminous  shale 
have  undergone  continuous  improvement. 
Horizontal  retorts  gave  way  to  vertical  ones, 
and  of  these  the  most  perfect  types  are  the 
Henderson  retorts,  brought  into  use  in  about 
1895  at  Broxburn,  and  the  Bryson  retorts, 
applied  later  at  Pumpherston,  both  being 
modifications  of  the  old  vertical  retorts  of 
Young  and  Beilby  (called  also  Pentland 
retorts).  The  furnace  with  Bryson  retorts  is 
shown  in  Fig.  103.  The  retorts  are  9  metres 
high,  have  a  circular  section  with  a  mean 
diameter  of  90  cm.,  and  hold  4-5  cu.  metres 
of  shale  in  lumps  of  walnut  size  (the  old 
Henderson  retorts  contained  3  and  the  old 
Pentland  retorts  1  cu.  metre).  The  lower 

.  l  In  France  these  bituminous  schists,  which 
abound  in  the  basin  of  the  Autun  and  at  Buxiere- 
les-Mines,  form  two  strata  which  are  1  to  2  metres 
thick  and  extend  over  an  area  of  18,000  hectares 
(44,460  acres ),  the  best  deposits  being  at  a  depth 
of  80  metres.  They  were  first  worked  in  1837 
by  Selligne  in  consequence  of  the  studies  of 
Reichenbach  (1830),  and  the  industry  became  a 
nourishing  one  about  1860 ;  in  1864, 128,550  tons 
of  shale  were  distilled,  producing  4750  tons  of 
crude  oil,  destined  principally  to  prepare  oil-gas 
in  the  large  towns.  The  invasion  of  American 
petroleums  also  overthrew  this  industry,  which 
now  survives  on  account  partly  of  the  Customs 
duty  and  partly  of  the  adoption  of  Scotch  distil- 
lation furnaces  (Fig.  103),  which  give  improved 
yields. 

In  Australia,  especially  in  the  neighbourhood 
of  Sydney,  extensive  deposits  (from  a  few 
centimetres  to  2  metres  thick)  of  bituminous 
shale  occur  which,  according  to  Potonie,  origin- 
ated in  oily  algae,  and  are  hence  to  be  regarded 
as  coals  rather  than  as  shale.  On  distillation 
they  give  68  per  cent,  of  oils,  14  per  cent,  of  gas, 
11  per  cent,  of  crude  paraffin  wax,  and  7  per 
cent,  of  ash. 

A  bituminous  schist  from  Midlothian  (Scotland)  gave  on  analysis  :  20  per  cent,  carbon, 
0-7  per  cent,  nitrogen,  1-5  per  cent,  sulphur,  the  rest  being  mineral  matter;  it  gave  up  nothing 
soluble  to  ether.  Another  sample  showed  2-7  per  cent,  water,  24-3  per  cent,  tar,  and  73  per  cent, 
residue  (ash).  Certain  French  shales  give  only  5  to  6  per  cent,  of  tar,  whilst  those  from 
Australia  give  as  much  as  60  per  cent.,  but  are  poor  in  paraffin  wax.  Unlike  that  of  bituminous 
lignites,  the  tar  of  shale  cannot  be  extracted  by  solvents. 


FIG.  103. 


102  0  R  G  A  -K1" C    CHEMISTRY 

two-thirds,  6,  of  the  retorts  is  of  refractory  bricks  (chamotte)  and  the  upper  part,  a, 
of  cast-iron  fixed  with  mastic  into  the  chamotte  part.  The  shape  is  slightly  conical, 
and  at  the  upper  end  is  a  large  sheet-iron  hopper,  c,  containing  sufficient  broken 
shale  to  feed  the  retort  for  twenty-four  hours.  The  mouth  at  the  bottom  of  the 
retort  is  restricted  somewhat  and  is  closed  with  a  hinged  grid  or  disc,  which  is  divided 
into  two  parts  and  may  be  opened  by  the  lever  arms,  k,  so  as  to  discharge,  every 
five  to  six  hours  or  more  frequently,  part  of  the  exhausted  shale  into  the  sheet-iron  hopper, 
d,  where  it  cools  to  some  extent ;  at  the  same  time  fresh  material  enters  the  retort  at  the 
top.  The  retorts  with  their  hoppers  below  are  united  in  pairs,  a  single  discharge  orifice,  s, 
serving  the  two.  In  each  retort  5  tons  of  shale  are  distilled  per  twenty -four  hours.  The 
furnaces  are  heated  by  the  non- condensable  gases  from  the  distillation,  these  being  intro- 
duced through  the  pipes  A  and  B.  The  distilled  products  are  evolved  at  the  top  through 
the  tubes  e  and  are  aspirated  through  the  tubes  /  to  the  condensing  plant.  This  consists 
of  batteries  of  vertical  wrought-  or  cast-iron  tubes,  wh'ich  are  60  cm.  in  diameter  at  the 
beginning  and  45  cm.  at  the  end  of  the  battery  and  rest  on  adjacent  but  separate  tanks, 
in  which  the  various  products  collect  as  they  are  gradually  condensed  by  the  cold  external 
air-  (cooling  with  water  with  the  object  of  diminishing  the  number  of  tubes  has  not  given 
good  results;  in  some  cases,  batteries  of  small  air-cooled  tubes  are  used).  Batteries  of 
forty  to  sixty  furnaces  are  controlled  by  four  workmen  by  day  and  two  by  night  (the 
hoppers,  c,  are  charged  during  the  daytime).  The  gases  heating  the  retorts  have  a  tempera- 
ture of  about  700°  at  the  bottom  and  400°  at  the  top,  flow  of  the  bitumen  before  distilla- 
tion and  the  production  of  obstructions  being  thus  avoided.  In  some  instances  the  retorts 
are  also  heated  internally  by  means  of  superheated  steam.  With  regular  working  100  kilos 
of  shale  give  8  to  10  kilos  of  tar.  The  yield  is  about  6  per  cent,  of  gas,  8  per  cent,  of 
ammoniacal  liquor  (ammonium  carbonate),  12  per  cent,  of  crude  oil  (tar),  and  7  per  cent, 
of  residue  (4  to  5  per  cent,  of  which  consists  of  combustible  matter).  The  crude  oil  con- 
tains less  than  0-03  per  cent,  of  sulphur ;  the  gas  evolved  contains  21  to  23  per  cent.  C02, 
1  to  4  per  cent.  CO,  12  to  24  per  cent.  H,  1-6  per  cent,  of  heavy  hydrocarbons,  8  to  20 
per  cent.  CH4,  1-2  to  4  per  cent.  O  and  35  to  43  per  cent.  N.1 

The  crude  oil  is  dark  green,  has  the  sp.  gr.  0-865  to  0-895  at  44°,  and  is  semi-solid  at 
ordinary  temperatures  owing  to  the  paraffin  wax  present. 

This  oil  is  treated  by  virtually  the  same  methods  as  are  used  for  lignite  tar,  that  is, 
by  continuous  distillation  in  a  current  of  steam,  so  as  to  obtain  purer  products.  The  first 
distillation  gives  :  green  naphtha,  (0-753)  and  green  oil  (0-858),  which  are  purified  by  acid 
and  alkali  and  then  redistilled  :  the  first  gives  commercial  mineral  oil  (also  solar  oil)  and 
the  second  light  oils  and  paraffin  wax,  which  is  separated  by  cooling  from  the  blue  oil, 
which  serves  as  a  good  lubricant  when  refined.  The  paraffin  wax  is  purified  by  the  process 
given  above  (paraffin  wax  of  lignite  tar).  The  gas  evolved  during  the  distillation  of  crude 
shale  oil  showed,  in  one  instance,  the  following  percentage  composition :  heavy  hydro- 
carbons, 14-5 ;  methane,  59 ;  ethane,  26-5 ;  hydrogen,  traces ;  CO,  C02,  and  O,  nil.  When 
this  gas  is  cooled,  a  light  benzine  for  automobiles  is  obtained. 

1  One  hundred  kilos  of  Scotch  shale  gives  on  distillation  in  modern  furnaces  as  much  as 
30  cu.  metres  of  gas  (only  14  with  the  older  furnaces)  containing,  for  instance,  22-08  per  cent. 
CO2,  1-18  per  cent.  0,  1-38  per  cent,  heavy  hydrocarbons,  9-77  per  cent.  CO,  3-70  per  cent.  CH4, 
55-56  per  cent.  H,  and  6-33  per  cent.  N;  the  very  high  content  of  hydrogen  is  due  to  the  action 
of  the  water-vapour  on  the  red-hot  residues  of  the  shale. 

The  distillation  residues,  consisting  almost  entirely  of  mineral  matters,  have  no  value,  and 
are  used  for  filling  holes  in  the  ground ;  in  some  few  cases,  the  residues  (coke )  contain  as  much 
as  12  per  cent,  of  combustible  substances  and  are  then  mixed  with  better  fuel  and  burnt  in  the 
furnaces. 

In  1876,  when  horizontal  retorts  were  used,  the  cost  of  100  litres  of  tar,  including  the  value 
of  the  raw  shale,  was  estimated  at  8s. ;  in  1879,  with  Henderson  vertical  retorts,  at  4s.  Gd.,  and 
in  1897,  with  the  new  retorts,  at  3s.  6d. 

The  gases  used  for  heating  the  furnaces  consist  of  80  per  cent,  of  water-gas  and  20  per  cent, 
of  distillation -gas  and  tar  vapours  (2  per  cent. ).  In  some  modern  works  the  quantity  of  gas  is 
increased  by  passing  steam  in  at  the  bottom  of  the  furnace,  this,  with  the  carbon  remaining  in 
the  hot,  exhausted  shale,  giving  water-gas  rich  in  hydrogen  and  carbon  monoxide. 

The  waters  distilled  from  shale  form  three-fourths  by  weight  of  the  distillate  have  the  sp.  gr. 
4°  Be.,  and  contain  ammonia  and  pyridine.  The  ammonia  is  recovered  as  crystallised  sulphate 
by  the  method  used  in  gasworks.  Each  ton  of  shale  gives  5  to  6  kilos  of  ammonium  sulphate, 
which  in  many  factories  is  the  sole  source  of  profit.  Benzene  is  also  obtained  from  the  gas  by 
washing  the  latter  with  paraffin  oil  in  a  coke  tower  or  scrubber. 


ICHTHYOL  103 

A  ton  of  bituminous  schist  (of  the  value  of  12s.  Qd.)  yields  about  8  kilos  of  naphtha, 
115  kilos  of  crude  oil  (green  oil),  and  13  kilos  of  ammonium  sulphate.  From  100  kilos 
of  green  oil  are  then  obtained  31  kilos  of  burning  oil,  13  kilos  of  lighting  oil,  11  kilos  of 
middle  oil,  15  kilos  of  paraffin  wax,  and  15  to  20  per  cent,  of  gas,  water,  and  loss,  the 
remainder  being  coke  (about  3  per  cent. ),  which  is  used  as  a  black  pigment. 

In  1873,  524  tons  of  oily  shales  were  treated  in  Scotland,  in  1893  about  2,000,000 
tons,  and  in  1909  3,000,000  tons,  giving  280,000  tons  of  crude  oil.  The  Scotch  shale- 
oil  refineries  produced  in  1908  90,000  tons  of  burning  oil,  16,000  tons  of  engine  oil, 
40,000  tons  of  gas-oil,  40,000  tons  of  lubricating  oil,  25,000  tons  of  paraffin  wax,  and 
60,000  tons  of  ammonium  sulphate.  In  1908  134,163  tons  of  bituminous  shale,  of  the 
value  £72,400,  were  produced  in  Italy.  In  France  219,000  cubic  metres  were  distilled 
in  1890. 

In  Germany  80,000  tons  of  lignite  tar  (corresponding  with  600,000  tons  of  lignite)  are 
distilled  annually,  and  the  products  obtained  (9000  tons  of  paraffin  wax — two-thirds  hard 
and  one-third  soft — 5000  tons  of  solar  oil,  and  3500  tons  of  heavy  oil)  have  a  value  of 
about  £880,000.! 

Tar  can  be  purchased  from  the  lignite  distilleries  at  little  more  than  lOd!.  per  quintal 
(2  cwt. )  and,  treated  as  above,  yields  14s.  5d.  to  16s.,  taking  as  the  average  selling  prices 
per  quintal :  paraffin  wax,  £3  12s. ;  solar  oil,  10s.  5d. ;  yellow  oil  of  paraffin,  12s.  lOrf. ; 
dark  oil  of  paraffin,  10s.  5d. 

The  competition  of  the  Galician  product  lowered  the  price  of  paraffin  wax  in  1910 
and  1912  to  £20  per  ton.  In  various  countries  there  are  special  bituminous  shales  which 
have  originated  from  the  decomposition  of  immense  heaps  of  fish  accumulating  at  the 
bottom  of  former  seas,  the  decomposition  products  being  interlayered  with  clay  and  then 
carried  by  geological  convulsions  to  the  surface  of  the  earth  and  to  the  summits  of 
mountains.  These  shales  abound  in  the  residues  of  numerous  different  fish  and  also  in 
vegetable  d6bris,  and  the  bitumen  or  oil  obtained  from  them  by  distillation  contains  large 
proportions  of  organic  sulphur  (2  to  10  per  cent. )  and  nitrogen  (24  per  cent. ),  which  impart 
to  the  crude  oil  an  unpleasant  odour  and  a  deep  brownish-yellow  colour  with  greenish 
reflection. 

The  most  important  deposit  of  these  ichthyolic  shales,  which  are  worked  industrially 
for  the  preparation  of  ichthyol  2  (used  extensively  in  medicine,  especially  for  the  treatment 

1  The  bituminous  coal  of  Messel  (see  note,  p.  94)  is  utilised  in  a  special  way,  the  vapour 
derived  from  the  drying  of  the  coal  being  employed  in  the  upper  part  of  the  vertical  retort  to 
produce  water-gas.     The  vapour  is  injected  by  means  of  a  blower  into  the  bottom  of  the  retort, 
where  it  meets  red-hot  coke,  all  the  nitrogen  of  the  latter  being  transformed  into  ammonia, 
which  issues  with  the  water-gas  and  the  vapours  from  the  distillation  at  a  point  about  one-third 
up  the  retort,  (Ger.  Pat.  200,602,  1906).     This  process  for  utilising  the  nitrogen  of  the  coke  is 
derived  from  that  patented  by  A.  Grouven  in  1878  (hence  prior  to  the  Mond  process)  for  the 
utilisation  of  the  nitrogen  of  peat..    To  fix  the  ammonia  of  the  gases  and  vapours,  these  are 
passed  into  a  species  of  Glover  tower,  in  which  they  are  washed  by  a  spray  of  dilute  sulphuric 
acid,  the  ammonium  sulphate  solution  obtained  being  concentrated  to  crystallisation  by  means 
of  the  heat  of  the  furnace  and  of  the  distillation  products,  which  are  thus  appreciably  cooled. 
The  tar  from  the  Messel  coal  has  the  sp.  gr.  0-855  to  0-860  at  44°. 

2  Ichthyol  is  an  oil  of  sp.  gr.  0-865  which  is  obtained  between  100°  and  255°  during  the  dry 
distillation  of  ichthyolic  bituminous  shale.     On  distillation  it  yields,  besides  a  highly  luminous 
gas,  5  to  7  per  cent,  of  crude  ichthyol.     On  distillation,  these  shales  lose  30  to  40  per  cent,  of 
their  weight.     The  Besano  oil  is  richer  in  pyridine  bases  than  that  of  Seefeld,  which  contains 
1  per  cent,  of  them  (Baumann  and  Schotten,  Contardi  and  Malerba). 

Treatment  of  this  oil  (when  redistilled  it  is  almost  colourless  and  contains  2-5  per  cent,  or 
more  of  sulphur)  with  concentrated  sulphuric  acid  yields  ichthyolsulphonic  acid  containing  10 
to  15  per  cent.  S  (like  sulphoricinates )  and  forming  salts  (ichthyolsulphonates)  with  soda,  or  better 
with  ammonia,  which  are  used  in  the  cure  of  skin  diseases.  Ammonium  ichthyolsulphonate 
(C22H,606S3(NH4)2  ?),  which  commonly  bears  the  name  of  ichthyol,  forms  a  dense,  reddish  brown 
liquid,  soluble  in  water,  and  its  solution  gives  a  black  resinous  deposit  with  HC1  and  yields  NH3 
when  treated  with  KOH ;  it  dissolves  also  in  a  mixture  of  alcohol  and  ether. 

When  heated  in  the  air  it  burns  without  leaving  a  residue,  while  at  100°  it  does  not  lose  more 
than  50  per  cent,  of  its  weight  (water).  If  a  current  of  steam  is  passed  on  to  the  surface  of 
boiling  ichthyol,  the  latter  is  rendered  almost  odourless  (Knoll  &  Co.,  Ger.  Pat.  118,542,  1899), 
but  deodorisation  with  hydrogen  peroxide  destroys  the  medicinal  properties ;  the  deodorised 
product  is  termed  desichthyol. 

The  best  qualities  of  ichthyol  contain  between  3  to  5  per  cent,  and  8  per  cent,  of  sulphur 
as  sulphonic  group  and  between  4-5  per  cent,  and  14  per  cent,  of  sulphur  as  SH,  the  total  sulphur 
amounting  to  12  to  18  per  cent,  and  the  combined  ammonia  to  2-5  to  4-3  per  cent.  Aniline  is 
an  ammonium  ichthyolsulphonate  purified  by  means  of  alcohol;  its  aqueous  solution  dissolves 


104  ORGANIC    CHEMISTRY 

of  painful  sores  and  inflammations)  occur  at  Seefeld  and  at  Beith,  near  Innsbruck  in  the 
Tyrol ;  similar  deposits  are  found  in  various  parts  of  Italy. 

IV.  Another  source^  one  of  the  most  important,  of  paraffin  wax  is  Ozokerite 
(or  mineral  wax}.  It  is  found  in  England,  Russia,  and  America,  but  the 
deposits  of  greatest  industrial  and  historical  importance  are  those  of  Galicia 
(that  of  Boryslaw  gives  3000  tons  and  that  of  Dzwiniacz  about  1000  tons 
per  annum,  while  those  of  Pomiarki  and  Starunia  are  of  inferior  quality), 
where  it  occurs  in  seams  as  much  as  a  metre  in  thickness.  It  was  discovered 
by  Doms  when  searching  for  petroleum,  and  from  1860-1870  was  worked  by 
the  Landesberg  process  for  the  extraction  of  a  kind  of  paraffin  wax,  which 
competed  keenly  with  that  of  Saxony  and  Thuringia  (from  lignite,  see  p.  95) ; 
in  1870,  Pilz  and  Ujhelyi  found  that  simple  treatment  of  ozokerite  twice  with 
concentrated  sulphuric  acid,  followed  by  decolorisation  -  with  prussiate  black 
(see  Vol.  I.,  p.  840),  yields  cerasin,  a  product  of  greater  value  than,  and  similar 
to,  beeswax.1  In  the  State  of  Utah,  the  industrial  treatment  of  ozokerite  was 
begun  in  1888,  and  in  1890  already  yielded  as  much  as  600  tons  of  crude  cerasin. 

In  recent  years  the  decolorisation  of  ozokerite  has  been  simplified,  but  whereas  with 
paraffin  wax  fuller's  earth  (see  Vol.  I.,  p.  738;  also  this  Vol.,  chapter  on  Vegetable  Oils) 
may  be  used  as  a  decolorising  agent  in  place  of  prussiate  black  (which  is  increasing  in 
price  owing  to  diminished  production),  this  does  not  serve  in  the  case  of  cerasin.  A  special 
decolorising  material,  termed  francolite  or  tonsile,  gives,  however,  complete  decolorisation 
at  one-half  the  cost,  after  a  single  treatment  of  the  ozokerite  with  sulphuric  acid ;  extrac- 
tion of  the  decolorised  residues  with  benzine  is  then  somewhat  difficult,  but  the  difficulty 
is  overcome  by  using  trichloroethylene  (see  p.  122),  which  is  denser,  and  by  extracting  in 
lead-lined  apparatus. 

Ozokerite  forms  an  amorphous  mass  of  a  yellow,  brown,  greenish,  or  black 
colour  and  of  varying  consistency ;  the  harder  varieties  show  a  fibrous  fracture ; 
the  specific  gravity  is  0*85  to  0'95,  and  the  m.-pts.  of  the  various  commercial 
varieties  are  84°  to  86°,  65°  to  76°,  and  55°  to  65° ;  these  contain  less  than  5  per 
cent,  of  moisture  and  volatile  products.  Pure  ozokerite  contains  85  to  86  per 

many  substances  insoluble  in  water  (camphor,  volatile  oils,  phenol,  etc.).  The  ichthyolsul- 
phonates  of  the  heavy  metals  are  only  slightly  soluble  in  water. 

Of  the  many  other  derivatives  (and  substitutes,  e.  g.,  thyd,  obtained  by  treating  tar-oils 
with  sulphur),  mention  may  be  made  of  ichthyoform  (blackish  brown,  inodorous),  prepared  by 
treating  ichthyolsulphonic  acid  with  formaldehyde  and  used  as  an  antiseptic  for  the  intestines 
and  instead  of  iodoform  for  curing  wounds ;  it  costs  £4  per  kilo  and  ammonium  ichthyolsulphonate 
£1  per  kilo. 

1  The  material  from  the  mines  (shafts  80  metres  or  more  in  depth),  which  contains  admixed 
earth  and  stones,  is  placed  in  open  vessels  holding  300  litres  and  heated  by  direct  fire  heat ;  the 
mineral  matter  settles  to  the  bottom  and  is  separated  by  decantation.  This  matter  still  con- 
tains 10  per  cent,  of  wax,  which  is  extracted  with  benzine  (extraction  wax);  both  this  and  the 
decanted  part  (fusion  wax)  form  the  prime  materials  treated  in  the  refineries  found  in  all 
countries. 

The  refining  is  carried  out  in  large  iron  boilers  holding  up  to  3000  kilos  of  the  crude  wax,  half 
a  metre  being  left  free  to  take  the  scum  which  forms.  The  fused  mass  is  kept  at  115°  to  120° 
for  four  to  five  hours  and  is  stirred  to  liberate  all  the  water;  15  to  25  per  cent,  (according  to 
the  quality  of  the  wax)  of  fuming  sulpmiric  acid  containing  65  per  cent,  of  free  S03  is  then  added, 
in  a  thin  stream,  to  the  mass,  which  is  thoroughly  stirred  meanwhile;  the  temperature  rises 
slowly  to  165°  and  then  to  175°,  with  vigorous  evolution  of  S02  and  formation  of  froth,  which 
may  overflow  and  take  fire  if  the  hearth  is  not  well  isolated.  The  oxidisable  impurities  separate 
as  a  black  mass  (asphalte)  and  the  excess  of  sulphuric  acid  evaporates.  The  vessel  is  covered 
and  provided  with  a  draught-pipe  to  carry  off  the  acid  vapours.  When  emission  of  S02  ceases, 
the  mass  is  heated  to  180°  to  200°  and  then  allowed  to  cool  slowly,  being  neutralised  and  decolor- 
ised with  5  to  6  per  cent,  of  cyanide  Uack  [which  is  the  residue  from  the  old  method  of  making 
yellow  prussiate  (see  Vol.  I.,  p.  840)  and  contains  animal  black,  alkaline  earth  carbonates  and 
phosphates,  and  iron  oxide  and  sulphide]  or  with  blood  carbon,  and  is  sent  hot  to  the  filter- 
presses.  The  mass  obtained  is  still  slightly  yellow  and  is  whitened  by  further  treatment  with 
sulphuric  acid.  When  beeswax  is  to  be  imitated,  turmeric,  quinoline  yellow  or  other  coal-tar 
dye  is  added,  together  with  a  little  Peru  balsam  to  impart  the  required  odour.  The  filter-press 
residues  are  mixed  with  sawdust  or,  better,  with  rice  husks,  and  extracted  with  benzine  to  recover 
all  the  cerasin ;  after  recovery  of  the  benzine,  the  insoluble  residue  is  used  as  fuel. 


PARAFFIN     WAX     STATISTICS  105 

cent,  of  carbon  and  14  to  15  per  cent,  of  hydrogen,  and  hence  consists  principally 
of  paraffins,  together  with  a  small  proportion  of  defines ;  it  is  soluble  in  benzine, 
turpentine,  petroleum,  ether,  and  carbon  disulphide,  but  only  slightly  so  in 
alcohol.  It  forms  an  excellent  electrical  insulator,  and  may  be  used  in  place 
of  gutta-percha. 

According  to  Hofer,  ozokerite  has  been  formed  by  the  slow  evaporation, 
during  many  centuries,  of  petroleum  rich  in  paraffin  wax. 

On  distillation  it  yields  :  2  to  8  per  cent,  of  benzine,  15  to  20  per  cent,  of 
naphtha,  36  to  50  per  cent,  of  paraffin  wax,  15  to  20  per  cent,  of  heavy  oils, 
and  10  to  20  per  cent,  of  residual  solids. 

STATISTICS  AND  PRICE  OF  PARAFFIN  WAX.  The  importation  of  paraffin  wax, 
cerasin  and  vaseline  into  Italy  was  as  follows  (tons) : 

1905     1908     1910    1912     1913     1914    1915     1916     1917 

Paraffin  wax    .      8878      11932     19153    25584    24557     21042    32436    33638    26278 
Cerasin  .         .      41-7          111          88         110          76       89-3  40       18-5         3-2 

Vaseline  .  110-5     109-4        124      109-4         84         116        288        471 

In  1908  fourteen  factories  in  Germany  treated  70,000  tons  of  lignite  tar,  worth  about 
£160,000,  and  produced  45,000  tons  of  oil,  11,000  tons  of  crude  paraffin  wax  (equal  to 
7600  tons  of  the  pure  wax,  worth  £220,000),  and  8000  tons  of  creosote,  tar,  and  pitch,  of 
the  total  value  of  £450,000;  about  1,000,000  tons  of  lignite  were  distilled  and  350,000  tons 
of  coke  left.  For  several  years,  however,  the  industry  has  been  stationary.  In  1910 
Germany  imported  17,000  tons  of  paraffin  wax  and  wax  candles,  besides  46,500  tons  of  gas- 
oil.  In  order  to  offer  more  effective  resistance  to  the  crushing  competition  of  Austria 
(Galicia),  the  five  largest  German  works  combined  in  1913,  with  a  capital  of  more  than 
£3,200,000,  three  small  factories  remaining  outside  of  the  combine. 

France  imported  624  tons  of  ozokerite  in  1913,  483  in  1914,  and  335  in  1915. 

Galicia  produced  2116  tons  of  ozokerite  and  62,000  of  paraffin  wax  in  1910. 

The  United  States  exported  75,000  tons  of  paraffin  wax  in  1905,  90,000  in  1910,  and 
96,000  (£1,440,000)  in  1911 ;  95  per  cent,  of  the  American  output  is  in  the  hands  of  the 
Standard  Oil  Company. 

The  petroleum  of  Tscheleken  (Russia)  contains  up  to  8  per  cent,  of  paraffin  wax  and 
is  treated  in  a  Baku  works,  which  produced  34  tons  of  wax  in  1908,  160  in  1909,  600  in 
1910,  and  700  in  1911. 

In  1907  Great  Britain  produced  3500  tons  of  paraffin  wax,  and  in  1909  imported 
50,000  tons  (£1,400,000)  and  exported  17,000  tons  (£408,000);  in  1910,  14,000  tons  were 
exported.  The  Scotch  shales  yielded  23,000  tons  of  paraffin  wax  in  1910. 

Spain  imported  paraffin  wax  to  the  value  of  £90,400  in  1909-and  £112,000  in  1910. 

The  market  price  of  paraffin  wax  varies  somewhat  with  its  melting-point :  first  quality 
white,  m.-pt.  38°  to  40°,  costs  £39  per  ton;  that  with  m.-pt.  42° 'to  44°,  £41 ;  m.-pt.  48°  to 
50°,  £43;  m.-pt.  56°  to  58°,  £46;  m.-pt.  60°  to  62°,  £50.  That  used  in  pharmacy,  m.-pt. 
74°  to  76°,  costs  as  much  as  £96,  and  the  crude  wax  about  £29.  For  some  years  before  the 
war  the  price  was  lowered  considerably,  owing  to  the  large  output  in  Galicia,  whence  it  was 
exported  even  at  £16  per  ton. 

Pure  white  cerasin  resembles  wax,  melts  at  62°  to  80°,  has  the  sp.  gr.  0-918  to  0-922, 
and  is  dextro-rotatory.  It  is  used  in  making  candles,  in  perfumery,  as  dressing  for  textiles, 
in  making  boot-  and  floor-polish,  waxed  paper,  pomades  and  cosmetics,  crayons,  etc.  It 
is  subject  to'  much  adulteration  1  owing  to  its  high  price.  Before  the  war,  first  quality 
yellow  cerasin,  m.-pt.  62°  to  63°,  cost  £54  per  ton;  second  quality,  £46^  that  with  m.-pt. 
68°  to  70°,  £60,  and  the  white  variety,  m.-pt.  52°  to  63°,  £66.2 

1  The  analysis  of  paraffin  wax,  vaseline,  cerasin,  mineral  oils,  etc.,  is  described  in  treatises 
dealing  with    the   analysis   of   industrial   products,  e.  g.,  Villavecchia's  "  Applied  Analytical 
Chemistry,"  Vol.  I. 

2  A  mixture  of  cerasin  and  paraffin  wax  may  be  detected  by  the  following  tests  :  a  glass  rod 
3  mm.  in  diameter  is  immersed  to  a  depth  of  1  cm.  in  the  fused  substance,  extracted,  allowed  to 
cool,  and  hung  in  a  test-tube  heated  externally  with  water.     If  the  wax  drops  above  66°,  it  is 
pure  cerasin,  whereas  if  it  drops  below  66°  it  is  regarded  as  mixed  with  paraffin  wax  or  as  the 
latter  alone.     The  dropping -point  may  be  determined  also  with  the  Ubbelohde  apparatus  (p.  6). 
Addition  of  colophony  is  recognised  by  the  acid  number  or  saponification  number,  colophony 
being  saponifiable  and  cerasin  not. 


106 


Cerasin  has  been  made  in  continually  diminishing  quantity  since  1913,  owing  to  its 
cost,  and  even  in  making  candles  has  been  replaced  more  or  less  completely  by  paraffin 
wax.  The  high  price  of  cerasin  depends  on  that  of  ozokerite,  which  is  now  partially 
exhausted  and  occurs  to  some  extent  at  great  depths  (300  metres  at  Boryslaw  and  100 
metres  at  Dzwiniacz). 

The  ozokerite  worked  in  Austria-Hungary  in  1877  amounted  to  8961  tons;  in  1885, 
13,000  tons;  and  in  1894,  6742  tons.  The  exportation  of  cerasin  was  3594  tons  in  1891, 
and  2382  tons  in  1895. 

In  the  United  States  the  production  of  refined  ozokerite,  which  was  160  tons  in  1888, 
rose  in  1892  to  75,000  tons,  of  the  value  of  £4,000,000. 


(b)  UNSATURATED    HYDROCARBONS 
I.  ETHYLENE   SERIES  :   CnH2fl  (Alkylenes  or  defines) 

Two  groups  belong  to  this  series  :  the  olefine  group,  the  first  member  of 
which  is  ethylene,  C2H4,  the  succeeding  ones  being  open-chain  hydrocarbons 
with  a  double  linking  between  two  carbon  atoms,  since  hydrogen,  halogens, 
ozone,  etc.,  can  be  readily  added  to  them,  transforming  them  into  saturated 
compounds  of  the  paraffin  series. 

The  other  group  yields  additive  products  only  with  difficulty,  and  its 
members  are  formed  of  closed  carbon-chains  (cyclic  compounds}.  The  first 
term  is  trimethylene  or  cyclopropane,  hexamethylene  and  higher  compounds 
being  known  : 


H 


CH2 

/\ 

H2C  —  CH 

Trimethylene 


H2C< 


>CH2 


H 


Hexamethylene 


The  carbon  atoms  in  these  last  compounds  are  all  in  the  same  conditions 
and  cannot  be  differentiated.  The  cyclic  compounds  will  be  studied  as  a 
separate  section  of  the  aromatic  series  (Part  III). 

The  following  Table  gives  the  more  important  members  of  the  olefine  series 
(the  numbers  in  parentheses  representing  boiling-points  under  reduced  pressure) : 


Melting- 
point 

Boiling- 
point 

Melting- 
point 

Boiling- 
point 

Ethylene,  C2H4  . 

-  169° 

-  103° 

Decylene,  C10H20 

— 

172° 

Propylene,  C3H6 

— 

-48° 

Endecylene,  CnH22 

— 

195° 

Butylene  (3  isoms.  ),  |  ^ 
C  H                        1  " 

— 

-5°  ; 
+  1°  ' 

Dodecylene,  C^H^j     . 
Tridecylene,  C13H26 

-  31°        (96°) 
233° 

*8                                    (y 

— 

—  6° 

Tetradecylene,  C14H28. 

-  12° 

(127°) 

Amylene  (5  isoms.  ), 

Pentadecylene,  C15H30 

— 

247° 

c5Hi<>; 

Hexadecylene  (Cetene) 

\      40  (     274° 

Normal  amylene 

— 

+  35° 

C16H32 

/        :    \    (155°) 

Hexylene,  C6H12 

— 

68° 

Octadecylene,  C18H36  . 

+  18°      (179°) 

Heptylene,  C7H14 

— 

98° 

Eicosylene,  C20H40 

—            — 

Octylene,  C8H16 

— 

124°    1  Cerolene,  C27H54 

+  58° 

— 

Nonylene,  C9H18 

— 

153° 

Melene,  C30H6(1   . 

+  62° 

The  official  nomenclature  of  the  defines  is  the  same  as  that  of  the  paraffins, 
excepting  that  the  final  ane  is  changed  into  ene  (thus  ethylene,  which  is  isologous 
with  ethane,  is  called  ethene,  and  so  on;  see  also  p.  29). 

These  unsaturated  hydrocarbons  differ  little  in  their  physical  properties  from 
the  corresponding  saturated  homologues. 


ETHYLENE     HYDROCARBONS  107 

The  first  terms — up  to  C4H8 — are  gases,  and  after  C5H10  come  liquids  with 
increasing  boiling-points,  these  gradually  approaching  one  another  as  with 
the  paraffins;  the  higher  members  are  solid  and,  like  the  paraffins,  have  the 
sp.  gr.  0'63  to  0'79,  are  insoluble  in  water,  but  soluble  in  alcohol  or  ether. 

The  chemical  properties  differ  somewhat  from  those  of  the  saturated  com- 
pounds. Thus,  they  readily  take  up  HC1,  HBr,  HI,  Cl,  Br,  I,  fuming  H2S04, 
hypochlorous  acid  (giving  chloro-alcohols  or  chlorhydrins,  e.  g.,  CH2  :  CH2  -f 
HC10  =  CH2C1 '  CH2OH),  hyponitrous  acid,  ozone,  etc.,  forming  compounds 
of  the  saturated  series. 

Cl  is  added  more  easily  than  I  (see  Iodine  number  :  chapter  on  Fats),  Br 
occupying  an  intermediate  position,  whilst  HI  is  added  more  easily  than  HBr, 
and  this  more  easily  than  HCl.  With  these  acids,  the  halogen  is  added  to  the 
carbon  atom  with  which  the  least  hydrogen  is  combined. 

Ethylene  unites  with  fuming  sulphuric  acid  at  the  ordinary  temperature 
and  with  the  ordinary  acid  at  165°,  forming  ethylsulphuric  acid,  C2H50  •  S03H ; 
with  higher  compounds,  the  acid  radicle  passes  to  the  less  hydrogenated  carbon 
atom. 

They  often  polymerise  under  the  action  of  sulphuric  acid  or  zinc  chloride ; 
for  example,  amylene,  C5H10,  forms  C10H20,  and  C15H30  gives  C20H40. 

They  are  readily  oxidisable,  for  example,  with  potassium  permanganate 
or  chromic  acid  (not  with  nitric  acid  in  the  cold),  the  chain  being  then  broken 
at  the  double  linking,  with  formation  of  oxygenated  compounds  (acids)  con- 
taining fewer  carbon  atoms  in  the  molecule.  Careful  use  of  permanganate 
results  initially  in  the  addition  of  two  hydroxyl  groups  without  breaking  .the 
chain  and  forming  dihydric  alcohols  (glycols),  for  example,  OH  •  CH — CH  •  OH.1 

Almost  all  compounds  with  a  double  linking  between  atoms  of  carbon  give 
Baeyer's  reaction,  that  is,  they  rapidly  discharge  the  violet  colour  of  a  dilute 
solution  of  potassium  permanganate  and  sodium  carbonate,  with  formation  of 
a  reddish-brown  flocculent  precipitate  of  hydrated  manganese  peroxide. 

This  reaction  is  not  given  by  reducing  substances  like  aldehydes  or  by  certain 
aromatic  compounds  (phenanthrene,  etc.). 

With  tetranitromethane  they  give  a  yellow  or  brown  coloration  (the  nitro- 
derivatives  and  organic  acids  being  exceptions),  tautomeric  enolic  compounds 
also  reacting  in  this  way  (see  p.  18  :  I.  Ostromislenski). 

All  compounds  with  doubly  linked  carbon  atoms  give  the  ozone  reaction 
(Harries,  1905,  and  Molinari,  1907),  that  is,  when  dissolved  in  a  suitable  solvent 
they  fix,  quantitatively  and  in  the  cold,  the  ozone  contained  in  a  current  of 
ozonised  air  passed  through  the  solution;  in  this  property  they  differ  from 
compounds  with  either  a  triple  linking  or  a  benzene  double  linking  (E.  Molinari, 
Ann.  Soc.  Chim.  Milan,  1907,  116). 

Of  interest  also  are  the  formolite  and  nitric  acid  reactions  (see  pp.  71,  91). 

METHODS  OF  PREPARATION.  (1)  They  are  formed,  together  with 
petroleum,  in  the  dry  distillation  of  wood,  lignite,  coal,  paraffin  wax 
("cracking,"  see  pp.  87,  etc.). 

1  From  what  has  been  said  up  to  the  present,  it  is  obvious  that  a  double  linking  does  not  signify 
a  firmer  union  between  carbon  atoms ;  it  is  simply  a  conventional  sign.  The  breaking  of  the 
chain,  by  oxidising  agents,  at  the  double  linking  is  to  be  attributed  to  the  ease  of  formation  of 
intermediate  products  (e.  g.,  dihydric  alcohols)  rather  than  to  a  less  attraction  existing  between 
carbon  and  carbon  at  that  point.  Such  readiness  to  react  may,  according  to  Baeyer,  be  explained 
by  regarding  the  affinities  of  the  carbon  atom  as  orientated  or  grouped  at  four  poles  arranged 
like  the  vertices  of  a  regular  tetrahedron  (see  pp.  19  et  seq.).  If  two  carbon  atoms  unite  by  a 
double  linking,  the  poles  at  the  surface  of  the  carbon  atoms  become  displaced  and  approach  one 
another,  so  that  there  results  a  certain  tension  which  explains  the  readiness  with  which  the  double 
linking  reacts  or  opens.  After  the  initial  oxidation  leading  to  these  intermediate  products,  further 
action  of  the  oxidising  agent,  as  a  general  rule,  oxidises  or  breaks  the  chain  at  a  point  where  oxygen 
already  exists,  that  is,  where  the  oxidation  is  already  begun  (see  Part  III,  The  Hypothesis  of  the 
Partial  Valencies  of  the  Benzene  Nucleus). 


108  ORGANIC    CHEMISTRY 

(2)  By  eliminating  water  from  the  alcohols,  CnH2n  .  jOH,  by  heating  them 
with  dehydrating  agents   (H2S04,  P205,  ZnCl2,  etc.);    a  stable  intermediate 
product  is  sometimes  formed,  e.  g.,  ethylsulphuric  acid,  C2H5  •  HS04,  which  at 
a  higher  temperature  gives  ethylene  and  sulphuric  acid.     Higher  alcohols  and 
ethers  are  resolved,  merely  on  heating,  into  olefines  and  water. 

(3)  From     saturated     halogen     derivatives,     CnHn+1X     (X  =  halogen), 
especially  from  secondary  and  tertiary  bromo-  and  iodo-derivatives,  by  heating 
them  with  alcoholic  potash,  or  by  passing  their  vapours  over  heated  lime  or 
lead  oxide,  etc. 

C5HnI  +  C2H5OK  =  KI  +  C2H5  •  OH  +  C5H10. 

The  mixed  ether,  C5HU  •  O  '  C2H5,  may  also  be  formed  to  some  extent. 

(4)  From  dihalogenated  compounds  by  heating  with  zinc  : 

C2H4Br2  +  Zn  =  ZnBr2  +  C2H4. 

(5)  By  electrolysis  of  dibasic  acids  of  the  succinic  acid  series  : 

C2H4(COOH)2  =  C2H4  +  2C02  +  H2. 

(6)  Unsaturated  compounds  are  obtained  by  heating  the  condensation 
products  of  the  ketenes  (q.v.). 

CONSTITUTION  OF  THE  OLEFINES.  In  this  group  it  is  assumed  that  between 
two  carbon  atoms  there  exists  a  double  linking  :  H2C  =  CH2,  H2C  =  CH — CH3,  etc.,  the 
presence.of  two  free  valencies,  thus,  H2C — CH2  or  HC— CH3,  being  excluded  for  the  following 
reasons  |  |  A 

In  unsaturated  compounds  the  addition  of  halogen  does  not  take  place  at  a  single  carbon 
atom,  so  .that  ethylene  chloride,  C2H4C12,  has  not  the  formula  CH3  •  CHC12,  which  is  that 
of  ethylidene  chloride  obtained  from  acetaldehyde,  CH3  •  CHO,  by  replacement  of  the  O  by 
C12  (by  the  action  of  PC15).  Since  ethylene  chloride  is  chemically  and  physically  different 
from  ethylidene  chloride,  the  former  must  have  the  constitutional  formula,  CH2C1— CH2C1, 
and  the  third  formula  for  ethylene,  CH3 — CH<^  is  thus  excluded.  The  second  formula  is 
not  probable  because,  if  the  existence  of  free  valencies  is  assumed,  they  could  occur  also  in 
non-adjacent  carbon  atoms,  and  thus  give  rise,  in  the  higher  hydrocarbons,  to  numerous 
isomerides  which  have,  however,  never  been  prepared  (if  propylene  had  two  free  valencies, 
four  isomerides  should  exist,  instead  of  only  one);  further,  the  addition  of  halogen  always 
takes  place  at  two  contiguous  carbon  atoms  (see  Note  on  preceding  page). 

Finally,  the  assumption  of  free  valencies  in  organic  compounds  is  inadmissible  in  view 
of  the  unsuccessful  attempts  to  prepare  methylene  (or  methene),  CH2,  for  instance,  by  elimin- 
ating HC1  from  methyl  chloride,  2CH3C1  =  2HC1  -f  2CH2< ;  the  two  methylene  residues 
always  condense,  forming  ethylene,  as  the  two  valencies  cannot  remain  free. 

ETHYLENE,  C2H4  (Ethene),  H2C  =  CH2.  This  is  a  gas,  becoming  liquid 
at  —103°  and  solid  at  —169°,  or  liquid  at  0°  under  44  atmos.  pressure.  It 
is  very  slightly  soluble  in  water  or  alcohol.  It  has  a  somewhat  pleasant  smell 
and  burns  with  a  luminous  flame ;  indeed,  illuminating  gas,  which  contains 
2  to  3  per  cent,  of  ethylene,  owes  part  of  its  luminosity  to  this  gas.  When 
mixed  with  2  vols.  of  chlorine  it  burns  with  a  dark-red  flame,  carbon  being 
deposited  and  HC1  formed.  At  a  red  heat  it  yields  C,  CH4,  C2H6,  C2H2,  etc. ; 
with  hydrogen  in  presence  of  spongy  platinum  or,  better,  powdered  nickel  at 
300°,  it  is  converted  into  ethane. 

It  is  prepared  in  the  laboratory  by  heating  alcohol  with  excess  of  sulphuric 
acid;  as  an  intermediate  product,  ethylsulphuric  acid  is  formed,  this  giving 
ethyle-ne  when  heated  :  C2H5  •  OH  +  H2SO4  =  H2O  +  C2H5HS04 ;  C2H5HS04 
=  H2SO4  +  C2H4.  Pure  ethylene  is  obtained  (1)  by  passing  a  mixture  of 
carbon  monoxide  and  hydrogen  over  finely  divided  nickel  or  platinum  at  100°  : 
2CO  -J-  4H2  =  C2H4  -j-  2H20 ;  (2 )  by  dropping  alcohol  on  to  phosphoric  acid 
at  200°  to  220° ;  or  -(3)  from  ethylene  bromide  and  a  copper  zinc  couple. 


DIOLEFINES  109 

PROPYLENE,  C3H6  (Propene),  CH2  =  CH—  CH3.  This  may  be  prepared  by  heating 
glycerol  with  zinc  dust  or  from  isopropyl  iodide  and  potassium  hydroxide.  It  is  a  gas 
which  liquefies  at  —48°  and  is  isomeric  with  trimethylene. 

BUTYLENES,  C4H8  (Butenes).  Three  isomerides,  the  a,  ft,  and  y,  are  known,  and  are 
obtained  by  treating  normal,  secondary,  and  tertiary  butylene  iodides  respectively  with 
potassium  hydroxide  : 

CH2  -  CH  —  CH2  —  CH3        CH3  —  CH  -  CH  —  CH3          .      C 

C 

Butene-1  (a-butylene)  Butene-2  (/3-butylene)  2-Methylpropene  (isobutylene) 

Tetramethylene  or  cylobutane  is  isomeric  with  the  butylenes. 

AMYLENES,  C5H10  (Pentenes).  Of  the  various  isomerides  theoretically  possible 
several  have  been  prepared.  By  heating/^seZ  oil  (of  distilleries)  with  zinc  chloride,  pentanes 
and  various  isomeric  amylenes  are  formed  which  may  be  separated  by  means  of  the  different 
velocities  with  which  HI  is  added"  to  them,  or  by  the  property  possessed  by  some  of  them 
of  dissolving  in  the  cold  in  a  mixture  of  concentrated  sulphuric  acid  and  water  in  equal  parts, 
forming  amylsulphuric  acid,  whilst,  the  others  either  do  not  react  or  give  condensation 
products  (di-  and  triamylenes). 

NORMAL  OCTYLENE  or  CAPRYLENE,  C8H16,  is  formed  as  a  secondary  product  in 
the  preparation  of  octyl  iodide  (from  octyl  alcohol  and  phosphorus  iodide).  It  is  a 
colourless  liquid,  b.-pt.  124°,  and  with  concentrated  nitric  acid  forms  nitro-  and  dinitro- 
octylene. 

CEROTENE,  C27H54,  and  MELENE,  C30H60,  are  similar  to  paraffin  wax,  and  are 
obtained  by  distilling  Chinese  wax  or  beeswax. 

II.  HYDROCARBONS   OF   THE   SERIES,    CwH2n_2 
A.  With  Two  Double  Linkings  (Diolefines  or  Allenes) 

Of  the  few  known  terms  of  this  series,  the  first  and  best  investigated  is  ALLENE, 
H2C  :  C  :  CH2  (propandiene)  :  this  is  a  colourless  gas  which  differs  from  its  isomeride  allylene 
in  not  forming  metallic  derivatives;  it  is  obtained  by  eliminating  one  atom  of  bromine 
from  tribromopropane  by  means  of  potassium  hydroxide  and  the  remaining  two  by  zinc 
dust,  its  constitution  being  thus  rendered  evident  : 

CH2Br  •  CHBr  •  CH2Br->CH2  :  CBr  •  CH2BrCH2  :  C  :  CH2. 

ERYTHRENE,  C4H6  (Pyrrolilene  or  Butan-1  :  3-diene),  CH2  :  CH  •  CH  :  CH2,  is  a  gas 
found  in  illuminating  gas,  and  when  heated  with  formic  acid  gives  erythritol. 

ISOPRENE,  C5H8,  boils  at  37°  and  is  obtained  by  distilling  rubber.  On  the  other 
hand,  with  concentrated  HC1,  it  condenses,  regenerating  rubber  or  forming  terpenes,  C10H16, 

CTT 
CjgH^,   etc.     Since  dimethylallene,   pTT3]>C  •  C  :  CH2,  gives,    with   2HBr,   a   dibromide, 

CH  • 

r     3^>CBr  •  CH2  •  CH2  •  Br,  which  is  identical  with  that  obtained  from  isoprene  +  2HBr, 


v 

the  constitution  of  isoprene  must  be  -  \C  •  CH  :  CH2. 

CH/ 

Isoprene  was  prepared  for  the  manufacture  of  synthetic  rubber  by  decomposing  turpentine 
in  various  ways,  first  by  Tilden  in  1882,  and  later  by  Woltereck  (1909),  Wallace  (1909), 
Harries  (1910),  and  Silberrad  (1910  :  see  Eng.  Pats.  19,701  and  27,908  of  1909,  and  4001 
of  1910).  The  Badische  Anilin-und  Soda-Fabrik  (French  Pat.  425,885  and  Addition  No. 
14,542,  1911)  passes  vapours  of  turpentine  or,  better,  of  limonene,  dipentene,  carvone,  etc., 
over  metallic  filaments  rendered  red-hot  by  the  passage  of  an  electric  current,  the  product 
being  diluted  either  with  indifferent  gases  or  by  evacuation. 

Harries  (1910)  obtains  isoprene  by  heating  halogenated  derivatives  of  isopentane  at  600° 
in  presence  of  basic  oxides,  carbonates,  or  organic  salts.  According  to  U.S.  Pat.  1,206,419 
(1912)  isoprene  (or  diolefines  in  general)  is  obtained  on  passing  the  vapours  of  dihalogenated 
paraffins  [e.  g.,  trimethylethylene  bromide  (CH3)2  :  €Br  •  CHBr  •  CH3]  at  300°  into  a  vacuum 
over  heated  barium  chloride  (catalyst)  and  washing  the  resulting  vapours  in  water  to  fix 
the  HBr. 


110  ORGANIC    CHEMISTRY 

The  normal  isomeride,  PIPERYLE'NE,  CH2  :  CH  •  CH2-  CH  :  CH2  (Pentan-1  :  4-diene) 
boils  at  42°  and  is  obtained  from  piperidine. 

DIALLYL,  C6H10  (Hexine),  is  prepared  by  the  general  reaction — the  action  of  sodium 
on  allyl  iodide — which  indicates  its  constitution  : 

2CH2  :  CH  •  CH2I  +  2Na  =  CH2  :  CH  •  CH2  •  CH2  •  CH  :  CH2  +  2NaI. 

CONYLENE,  C8HU  (1  :  4-octadiene),  CH2  :  CH  •  CH2  •  CH  :  CH  •  CH2  •  CH2  •  CH3, 
'boils  at  126°,  and  is  obtained  from  coniine. 

B.  Hydrocarbons  with  Triple  Linkings  (Acetylene  Series) 

The  most  important  members  of  this  series  are  : 
Acetylene,  C2H2  (ethine),  HC  =  CH,  gas. 
Allylene,  C3H4  (propine),  CH3'C  =  CH,  gas. 

Crotonylene,  C4H6  (2-butine  or  dimethylacetylene),  CH3  •  C  '  C  •  CH3,  boils 
at  27°. 

Ethylacetylme,  C4H6  (3-butine),  CH3  •  CH2  •  C  :  CH,  boils  at  18°. 
Methylethylacetylene,  C5H8  (3-pentine),  CH3  •  CH2  •  C  \  C  •  CH3,  boils  at  55°. 
n-Propylacetylene,  C5H8  (4-pentine),  CH3  •  CHg  •  CH2  •  C  \  CH,  boils  at  48°. 

CH 

Isopropylacetylene,  C5H8  (3-methyl-l-butine),  CH3>CH'C  j  CH,  boils  at  28°. 

3 

Several  of  these  compounds  (the  first  three)  are  formed  during  the  dry 
distillation  of  coal  and  other  complex  substances,  and  are  hence  found  in  lighting 
gas. 

In  the  laboratory  they  are  obtained  by  the  following  methods  : 
(a)  By  electrolysing  acids  of  the  fumaric  acid  series  (see  later)  : 

COOH  •  CH  ;  CH  •  COOH  =  H2  +  2CO2  +  HC  :  CH. 

(6)  By  heating  with  alcoholic  potash  the  halogenated  compounds  (best 
the  bromo-derivatives),  CnH2nX2  and  CBH2n_.2X2,  gradual  elimination  of  halogen 
hydracid  (of  HBr  or,  in  presence  of  KOH,  of  KBr  and  H2O)  occurs  : 

C2H4Br2  =  HBr  +  C2H3Br >  HBr  +  C2H2. 

In  general,  starting  from  the  saturated  hydrocarbons,  CnH2n  +  2,  the  action 
of  halogen  and  elimination  of  halogen  hydracid  gives  an  unsaturated  hydrocarbon, 
CBH2n;  addition  of  halogen  to  this  and  subsequent  removal  of  halogen  hydracid 
gives  a  still  less  saturated  hydrocarbon,  CBH2n_2,  and  so  on. 

Elimination  of  2HC1  from  the  compounds  CBH2nCl2,  obtained  from  alde- 
hydes or  from  certain  ketones  (methylketones,  CBH2n+ 1  -  CO  •  CH3)  by  the  action 
of  PC15,  yields  always  a  trebly  linked  compound,  in  which,  however,  one  of 
the  carbon  atoms  is  always  united  to  a  single,  characteristic  hydrogen  atom  : 
—  C  ==  CH ;  for  example,  acetaldehyde  gives  ethylidene  chloride,  CH3  •  CHC12, 
which  then  yields  2HC1  +  CH  I  CH ;  while  acetone,  CH3  •  CO  •  CH3,  gives  chloro- 
acetone,  CH3  •  CC12  •  CH3,  and  this  2HC1  -f  CH3  •  C  =  CH,  the  elimination  of  halo- 
gen hydracid  never  occurring  in  such  a  way  as  to  give  compounds  with  two 
double  linkings,  such  as  CH2  :  C  :  CH2. 

Acetylene  derivatives  are  obtained  also  by  heating  the  acids  of  the  propiolic 
series  (see  later). 

Compounds  with  this  characteristic  hydrogen  atom  — C  =  CH  have  a  feebly 
acid  character  and  form  solid  metallic  derivatives  (acetylides)  when  treated 
with  an  ammoniacal  solution  of  copper  chloride  or  silver  nitrate  :  copper  acety- 
lide,  Cu  '  C  :  C  '  Cu,  H20,  having  a  reddish-brown  colour  and  apparently  the  con- 
stitution Cu2CH  •  CHO,  since  with  hydrogen  peroxide  it  gives  acetaldehyde, 
CH3 '  CHO  (Makowka,  1908) ;  and  silver  acetylide,  AgC  •  CAg,  which  is  white 
and  insoluble  in  water  or  ammonia  and,  in  the  dry  state,  is  extremely  explosive, 
simple  rubbing  being  sufficient  to  explode  it.  With  hydrochloric  acid  it 
regenerates  acetylene  in  a  pure  state. 


ACETYLENE  111 

The  proof  that  it  is  the  characteristic  hydrogen  atom  which  is  replaced 
by  metals  lies  in  the  fact  that  acetylene  derivatives  from  other  ketones  (not 
from  methylketones)  do  not  give  metallic  acetylides  : 

CH3  •  CH2  •  CO  •  CH2  •  CH3  ->  CH3  •  CH2  •  CC12  •  CH^  •  CH3 > 

2HC1  4-  CH3  •  C  i  C  •  CH2  •  CH3. 

Four  atoms  of  a  halogen  or  of  hydrogen  may  be  added  to  the  hydrocarbons 
of  the  acetylene  series,  saturated  compounds  being  formed ;  as  a  rule,  however, 
only  two  atoms  are  readily  added,  although  under  the  action  of  light  four  halogen 
atoms  may  be  added  almost  always. 

The  compounds  of  the  define  series  may,  however,  be  distinguished  from 
those  of  the  acetylene  series  by  means  of  the  ozone  reaction,  since  compounds 
with  a  triple  linking  do  not  fix  ozone  from  ozonised  air  at  all  (Molinari;  see 
p.  107). 

The  hydrocarbons  of  the  acetylene  series  take  up  a  molecule  of  water  in 
presence  of  mercury  salts,  giving  rise  to  complex  mercuric  compounds,  which, 
with  HC1,  give  as  final  product  an  aldehyde  or  ket(5ne  of  the  saturated  series  : 
CH3  •  C  i  CH  (allylene)  +  H20  =  CH3  •  CO  •  CH3  (acetone)  or  CH  !  CH  + 
H2O  =  CHg'CHO  (acetaldehyde).  The  last  reaction  serves  to  illustrate  the 
transformation  of  inorganic  into  organic  substances  (see  later,  chapter  on 
Alcohol). 

In  the  acetylene  series,  also,  condensation  or  polymerisation  is  possible,  three 
molecules  of  acetylene,  when  heated,  yielding  benzene,  C6H6 ;  three  molecules 
of  dimethylacetylene,  C4H6,  giving,  with  concentrated  sulphuric  acid,  hexa- 
methylbenzene,  C6(CH3)6,  and  allylene,  C3H4,  similarly  yielding  trimethylbenzene 
(mesitylene),  C6H3(CH3)3. 

In  the  higher  compounds,  the  position  of  the  triple  bond  is  deduced  from 
the  oxidation  products,  since,  as  with  substances  with  a  double  linking,  the 
breaking  of  the  chain  occurs  at  the  multiple  linking. 

When  certain  acetylene  derivatives,  e.  g.,  XC  =  C  *  CH3,  are  heated  with 
sodium,  the  triple  bond  changes  its  position,  the  products  being  sodium  deriva- 
tives of  isomeric  hydrocarbons,  X  •  CH2  •  C  :  CH  (these  give  metallic  acetylides, 
but  the  original  compounds  do  not);  when  these  are  heated  with  alcoholic 
potash,  the  reverse  change  occurs. 

ACETYLENE,  C2H2  (Ethine),  HC  :  CH.  Without  having  isolated  or  char- 
acterised this  compound,  Davy  obtained  it  in  1839  in  a  very  impure  condition, 
by  treating  with  water  the  product  obtained  by  heating  together  potassium 
carbonate  and  carbon,  which  should  yield  potassium.  Berthelot  first  obtained 
it  pure  (and  named  it)  in  1859,  by  passing  ethylene  or  alcohol  or  ether  vapour 
through  a  red-hot  tube ;  he  prepared  it  also  by  means  of  a  voltaic  arc  passing 
between  two  carbons  in  an  atmosphere  of  hydrogen.  In  1862,  Wohler  prepared 
it  by  treating  calcium  carbide  (obtained  by  heating  carbon  with  an  alloy  of 
zinc  and  calcium)  with  water. 

It  is  formed  in  the  incomplete  combustion  of  various  hydrocarbons  and 
of  illuminating  gas  (e.  g.,  in  the  flame  of  a  bunsen  burner  alight  at  the  bottom). 

The  industrial  preparation  of  acetylene  has  assumed  great  and  unforeseen 
practical  importance  since  1870,  when  it  became  possible  to  prepare  calcium 
carbide  on  an  enormous  industrial  scale  by  means  of  the  electric  furnace  (see 
"  Calcium  Carbide  Industry,"  Vol.  I.,  p.  638)  : 

C\ 

HI  >Ca  4-  2H20  =  Ca(OH)2  +  HC  !  CH. 

V 

Acetylene  is  a  colourless  gas,  sp.  gr.  0'92  (1  litre  weighs  1/165  grams),  with 
a  pleasant  odour  when  pure  and  a  disagreeable  one  when  impure  (as  usually 


112  ORGANIC    CHEMISTRY 

obtained).  At  -f-  1°  under  a  pressure  of  48  atmos.  it  forms  a  highly  refractive, 
mobile,  colourless  liquid,  sp.  gr.  0'451,  and,  on  evaporating  rapidly,  partially 
solidifies  in  the  form  of  snow,  m.-pt.  — 81°. 

One  volume  of  acetylene  gas  dissolves  in  I'l  vols.  of  water, -or  in  £  vol.  of 
alcohol  or  in  20  vols.  of  saturated  salt  solution;  1  litre  of  acetone  dissolves 
24  litres  of  acetylene,  or  300  litres  at  12  atmos.,  or  about  2000  litres  at  —80°, 
its  volume  being  then  increased  fourfold.  Permanganate  oxidises  it,  giving 
oxalic  acid,  and  chromic  acid  acetic  acid. 

It  is  an  endothermic  compound,  requiring  for  its  formation  from  its  elements, 
61,000  cals. ;  it  is  hence  very  unstable  and  is  readily  decomposed  by  the  detona- 
tion of  a  mercury  fulminate  cap  or  by  an  electric  discharge,  developing  as  much 
heat  as  an  equal  volume  of  hydrogen  on  conversion  into  water.  The  explosion 
takes  place  much  more  readily  and  is  much  more  dangerous  with  the  compressed 
gas  and  still  more  so  with  the  liquid. 

Acetylene  decomposes  at  780°  and,  when  mixed  with  air,  fgnites  at  480°. 
One  cubic  metre  (1'165  kilos)  of  acetylene,  in  burning,  develops  14,350  Cals. 
(12,300  Cals.  per  kilo),  whilst  ordinary  coal-gas  gives  about  5000  Cals. 

When  mixed  with  air  or,  better,  with  oxygen  it  forms  a  detonating  mixture 
which  explodes  with  great  energy  in  contact  with  an  ignited  body.  The 
explosion  is  violent  even  with  1  vol.  of  acetylene  and  40  vols.  of  air ;  it  reaches 
its  maximum  violence  with  1  vol.  of  the  gas  and  12  vols.  of  air  (2 '5  vols.  of 
oxygen),  whilst  scarcely  any  explosion  but  mere  burning  takes  place  with  1  vol. 
of  acetylene  and  1'3  vols.  of  air  (as  has  been  already  stated  on  p.  34,  ordinary 
illuminating  gas  only  explodes  when  at  least  1  vol.  is  present  to  about  20  vols. 
of  air). 

Explosive  mixtures  of  acetylene  are  more  dangerous  than  those  of  coal-gas 
owing  to  the  greater  speed  of  propagation  of  the  explosion  (e.  g.,  with  1  vol.  of 
acetylene  and  40  of  air),  the  explosive  force  being  thus  increased  (see  section 
on  Explosives) ;  further,  acetylene  contains  less  hydrogen  and  hence  forms 
less  water,  the  condensation  of  the  gases  resulting  from  the  explosion  being 
consequently  smaller.  The  wide  limits  of  the  explosive  mixtures  (from  2 '4 
to  130  vols.  of  acetylene  per  100  vols.  of  air)  are  explained  by  the  fact  that  this 
gas,  being  an  endothermic  compound,  reacts  or  decomposes  with  great  facility. 

In  contact  with  copper,  bronze,  silver,  etc.,  acetylene  readily  forms  explosive 
acetylides  (see  p.  110), x  but  when  perfectly  dry  does  not  attack  metals. 

It  was  at  first  thought  that  acetylene,  like  carbon  monoxide,  was  poisonous, 
but  experiments  made  during  the  last  few  years  have  shown  that  animals  do 
not  die  in  an  atmosphere  containing  9  per  cent,  or,  in  some  cases,  even  20  per 
cent,  of  the  gas.  When,  however,  the  acetylene  is  highly  contaminated  with 
sulphides  and  phosphides,  it  may  be  poisonous. 

With  an  ordinary  gas-jet,  acetylene  burns  with  a  reddish,  smoky  flame, 
but  by  passing  the  gas  at  a  pressure  of  60  mm.  through  two  jets  nearly  meeting 
at  an  angle,  a  white,  highly  luminous,  fan-shaped  flame  is  obtained  without 
the  dark  middle  portion  of  the  ordinary  bat's- wing  coal-gas  flame. 

One  kilo  of  chemically  pure  calcium  carbide  should  yield  theoretically  349  litres  of 
acetylene,  and  good  commercial  carbide  yields  practically  300  litres.  The  luminosity  of 

1  The  ready  formation  of  metallic  acetylides,  especially  that  of  copper,  led  Erdmann  (1907) 
to  devise  a  rapid  and  exact  analytical  method  for  the  direct  quantitative  precipitation  of  copper 
from  any  solution  and  in  presence  of  any  metals  (except  Ag,  Hg,  An,  Pd,  and  Os,  which  must  be 
previously  eliminated ) :  the  feebly  alkaline  solution  of  the  copper  salt  is  reduced  until  decolorised 
with  hydroxylamine  hydrochloride,  C2H2  being  then  passed  through  and  the  precipitated  copper 
acetylide  collected  on  a  filter,  washed  with  water  and  pumped  off ;  together  with  the  filter-paper 
it  is  introduced  into  a  porcelain  crucible,  treated  with  10  to  15  c.c.  of  dilute  nitric  acid  (sp.  gr. 
1-15)  and  eight  to  ten  drops  of  concentrated  nitric  acid  (sp.  gr.  1-52),  dried  on  a  water-bath, 
heated  rapidly  to  redness  and  weighed  as  CuO.  The  acetylene  used  for  this  precipitation  should 
be  washed  with  lead  acetate  solution. 


USES    OF    ACETYLENE  113 

acetylene  in  comparison  with  that  of  other  substances  has  already  been  referred  to  on  p.  64. 
A  proportion  of  2  vols.  of  air  to  3  of  acetylene  gives  the  maximum  luminosity,  and  at  the 
present  time  special  incandescent  mantles  are  made  for  use  with  acetylene. 

The  impurities  present  in  ordinary  acetylene  (98  to  99  per  cent,  purity)  are :  N,  NH3, 
CO,  H2S,  and  PH3,  the  last  three  of  which  are  poisonous.  The  gas  is  purified  by  passing 
it  through  an  acid  solution  of  a  metallic  salt. 

Lunge  and  Cederkreutz  recommend  chloride  of  lime  (hypochlorite)  for  purifying  acety- 
lene, care  being  taken  that  the  mass  does  not  heat,  as  this  would  be  dangerous.  Latterly 
it  has  been  suggested  to  fix  the  PH3  by  passing  the  gas  through  concentrated  sulphuric 
acid  (64°  Be.)  saturated  with  As2O3.  A  good  purifying  material  is  made  by  preparing 
a  paste  of  calcium  hypochlorite,  quicklime,  sodium  silicate,  and  powdered  calcium  carbide, 
this  remaining  porous  when  allowed  to  dry  in  the  air. 

USES.  When  the  great  calcium  carbide  industry  was  started,  it  appeared  as 
though  acetylene  would  be  used  solely  as  a  competitor  of  illuminating  gas,  electricity, 
petroleum,  etc.,  but  most  of  the  acetylene  is  now  employed  in  cutting  metals,  while 
calcium  carbide  is  largely  used  for  the  manufacture  of  calcium  cyanamide  (see  Vol.  I., 
p.  371). 

The  use  of  liquid  acetylene  would  be  very  convenient,  but  is  highly  dangerous,  since 
a  sharp  blow  or  other  accident  might  easily  produce  a  terrible  explosion. 

It  is  still  too  expensive  to  employ  in  place  of  benzene  for  carburetting  coal-gas.  Dis- 
solved in  acetone  (Claude  and  Hess,  1896),  which  dissolves  a  large  quantity  of  it  (vide  infra), 
it  is  used  to  great  advantage  for  the  oxy '-acetylene  blowpipe  in  place  of  oxy-hydrogen.  With 
the  latter,  for  every  cubic  metre  of  oxygen  4  cu.  metres  of  hydrogen  are  used 
practically  (theoretically  2  cu.  metres),  whilst  the  same  amount  of  oxygen  burns 
'with  600  litres  of  acetylene  (theoretically  400  litres),  which  costs  much  less  than  4  cu. 
metres  of  hydrogen.  The  oxy-acetylene  flame  exhibits  at  the  centre  a  shining  point,  which 
has  a  temperature  of  2800°  to  3000°,  and  to  weld  iron  sheets  1  mm.  thick  requires  50  to  75 
litres  of  acetylene  per  hour,  5  metres  being  welded  in  this  time. 

With  a  slight  excess  of  oxygen  large  tubes  are  easily  cut  and  steel  blocks  perforated. 

Acetylene  dissolved  in  acetone,  especially  if  the  solution  is  ab  orbed  by  porous  material, 
is  not  at  all  dangerous  and  may  be  transported  in  iron  cylinders. 

In  moderate  quantities  acetylene  dissolved  in  acetone  is  sold  compressed  in  iron  bottles 
capable  of  yielding  650  litres  of  the  gas;  these  bottles  are  convenient  for  lighting  mines, 
railway  carriages,  automobiles,  etc.  In  the  United  States  300,000  of  such  bottles  were 
used  in  1913,  while  in  Germany  6000  were  used  for  automobiles  alone. 

Acetylene  is  utilised  in  the  preparation  of  numerous  chloro-derivatives  which  have 
various  practical  applications,  e.  g.,  in  the  manufacture  of  indigo,  acetaldehyde,  acetic 
acid,  and  alcohol  (see  below).  It  is  used  also  in  the  synthesis  of  thiophene  (Steinkopf's 
method  :  see  chapter  on  Thiophene),  and  also  in  that  of  rubber  (according  to  Heinemann) ; 
when  heated,  a  mixture  of  acetylene  and  ethylene  condenses  to  butandiene,  CH2  :  CH  •  CH  : 
CH2,  this  being  converted  by  methylation  into  isoprene,  CH2  :  C(CH3)  •  CH  :  CH2, 
which  is  polymerised  by  concentrated  hydrochloric  acid  with  formation  of  synthetic 
rubber. 

By  repeated  passage  of  a  mixture  in  equal  volumes  of  acetylene  and  hydrogen  through 
tubes  heated  electrically  to  650°  to  800°,  considerable  polymerisation  of  the  acetylene  is 
effected  with  formation  of  about  60  per  cent,  of  tar  containing  20  per  cent,  of  benzene, 
a  certain  amount  of  naphthalene,  and  a  little  toluene,  anthracene,  diphenyl,  fluorene,  etc. 
(R.  Meyer,  1912). 

Large  quantities  of  acetylene  are  decomposed  by  the  electric  discharge  to  make  very 
pure  hydrogen  and  lamp-black  (see  Vol.  I.,  pp.  142, 458 ;  also  B.  P.  Pictet's  Ger.  Pat.  255,733, 
1909). 

The  hope  of  manufacturing  synthetic  alcohol  economically  from  acetylene  had  died  out, 
but  during  the  European  War  the  enormous  rise  in  the  price  of  alcohol  turned  attention  to 
this  synthesis,  although  the  industrial  experiments  which  followed  could  not  be  sustained 
in  normal  times  (see  later  :  Alcohol). 

Even  for  engines  it  is  still  too  dear  to  use.     Acetylene  can,  however,  be  used  conveniently 

with  a  rational  plant  and  relatively  small  gasometers  connected  with  iron  tubes  which  carry 

the  gas  direct  to  the  burners  (when  prepared  from  pure  carbide),  but  it  is  necessary  to 

avoid  the  use  of  copper  or  bronze  in  any  part  of  the  gasometers,  pipes,  and  taps,  in 

VOL.  II.  8 


114  ORGANIC    CHEMISTRY 

order  to   avoid   explosions,  which  are  almost  always   due  to  the  formation  of  copper 
acetylide.1 

In  testing  the  purity  of  acetylene  the  only  quantitative  determination  usually  made  is 
that  of  the  hydrogen  phosphide,  which  should  not  occur  in  greater  proportion  than  1  gram 
per  cubic  metre,  since,  besides  being  poisonous  and  having  an  unpleasant  smell,  it  facilitates 
the  formation  of  explosive  metallic  acetylides.  (The  estimation-of  the  impurities  in  carbide 
is  described  in  Vol.  L,  p.  639.) 

III.  HYDROCARBONS   OF  THE  SERIES,  CnH2n_4  and  CnH2n_6 

DI ACETYLENE,  C4H2  (Butandiine),  CH  i  C  •  C  :  CH,  is  a  gas  and  forms  the  usual 
metallic  acetylides. 

DIPROPARGYL,  C6H6  (Hexan-1 :  5-diine),  CH  i  C'CH2'CH2-C  \  CH,  is  isomeric 
with  benzene,  boils  at  85°,  and  can  take  up  8  atoms  of  bromine.  It  is  obtained  from  diallyl, 
C6H10,  and  readily  forms  metallic  acetylides. 

HEXAN-2  :  4-DIINE,  CH3  •  C  ':  C  •  C  ':  C'  CH3>  is  also  isomeric  with  benzene. 

BB.     HALOGEN    DERIVATIVES    OF   THE    HYDRO- 
CARBONS 

The  Table  on  page  115  summarises  the  physical  properties  of  the  more 
important  halogen  derivatives  of  the  hydrocarbons,  the  first  column  giving 
the  hydrocarbon  residue  (alkyl)  united  with  the  halogen. 

I.  HALOGEN   DERIVATIVES   OF  SATURATED   HYDROCARBONS 

PROPERTIES.  Very  few  are  gases,  several  are  liquids,  and  those  which 
contain  many  atoms  in  the  molecule  are  solids.  The  iodo-compounds  boil 
at  higher  temperatures  than  the  corresponding  bromo-  and  chloro-compounds. 
They  are  very  slightly,  if  at  all,  soluble  in  water,  but  are  readily  soluble  in 
alcohol,  ether,  and  glacial  acetic  acid. 

Most  of  them  burn  easily,  and  ethyl  and  methyl  chlorides  colour  the  edges 
of  the  flame  green.  Some  of  them,  containing  few  carbon  atoms,  produce 
ancesfliesia,  e.  g.,  CHC13,  CH2C12,  C2H3C13,  C2H5Br,  C2H5C1. 

Generally  they  do  not  react  with  silver  nitrate,  since  these  compounds  are 
not  dissociated  in  solution,  and  do  not  give  free  halogen  ions  (see  Vol.  I.,  pp. 
96,  98  et  seq.).  In  alcoholic  solution,  ethyl  iodide  gives  a  little  precipitate  in 
the  cold,  and  ethyl  bromide  in  the  hot,  whilst  the  chloride  gives  no  precipitate 
at  all,  with  silver  nitrate. 

The  bromo-  and  iodo-compounds  exhibit  great  reactivity  and  effect  the 
most  varied  and  interesting  reactions  and  syntheses;  methyl  iodide  reacts 
the  most  readily  of  all,  the  reactivity  diminishing  with  increase  of  molecular 
weight. 

The  halogens  of  these  compounds  may  easily  be  replaced  by  H  (by  sodium - 
amalgam,  or  zinc  dust  and  hydrochloric  or  acetic  acid). 

1  The  numerous  types  of  apparatus  for  generating  acetylene  may  be  divided  into  three  groups  : 

(1)  Those  where  the  carbide  and  water  are  in  separate  vessels  communicating  by  a  tube 
furnished  with  a  tap  which  automatically  opens  more  or  less  and  so  diminishes  or  increases  the 
supply  of  the  gas.     To  prevent  the  carbide,  or  rather  the  lime  formed,  from  holding  water  and 
generating  gas  even  after  the  tap  is  closed,  the  carbide  is  impregnated  with  an  indifferent  sub- 
stance, e.  g.,  paraffin  wax,  stearine,  oil,  sugar  (to  dissolve  the  lime  as  calcium  saccharate),  etc. 
One  inconvenience  of  this  procedure  is  that  at'some  places  the  carbide,  in  presence  of  little  water, 
becomes  excessively  heated  and  may  produce  an  explosion,  which  is  dangerous  if  the  gas  is  under 
pressure. 

(2)  Those  where  the  carbide  is  suspended  at  a  certain  part  of  the  vessel  containing  the  water; 
acetylene  is  then  generated  when  the  level  of  the  water  rises  to  the  carbide  and  ceases  automatic- 
ally when  it  falls. 

(3)  Those  where  the  carbide  and  water  are  separated,  a  small  quantity  of  carbide  being  dropped 
into  excess  of  water.     This  would  be  the  most  rational  method,  but  is  perhaps  not  the  most 
convenient  owing  to  the  difficulty  of  powdering  the  carbide  (often  very  hard)  without  allowing 
it  to  absorb  moisture. 


HALOGENATED    PARAFFINS 


115 


These  derivatives  may,  to  some  extent,  be  transformed  one  into  the  other, 
e.  g.,  the  chlorides  into  iodides  by  treatment  with  KI  or  CaI2,  and  the  iodides 
into  the  fluorides  (more  volatile  than  the  chlorides)  by  means  of  silver  fluoride. 


Alkyl 

Names  of  the  Alkyls 
and  Isomerides 

Chlorides 

Bromides 

Iodides 

B.-pt. 

Sp.gr. 

B.-pt. 

Sp.  gr. 

B.-pt. 

Sp.  gr. 

a    SATUEATED 

DERIVATIVES 

(1)  Afonosubslituted 

CH3 

Methyl 

-  23-7° 

0-952  (0°) 

+  4-5° 

1-732  (0°) 

+  45° 

2-293  (18°) 

C2H5 

Ethyl 

+  12-2° 

0-918  (0°) 

38-4° 

1-468  (13°) 

+  72-3° 

1-944  (14°) 

C3H7 

n-Propyl 

+  46-5° 

0-912  (0°) 

71° 

1-383  (0°) 

102-5° 

1-786  (0°) 

Isopropyl 

36-5° 

0-882  (0°) 

60° 

1-340  (0°) 

89° 

1-744  (0°) 

C4H9 

n-Butyl  (primary) 

78° 

0-907  (0°) 

101° 

1-305  (0°) 

130° 

1-643  (0°) 

Isobutyl 

68-5° 

0-895  (0°) 

92° 

1-204  (16°) 

119° 

1-640  (0°) 

sec.-Butyl   . 

— 

— 

— 

— 

119-120° 

1-626  (0°) 

tert.-Butyl 

55° 

0-866  (0°) 

72° 

1-215  (20°) 

100° 

1-571  (0°) 

CjHji 

n-Amyl  (primary) 

107° 

0-901  (0°) 

129° 

1-246  (0°) 

156° 

1-543  (0°) 

Isoamyl,  (OH3)2  :  CH- 

101° 

0-893  (0°) 

121° 

1-236  (0°) 

148° 

1-468  (0°) 

OH2-OH2-X 

tertiary-Butylmethyl 

— 

0-879  (0°) 

— 

1-225  (0°) 

— 

1-050  ?(0°) 

(CH3)3(C-OH2-X 

active-  Amyl 

97-99° 

0-886  (15°) 

118-120° 

1-221  (20°) 

148° 

1-524  (20°) 

06H13 

(OH2)(02H6)OH-CH2-X 
n-Hexyl  (primary) 

134° 

0-892  (16°) 

156° 

1-193  (0°) 

182° 

1-461  (0°) 

C8H17 

n-Hexyl  (secondary) 
n-Heptyl  (primary) 
n-Octyl  (primary) 

159° 

180° 

0-881  (16°) 
0-880  (16°) 

144° 
179° 
199° 

1-113  (16°) 
1-116  (16°) 

168° 
201° 
221° 

1-453  (0°) 
1-386  (16°) 
1-345  (16°) 

(2)  Disubstituted 

>CH2 

Methylene,  CH2X2 

42° 

— 

97° 

— 

180° 

— 

-CH2-CH2- 

Ethylene 

84° 

—  . 

131° 

— 

— 

—  . 

CH3-CH2< 

Ethylidene  (or  ethydene) 

57° 

— 

108° 

— 

— 

— 

(3)  Trisubslituted 

CHX3  (chloroform, 

61° 

— 

151° 

— 

solid 

— 

bromoform,  iodoform) 

m.-pt.  119° 

CH3'CC13    methylchloro- 

74° 

•  —  . 

188° 

— 

— 

—  • 

form  (a-trichloroethane) 

CHjjCl-CHCljj  (/3-tri- 

114° 

— 

220° 

•  —  - 

— 

— 

chloroethane) 

CH2X-OHX-OH2X     (tri- 

158° 

— 

— 

— 

— 

— 

chlorohydrin,             tri- 

bromohydrin) 

(4)  Polysubstituted 

OX4  (carbon  tetra- 

77° 

— 

— 

— 

solid 

— 

chloride,  iodide) 

C201g  perchloroethane 

solid 

— 

— 

•  — 

— 

— 

m.-pt.  187° 

(6)  UNSATURATED 

DERIVATIVES 

(1)  Ethylenic  series 

OS,  :  CH-X 

Vinyl  chloride,  etc. 

-18° 

— 

23° 

— 

56° 

— 

Allvl 

46° 

70° 

101° 

C2H2_:X2 

**-it-j  *           ,, 
Dichloroethylene 

55° 

— 

— 

— 

C2H  •  X3 

Trichloroethylene 

88° 

— 

— 

— 

— 

— 

n     •   ~v 

O2    ;    A.4 

Tetrachloroethylene 

121° 

— 

— 

— 

— 

— 

(2)'  Acetylene  series 

no  ;  ox 

Monochloro-  and  mono- 

gas 

— 

gas 



— 

— 

bromo-acetylene 

i 

METHODS  OF  PREPARATION,  (a)  By  the  action  of  halogens  on  satur- 
ated hydrocarbons  :  chlorine  and  bromine  react  directly  at  the  ordinary 
temperature  on  the  gaseous  hydrocarbons,  and  on  heating  with  the  liquid  ones. 

The  first  halogen  atom  is  fixed  more  readily  than  the  succeeding  ones,  and 
the  addition  of  iodine  facilitates  the  reaction  with  bromine  and  chlorine,  since 
the  iodine  forms,  for  example,  IC13,  which  readily  gives  nascent  chlorine,  IC13  = 
IC1  -f  C12  (i.  e.,  it  acts  like  Sb015,  which  yields  SbCl3  -f  C12).  By  saturating 
with  chlorine  and  heating  under  pressure  energetic  chlorinations  may  be  affected. 

Methane,  ethane,  propane,  etc.,  exchange  their  hydrogen  atoms  one  by 
one  for  chlorine  atoms,  the  completely  substituted  compounds  (C2C16,  C3C18,  etc., 
and  especially  the  higher  ones),  on  further  energetic  chlorination,  being  resolved 


116  ORGANIC    CHEMISTRY 

into  other  completely  chlorinated  compounds  containing  less  numbers  of  carbon 
atoms:  C2C16  +  C12  =  2CC14 ;  C3C18  +  C12  =  C2C16  +  CC14,  a  little  hexa- 
chlorobenzene,  etc.,  being  always  formed  as  well. 

Iodine  scarcely  ever  acts  directly  on  the  hydrocarbons,  since  the  HI  formed 
acts  in  the  opposite  sense  on  the  iodo -products.  The  reaction  proceeds  only 
in  presence  of  iodic  acid  or  mercuric  oxide,  which  fixes  the  hydriodic  acid  as 
it  is  formed. 

The  iodo-compounds  are  easily  obtained  from  zinc-alkyls  and  iodine. 

When  the  halogens  act  directly,  the  more  energetic  (F  or  Cl)  replaces  the 
weaker  (Br  or  I).  The  iodo-compounds  may,  however,  be  easily  obtained  by 
first  preparing  the  magnesium  compounds  of  the  alkyl  chlorides  or  bromides 
and  treating  these  with  iodine  : 

Alkyl-Mg-Cl  +  I2  =  Alkyl-I  +  MglCl. 

(b)  Unsaturated  hydrocarbons,  with  the  halogen  hydracids,  give  saturated 
monosubstituted  derivatives  :    C2H4  +  HBr  —  C2H5Br,  ethyl  bromide,  etc. ; 
if  the  halogens  act  directly,  disubstituted  saturated  products  are  obtained  : 
C2H4  -f-  C12  =  C2H4C12,  ethylene  dichloride. 

Propylene,  CH3  •  CH :  CH2,  reacts  with  HI,  giving  isopropyl  iodide, 
CH3  •  CHI  •  CH3,  which  is  decomposed  by  alcoholic  potash,  yielding  propylene ; 
normal  propyl  iodide,  CH3  •  CH2  •  CH2I,  which  also  yields  propylene  when  HI  is 
removed  from  it,  may  thus  be  converted  into  isopropyl  iodide. 

Similar  behaviour  is  exhibited  by  the  butyl  iodides. 

The  halogen  always  goes  to  the  carbon  atom  united  with  the  lesser  number  of 
hydrogen  atoms  :  CH3  •  CH  :  CH2  +  HI-  =  CH3  •  CHI  •  CH3. 

(c)  The  alcohols,  CnH2n+1OH,  with  the  halogen  hydracids  give  :   CnH2n+1OH 
+  HBr  =  H2O  -f-  CnH2n+1Br,  but  the  reverse   action  also  proceeds,  and  to 
limit  this,  excess  of  the  halogen  hydracid  is  used  and  the  water  formed  is  fixed, 
e.  g.,  by  addition  of  zinc  chloride. 

Further,  the  chlorine  of  the  phosphorus  chlorides  also  replaces  hydroxyl : 
PC13  -f  3C2H5OH  =  P(OH)3  +  3C2H5C1,  or,  better,  PC15  +  C2H5OH  =  POC13 
+  HC1  -f-  C2H5C1.  This  reaction  is  of  importance  for  the  preparation  of  the 
bromo-  and  iodo-compounds  :  3CH3  •  OH  -f  P  +  31  =  3CH3I  +  H3P03 ;  the 
bromine  or  iodine  first  acts  on  the  phosphorus  to  form  PBr3  or  PI3,  this  then 
reacting  with  the  alcohol. 

The  polyhydric  alcohols  act  in  the  same  way;  for  example,  glycerol, 
C3H5(OH)3,  reacts  with  PC15,  giving  trichlorohydrin,  CH2C1  •  CHC1  •  CH2C1. 

The  resulting  halogenated  products  are  easily  separated  by  distillation, 
as  the  phosphorous  acid  does  not  distil.  In  these,  as  in  most  other  chemical 
reactions,  secondary  products  are  always  formed ;  these  are  often  very  complex, 
and  form  viscous  resins  of  unknown  composition. 

(d)  The  aldehydes  and  ketones  yield  disubstituted  products  :   for  example, 
ethylidene  chloride,  CH3  •  CHC12,  is  obtained  from  acetaldehyde,  CH3  •  CHO, 
and  dichloropropane,    CH3  •  CC12  •  CH3,  from   acetone,  CH3  •  CO  •  CH3,  by  the 
action  of  PC1S. 

METHYL  CHLORIDE  (Chloromethane),  CH3C1.  This  is  prepared  by 
passing  hydrogen  chloride  into  boiling  methyl  alcohol  containing  half  its  weight 
of  zinc  chloride  in  solution,  or  by  heating  1  part  of  methyl  alcohol  with  3  parts 
of  concentrated  sulphuric  acid  and  2  parts  of  concentrated  hydrochloric  acid. 
Industrially  it  may  be  obtained  by  heating  methyl  alcohol  and  crude,  concen- 
trated hydrochloric  acid  together  in  an  autoclave,  the  mass  issuing  from  the 
hot  autoclave  as  gas  being  washed  with  water  and  concentrated  hydrochloric 
acid  and  the  residual  dry  chloromethane  liquefied  by  cooling  at  the  pressure  of 
the  autoclave  itself.  Douane  (U.S.  Pat.  777,406)  suggested  an  apparatus  for 
continuous  manufacture. 


ALKYLHALIDES  117 

It  is  also  obtained  to-day  in  appreciable  quantity,  by  the  old  Vincent  process, 
from  the  final  residues  of  the  beet-sugar  industry,  which  are  evaporated  and 
then  dry-distilled.  In  this  way  an  abundant  quantity  of  trimethylamine  is 
formed ;  this  is  neutralised  with  HC1,  and  the  hydrochloride  distilled  at  300°. 
A  regular  evolution  of  methyl  chloride  and  trimethylamine  is  thus  obtained : 

3N(CH3)3HC1  =  2CH3C1  +  2N(CH3)3  +  CH3  •  NH2,  HC1. 

Trimetbylamine  hydro-  Trimethyl-  Methylamine  hydro-  , 

chloride  amine  chloride  (residue) 

The  chloromethane,  distilled  as  a  gas,  is  purified  with  HC1,  dried  with  CaCl2, 
and  liquefied  in  steel  cylinders  under  pressure,  just  as  is  done  with  carbon  dioxide 
(Vol.  L,  p.  480). 

It  is  a  colourless  gas  of  ethereal  odour,  and  at  —24 '09°  becomes  liquid,  then 
having  the  sp.  gr.  0*952  (at  0°).  Water  dissolves  one-fourth  of  its  volume, 
and  alcohol  rather  more.  It  burns  with  a  green-edged  flame.  - 

In  the  liquefied  condition  it  is  used  as  a  local  anaesthetic ;  it  is  used  also 
to  extract  perfumes  from  flowers^  and  in  considerable  quantities  for  the  manu- 
facture of  dyestuffs  (methyl  green),  especially  for  methylation,  but  the  greatest 
amount  is  employed  in  cooling  machines.  In  France  there  are  about  100  ice- 
machines  which  use  methyl  chloride  instead  of  liquefied  NH3,  C02,  or.  S02. 
In  brass  cylinders  containing  from  1  to  30  kilos  it  is  sold  at  11s.  to  14s.  Qd.  per 
kilo,  in  addition  to  the  cost  of  the  cylinder,  which  is  20s.  for  the  1-kilo,  25s.  6d. 
for  the  3-kilo,  and  £3  16s.  for  the  30-kilo  size. 

METHYL  IODIDE,  CH3I,  is  prepared  from  methyl  alcohol,  phosphorus,  and  iodine 
as  described  later  for  ethyl  iodide.  It  is  a  liquid  of  sp.  gr.  2-293,  boiling  at  45° ;  with  excess 
of  water  at  100°  it  is  decomposed  into  hydrogen  iodide  and  methyl  alcohol. 

ETHYL  CHLORIDE  (Chloroethane),  C2H5C1,  was  termed  by  Basil  Valentine  "  Spiritus 
salis  et  vini,"  or  spirit  of  sweet  wine.  It  is  obtained  from  ethane  and  chlorine,  or  by  passing 
hydrogen  chloride  into  a  solution  of  zinc  chloride  and  ethyl  alcohol.  It  is  formed  also  as 
a  secondary  product  in  the  manufacture  of  chloral.  It  boils  at  +  12-2°  and  burns  with  a 
flame  having  green  edges.  It  is  a  local  anaesthetic  and  is  soluble  in  alcohol,  but  only  slightly 
so  in  water.  It  costs  from  Is.  Id.  to  4s.  per  kilo  in  metal  cylinders  containing  1  to  30  kilos. 

ETHYL  IODIDE,  C2H5I,  is  prepared  by  digesting  10  grams  of  red  phosphorus  with  80 
grams  of  absolute  alcohol  for  twelve  hours  and  gradually  adding  100  grams  of  iodine ;  the 
mixture  is  then  heated  for  two  hours  under  a  reflux  condenser  and  the  ethyl  iodide  distilled 
on  the  water-bath,  washed  with  dilute  alkali  and  with  water,  and  dried  by  means  of  calcium 
chloride.  When  yellow  instead  of  red  phosphorus  is  used,  much  less  of  it  is  required  and 
the  reaction  is  more  rapid,  boiling  being  unnecessary;  yellow  phosphorus  is,  however, 
inconvenient  to  work  with.  From  3  to  4  kilos  of  ethyl  iodide  are  obtained  from  3  kilos  of 
iodine.  According  to  Ger.  Pat.  175,209,  ethyl  iodide  is  obtained  quantitatively  if  diethyl 
sulphate  is  slowly  added  to  the  calculated  amount  of  hot  potassium  iodide  solution.  It 
boils  at  72-3°  and  has  the  sp.  gr.  1-944  (at  14°) ;  it  is  highly  refractive  and  dissolves  in  alcohol 
or  ether.  It  decomposes  when  heated  with  water  at  100°.  Chlorine  converts  it  into  ethyl 
chloride  and  bromine  into  ethyl  bromide.  In  the  light  it  slowly  decomposes  with  separation 
of  iodine,  which  colours  the  liquid  brown,  but  it  remains  colourless  in  presence  of  a  drop 
of  mercury.  It  is  used  as  an  inhalation  for  the  treatment  of  asthma.  It  costs  about  28s. 
to  32s.  per  kilo. 

ETHYL  FLUORIDE,  C2H5F,  is  liquid,  at  —48°,  burns  with  a  blue  flame,  and  does  not 
attack  glass. 

From  PROPANE  two  series  of  isomeric  compounds  are  derived  :  CH3  •  CH2  •  CH2X, 
prepared  from  normal  propyl  alcohol,  and  CH3  •  CHX  •  CH3,  derived  from  isopropyl  alcohol, 
and  hence  from  acetone. 

ISOPROPYL  IODIDE  (Iodo-2-propane)  CH3  •  CHI  •  CH3,  is  obtained  from  glycerol, 
phosphorus  and  iodine,  small  amounts  of  allyl  iodide  and  propylene  being  also  formed. 

The  butyl  compounds  occur  in  four  isomeric  modifications  : 

NORMAL  BUTYL  IODIDE  (Iodo-i-butane),  CH3  •  CH2  •  CH2  •  CH2I. 

SECONDARY  BUTYL  IODIDE  (Iodo-2-butane),  CH3  •  CH2  •  CHI  •  CH3. 


118 

PTT 

ISOBUTYL  IODIDE  (Methyl-2-iodo-s-propane),  ,±3>CH  •  CHJ. 

«^±13 

PTT 
TERTIARY  BUTYL  IODIDE  (Methyl-2-iodo-2-propane),  ^3>CI  •  CHy 

l^llg 

The  constitutions  of  the  four  isomerides  are  deduced  from  those  of  the  corresponding 
butyl  alcohols,  from  which  they  are  obtained  by  the  action  of  hydriodic  acid. 

Of  the  AMYL  derivatives  eight  isomerides  are  known. 

METHYLENE  CHLORIDE  (Dichloromethane),  CH2C12,  bromide  and  iodide  (see  Table, 
p.  115). 

ETHYLENE  COMPOUNDS,  CH2X  •  CH2X,  are  formed  from  ethylene  by  the  addition 
of  halogens  or  from  glycol,  C2H4(OH)2  and  halogen  hydracids. 

ETHYLIDENE  (or  Ethydene)  COMPOUNDS,  CH2  •  CHX2,  are  obtained  by  sub- 
stituting the  oxygen  of  the  aldehydes  by  halogens. 

ETHYLENE  CHLORIDE  (Dichloro-i  :  2-ethane),  CH2C1  •  CH2C1  (Dutch  liquid,  1795) 
boils  at  84°.  The  IODIDE,  BROMIDE,  and  CHLORIDE  with  alcoholic  potash  give 
acetylene  and  glycol. 

ETHYLIDENE  CHLORIDE  (Ethydene  chloride  or  Dichloro-i  :  i-ethane), 
CH3  •  CHC12,  is  obtained  from  aldehyde  and  phosgene  :  CH3  •  CHO  +  COC12  =  CO2  + 
CH3  •  CHC12,  chloral  (which  see)  being  also  formed ;  it  boils  at  57°. 

CHLOROFORM  (Trichloromethane),  CHC13.  Chloroform  was  discovered 
by  Liebig  and  Souberain  and  its  constitution  shown  by  Dumas  in  1835. 

It  is  a  colourless  liquid  with  a  sweet  ethereal  smell  and  taste ;  it  dissolves 
only  to  a  slight  extent  in  water  (0*7  per  cent.),  but  is  soluble  in  alcohol  or  ether. 
It  boils  at  61'2°,  and  its  vapour  pressure  at  20°  is  160  mm.  of  mercury;  its 
specific  gravity  is  1*5263  at  0°  and  1*500  at  15°,  referred  to  water  at  4°. 

It  is  non-inflammable,  and  it  dissolves  resins,  rubber,  fats,  and  iodine,  with 
the  last  of  which  it  gives  violet  solutions. 

Chromic  acid  transforms  chloroform  into  phosgene  (COC12),  while  potassium 
amalgam  gives  acetylene.  With  potassium  hydroxide  it  gives  potassium 
formate  and  chloride  : 

CHC13  +  4KOH  =  3KC1  +  H  •  C02K  +  2H2O. 

With  ammonia  at  a  red  heat  it  gives  hydrocyanic  and  hydrochloric  acids  : 
CHC13  +  NH3  =  HCN  +  3HC1. 

Exposed  to  light  and  air,  it  decomposes  partially  into  Cl,  HC1,  and  COC12, 
but  it  can  be  kept  in  yellow  bottles,  while  that  for  pharmaceutical  use  keeps 
better  if  1  per  cent,  of  absolute  alcohol  is  added.  The  presence  in  it  of  more 
than  1  per  cent,  of  alcohol  is  shown  by  shaking  the  chloroform  in  a  test-tube 
with  a  granule  of  pure  permanganate,  a  yellowish-brown  spot  forming  round 
the  latter  and  also  on  the  glass  where  it  rests. 

It  is  the  most  efficacious  anaesthetic  (Simpson,  1848),  but  in  some  cases 
may  cause  death  if  not  used  with  great  care,  since  it  acts  on  the  heart ;  to 
diminish  this  effect,  it  is  mixed  with  atropine  or  morphine.1  The  harmful 

1  From  coal-tar  products  various  anaesthetics  or  hypnotics  are  produced  synthetically,  and 
these  have  been  of  great  service  to  medicine,  especially  to  surgery,  rendering  possible  the  execution 
of  the  most  complicated  operations  without  any  pain  to  the  patient.  At  first  substances  were 
used  which  produced  general  anaesthesia  of  the  organism,  but  they  were  accompanied  by  many 
inconveniences,  sometimes  by  fatal  results. 

Indeed,  the  anaesthetic  is  transported  by  the  blood  into  contact  with  the  higher  nervous  centres 
by  which  pain  is  felt,  producing  poisoning  and  paralysis  of  them,  often  lasting  for  some  time; 
at  the  same  time  an  influence  is  felt  by  the  centres  controlling  the  action  of  the  heart  and  of  respira- 
tion, this  being  the  cause  of  the  danger  and  disturbance  produced  by  general  anaesthesia.  The 
nerve-currents  start  from  the  periphery,  from  the  points  where  the  surgical  operation  is  to  begin, 
and  are  transmitted  to  the  brain,  which  transforms  them  into  painful  sensations,  and  it  is  by 
influencing  the  cerebral  centres  by  anaesthetics  that  pain  is  avoided ;  anaesthesia  ceases,  however, 
to  be  dangerous  if  the  peripheral  nervous  centres  at  the  beginning  of  the  nerve-currents  are 
paralysed  without  the  latter  reaching  the  brain.  Thus  local  anaesthesia  is  much  more  rational 


CHLOROFORM  119 

effects  of  chloroform  are  due  sometimes  to  its  decomposition  products,  especially 
to  phosgene,  COC12. 

The  use  of  chloroform  has  been  suggested  to  render  pigs  insensible,  so  as  to 
kill  them  painlessly  and  to  skin  them  more  easily.  Also,  in  fattening  them, 
they  are  subjected  to  periodic  inhalations  of  chloroform,  which  renders  them 
more  restful. 

Chloroform  is  sometimes  used  for  dissolving  rubber  and  gutta-percha,  for 
extracting  alkaloids  and  ethereal  oils,  and,  together  with  acetone  and  alkali, 
for  preparing  acetone-chloroform  or  chloretone,  which  has  a  slight  camphor-like 
odour,  melts  at  80°  to  81°,  and  serves  as  a  hypnotic,  as  a  local  anaesthetic  and 
as  an  antiseptic. 

PREPARATION.  It  is  prepared  from  (1)  ethyl  alcohol  or  (2)  acetone,  by  heating 
with  chloride  of  lime  and  water.  In  the  former  case  there  is  always  an  appreciable  evolution 
of  CO2,  which  originates  in  the  oxidation  of  the  alcohol,  and  liberates  HC1O  and  so  forms 
aldehyde  and  hence  chloral,  CC13  •  CHO,  this,  in  presence  of  lime,  yielding  chloroform  and 
calcium  formate  :  2CC13  •  CHO  +  Ca(OH)2  =  2CHC13  +  Ca(HC02)2.  If  the  decomposition 
of  the  hypochlorite  is  rapid,  evolution  of  oxygen  may  occur. 

The  reaction  taking  place  in  the  industrial  process  is  perhaps  best  interpreted  by  the 
equation  :  4C2H5  •  OH  +  16CaOCl2  =  3Ca(HC02)2  +  13CaCl2  +  8H20  +  2CHC13.  With 
acetone  the  reaction  would  be  as  follows,  trichloroacetone  being  formed  as  an  intermediate 
product :  2CH3  •  CO  •  CH3  +  6CaOCl2  =  Ca(C2H3O2)2  (calcium  acetate)  +  2CHCL  + 
3CaCl2  +  2Ca(OH)2. 

In  a  very  pure  form  for  pharmaceutical  use  it  is  obtained  by  treating  chloral  with  aqueous 
caustic  soda  solution,  sodium  formate  being  also  formed : 

/H 
CC13  •  C^     +  NaOH  =  CHC13  +  H  •  CO2Na. 

^O 

To  obtain  very  pure  chloroform  from  the  impure  product,  Anschiitz  treats  the  latter 
with  salicylic  anhydride,  C6H4CO2,  which  forms  a  crystalline  mass  only  with  chloroform, 
(C6H4CO2)4,  2CHC13;  this,  after  separation  from  the  mother-liquor,  is  heated  on  the  water- 
bath,  when  pure  chloroform  distils  off. 

Pictet  Chloroform  is  pure  chloroform  obtained  from  the  commercial  product  by 
freezing  it  at  —  80°  to  —  120°;  the  impurities  remain  in  the  liquid,  the  crystals  giving 
pure  chloroform. 

INDUSTRIAL  PREPARATION.  A  considerable  amount  of  chloroform  is  prepared 
even  to-day  from  chloride,  of  lime  and  alcohol,  but  the  latter  should  not  contain  fusel  oil. 

In  America,  F.  W.  Frericks  suggests  the  arrangement  shown  in  Fig.  104  for  the  manu- 
facture of  chloroform.  In  the  boiler  B  550  litres  of  94  per  cent,  alcohol  and  2550  litres  of 
water  (giving  20  per  cent.of  alcohol  in  the  mixture)  are  heated  by  a  steam  coil  to  60°  to  70°, 
a  fluid  paste  (free  from  lumps)  prepared  in  the  tank  A  (furnished  with  a  stirrer)  from  500 
kilos  of  chloride  of  lime  (35  per  cent,  of  available  chlorine)  and  about  1000  litres  of  water 
being  then  run  in  continuously  through  the  funnel  a  and  tube  b  to  the  bottom  of  B.  The 
reaction  is  instantaneous,  and  when  all  the  hypochlorite  has  been  added,  the  temperature 
is  maintained  at  60°  (B  being  jacketed)  until  the  whole  of  the  chloroform  is  distilled  off 
and  condensed  in  the  coil  C ;  the  distillation  is  followed  either  by  means  of  a  hydrometer 
under  the  bell-jar  e,  through  which  the  condensate  passes,  or  by  diluting*  sample  with  water : 

and  less  dangerous,  since  the  insensibility  extends  only  to  one  organ  or  one  region  of  the  subject 
of  the  operation. 

So  that,  to  chloroform,  ether,  etc.,  was  added,  in  1885,  cocaine,  which  paralyses  only  the  sensitive 
peripheral  nerves  without  influencing  the  motor  nerves.  By  studying  anaesthetic  and  hypnotic 
substances  chemists  were  able  to  determine  what  specific  atomic  groups  produced  anaesthetic 
properties  in  a  molecule.  Thus,  with  many  of  these  substances,  it  was  found  to  be  the  hydroxyl 
group  which  induced  sleep,  especially  when  it  is  united  to  carbon  joined  at  the  same  time  to  several 
alkyl  groups ;  replacement  of  the  hydroxyl  by  other  groups  resulted  in  the  disappearance  of 
the  anaesthetic  properties.  Also  various  amino-acid  groups,  under  certain  definite  conditions, 
give  rise  to  anaesthetics.  To  enumerate  all  the  members  of  the  vast  group  of  anaesthetics  which 
chemistry  has  placed  at  the  disposal  of  surgery  would  be  out  of  place  here,  but  the  following 
few  examples  may  be  mentioned  :  a-eucaine,  &-eucaine,  ortho/orm,  alipine,  holocaine,  and,  on 
the  other  hand,  sulphonal  (see  later),  trional,  dormiol,  hedonal,  veronal  (see  later),  etc.  Other 
properties  of  anaesthetics  are  described  in  Part  III,  in  the  section  on  Alkaloids. 


120 


ORGANIC    CHEMISTRY 


no  chloroform  should  separate.  The  chloroform  is  then  drawn  off  through  the  tap  d  and 
the  distillation  continued  at  a  temperature  above  60°,  the  alcohol  passing  over  being  col- 
lected in  D  and  then  passed  into  E ;  this  distillation  is  stopped  when  the  distillate  contains 
less  than  2  per  cent,  of  alcohol.  The  concentration  and  quantity  of  this  dilute  alcohol 
(about  1800  litres)  are  determined,  the  liquid  being  then  forced  through  the  tube  g  into  B, 
which  has  been  previously  emptied  through  h.  Further  alcohol  is  then  added  to  give  the 
amount  first  used,  and  a  second  operation  with  500  kilos  of  calcium  hypochlorite  carried  out. 
By  this  process  100  kilos  of  pure  chloroform  are  obtained  on  the  average  from  1022  kilos 
of  calcium  hypochlorite  (with  35  per  cent,  of  available  chlorine)  and  77  kilos  of  94  per  cent, 
alcohol,  whereas  with  the  proportions  of  reagents  formerly  in  use  as  much  as  100  kilos  of 
alcohol  and  1300  kilos  of  hypochlorite  were  consumed. 

In  recent  years  successful  use  has  been  made  of  the  method  of  making  chloroform  from 
acetone,  which  is  now  obtainable  cheap  and  very  pure  (quite  neutral  and  with  less  than 
0-05  per  cent,  of  aldehyde),  the  chloroform  thus  prepared  being  highly  pure.  Except  for 
the  reaction  vessel,  the  plant  is  similar  to  that  of  the  alcohol  process.  This  vessel  is  fur- 
nished, besides  with  a  jacket,  with  an  efficient  stirrer  and,  in  its  upper  part,  with  a  perforated 

or  gauze  disc  to  break  the  froth,  since  the 
reaction  is  at  first  rapid  and,  if  not  regulated, 
may  become  violent  and  dangerous.  To  the 
mixture  (free  from  lumps)  of  calcium  hypo- 
chlorite (250  kilos)  and  water  (800  litres), 
heated  to  50°  in  the  boiler,  is  slowly  (in 
about  an  hour)  added  28  litres  of  acetone, 
the  mass  being  cooled  to  prevent  the  tem- 
perature from  exceeding  55°  at  first,  and  60° 
at  the  end  of  the  addition.  The  condensed 
chloroform  of- sp.  gr.  1-5  is  collected,  while 
that  finally  distilling  over  with  sp.  gr.  1-45 
(by  heating  to  85°)  is  set  apart  for  the 
succeeding  operation,  as  it  contains  a  little 
acetone.  The  crude  chloroform  obtained  is 
washed  with  a  little  water  and  sodium 
carbonate,  then  stirred  with  one-third  of  its 
FIG.  104.  volume  of  water  and  decanted  from  the 

latter,  and  afterwards  washed  two  or  three 

times,  in  a  lead-lined  vessel  fitted  with  a  stirrer,  with  a  little  66°  Be.  sulphuric  acid 
until  the  acid  is  no  longer  turned  brown.  After  the  acid  has  been  thoroughly  removed 
from  the  chloroform,  this  is  washed  with  water,  dried  over  CaCl2,  and  distilled  from  a  copper 
still.  The  washing  with  water  and  the  drying  may  be  omitted,  the  chloroform  being  then 
distilled  with  a  little  soda  to  neutralise  traces  of  acid  and  the  first  and  last  portions  of  the 
distillate  kept  separate.  The  bulk  of  the  chloroform  distilled  is  highly  pure  and  the  yield 
is  205  kilos  of  a  crude  product  from  100  kilos  of  acetone  and  1110  kilos  of  hypochlorite 
(about  34  per  cent,  of  active  Cl) ;  175  kilos  of  pure  chloroform  1  are  obtained. 

1  TESTS  FOR  CHLOROFORM.  Minute  quantities  of  chloroform  may  be  detected  by 
heating  a  little  of  the  liquid  gently  with  a  few  drops  of  aniline  and  of  alcoholic  potash  solution, 
the  characteristic  repulsive  odour  of  phenylcarbylamine  (phenyl  isocyanide)  being  formed.  Pure 
chloroform  for  medicinal  use  should  not  be  acid  or  give  a  precipitate  with  silver  nitrate  solution 
or  redden  potassium  iodide  solution ;  on  evaporation  it  should  not  leave  a  residue  of  water  or 
odorous  substances,  and  it  should  not  darken  with  concentrated  sulphuric  acid.  To  test  for 
the  presence  in  it  of  carbon  tetrachloride,  20  c.c.  are  treated  with  a  solution  of  3  drops  of  aniline 
in  5  c.c.  of  benzene ;  turbidity  or  separation  of  crystals  of  phenylurea  indicates  with  certainty 
the  presence  of  the  tetrachloride.  To  ascertain  if  it  contains  alcohol  it  is  treated  with  a  very  dilute 
potassium  permanganate  solution,  which  is  decolorised  in  presence  of  this  impurity. 

Its  estimation  is  effected  by  treating  a  given  weight  with  Fehling's  solution  (see  under  Sugar 
Analysis )  and  heating  the  mixture  in  a  closed  bottle  on  a  water-bath  for  some  hours  (until  the 
odour  of  chloroform  disappears ),  the  cuprous  oxide,  formed  according  to  the  equation,  CHC13  + 
2CuO  +  5KOH  =  K2C03  +  3H20  +  3KC1  +  Cu20,  being  weighed.  One  molecule  of  chloro- 
form corresponds  with  2  atoms  of  copper. 

It  may  be  determined  also  by  heating  with  alcoholic  potash  in  a  reflux  apparatus  on  the  water- 
bath  ;  it  is  then  diluted  with  water,  the  alcohol  distilled  off,  and  the  potassium  chloride  formed 
(together  with  potassium  formate,  see  preceding  page)  titrated  with  a  standard  silver  nitrate 
solution,  This  method  serves  for  the  estimation  of  all  alkyl-hcdogen  compounds. 


IODOFORM  121 

During  recent  years  the  industrial  preparation  of  chloroform  has  again  been  attempted 
by  electrolysing  an  aqueous  solution  of  KC1  (20  per  cent.)  into  which  alcohol  or  acetone 
is  slowly  introduced ;  if  the  temperature  is  kept  at  about  60°,  the  chloroform  distils  off  as 
it  is  formed.  In  this  process  1  h.p.-hour  is  consumed  to  produce  40  grams  of  chloroform 
(L.  Zambelleti,  1899). 

According  to  the  Besson  process  (Ger.  Pat.  129,237),  continuous  production  and  a  good 
yield  are  obtained  by  heating,  in  a  vessel  divided  into  cells  communicating  below,  alcohol 
previously  chlorinated  to  the  sp.  gr.  35°  Be.  with  chloride  of  lime  and  alkali  in  the  hot. 

Attempts  have  been  made  to  prepare  chloroform  industrially  by  reducing  carbon 
tetrachloride  in  the  hot  with  nascent  hydrogen :  CC14  +  H2  =  HC1  +  CHC13,  but  the 
product  is  contaminated  with  CC14  and  CS2  (used  in  making  the  CC14)  which  are  eliminated 
with  difficulty. 

Erlworthy  and  Lange  (Fr.  Pat.  354,291,  1905)  propose  to  produce  chloroform  from 
methane  and  chlorine  diluted  with  indifferent  gases  (N,  CO2)  by  subjecting  the  mixture 
to  the  action  of  light  in  suitable  retorts  :  CH4  +  6C1  =  3HC1  +  CHC13,  but  the  process 
has  apparently  not  been  applied  in  practice,  although  in  1913  improved  results  were  obtained 
with  ultra-violet  rays. 

The  pre-war  price  of  industrial  chloroform  was  about  £8  per  100  kilos ;  redistilled  cost 
2s.  lOd.  per  kilo;  the  pharmacopoeial  preparation  2s.  2d.;  puriss.  from  chloral,  6s.  5d.  to 
9s.  Id. ;  Pictet's,  12s.  per  kilo,  and  that  of  Anschiitz  IQd.  per  50  grams.  Part  of  the 
chloroform  consumed  in  Italy  is  imported  from  abroad,  the  Italian  output  prior  to  the  war 
being  about  10  tons  per  annum. 

In  1909  Germany  exported  150  tons  of  chloroform,  while  Great  Britain  imported 
16  cwt.  and  exported  14  cwt.  in  1910.  The  United  States  imported  8  cwt.  in  1910. 

IODOFORM  (Tri-iodomethane),  CHI3,  was  discovered  by  Serullas  in  1822, 
and  its  constitution  was  established  by  Dumas  who,  unlike  his  predecessors, 
did  not  overlook  the  very  small  proportion  of  hydrogen  (0'25  per  cent.)  present. 

It  is  formed  by  heating  ethyl  alcohol  or  acetone  with  iodine  and  sufficient 
alkali  hydroxide  or  carbonate  to  decolorise  the  iodine  (Lieben's  reaction)  : 
C2H5OH  +  81  +  6KOH  =  CHI3  +  H  •  COOK  -f  5KI  +  5H2O. 

This  reaction  (separation  of  yellow  crystals  and  formation  of  a  character- 
istic odour)  is  so  sensitive  that  it  serves  for  the  detection  of 'minute  traces 
(1  :  2000)  of  ethyl  alcohol  or  acetone  in  other  liquids  (waiting  twelve  hours 
for  the  separation  of  crystals  if  the  amount  of  alcohol  is  small);  the  same 
reaction  is,  however,  given  by  isopropyl  alcohol,  acetaldehyde  (and  by  almost 
all  compounds  containing  the  group  CH3  •  CO  •),  but  not  by  methyl  alcohol, 
ether,  or  acetic  acid. 

For  the  practical  preparation  of  iodoform  32  parts  of  K2C03  are  dissolved  in  80  parts 
of  water  and  16  parts  of  alcohol,  the  mixture  being  heated  to  70°  and  32  parts  of  iodine 
gradually  added.  The  separated  iodoform  is  filtered  off  and  the  iodine  of  the  potassium 
iodide  in  the  filtrate  utilised  as  follows  :  20  parts  of  HC1  are  added  and  2  to  3  parts  of 
potassium  dichromate,  the  liquid  being  then  neutralised  with  K2CO3,  mixed  with  a  further 
32  parts  of  K2CO3,  16  parts  of  alcohol  and  6  parts  of  iodine.  On  heating,  a  second  quantity 
of  iodoform  separates,  and  after  this  or  another  similar  operation  the  mother-liquor  is 
treated  to  recover  the  iodine  from  the  potassium  iodide. 

It  has  been  proposed  to  prepare  iodoform  by  treating  the  metallic  acetylides  (see  p.  110) 
wifch  iodine  and  caustic  soda. 

It  seems  that  practical  use  is  now  made  of  the  electrolytic  process,  using  a  bath  of 
6  parts  KI,  2  parts  soda,  8  vols.  alcohol,  and  40  of  water  at  60°  to  65°.  The  iodine  to  be 
used  in  the  reaction  is  set  free  at  the  anode,  and  to  avoid  the  formation  of  a  little  iodate 
with  the  KOH  formed  at  the  cathode  the  latter  is  enclosed  in  parchment  paper. 

When  pure,  iodoform  crystallises  in  hexagonal,  yellow  plates  (sp.  gr.  2), 
insoluble  in  water  but  soluble  in  alcohol  or  ether.  It  has  a  penetrating  and 
persistent  odour,  recalling  partly  that  of  saffron  and  partly  that  of  phenol. 
It  melts  at  119°,  readily  sublimes,  and  is  volatile  in  steam.  When  heated  with 
either  alcohol  or  reducing" agents,  it  gives  methylene  iodide, 


122 


ORGANIC    CHEMISTRY 


It  is  used  in  surgery  as  an  important  antiseptic,  which,  however,  acts 
indirectly  on  bacteria  by  means  of  the  decomposition  products  formed  from 
it  under  the  action  of  the  pus  of  wounds  or  of  the  heat  of  the  body. 

TESTS  FOR  IODOFORM.  It  should  leave  no  residue  on  sublimation  and  should 
dissolve  completely  in  alcohol  or  ether.  It  is  estimated  by  heating  about  1  gram  with 
about  2  grams  of  silver  nitrate  and  25  c.c.  of  concentrated  nitric  acid  (free  from  chlorine) 
in  a  reflux  apparatus  so  that  the  liquid  does  not  boil;  when  the  nitrous  vapours  have 
disappeared  the  liquid  is  diluted  with  water  to  150  c.c.  and  heated,  the  silver  iodide  being 
collected  on  a  tared  filter,  dried  and  weighed  :  1-789  grams  Agl  corresponds  with  1  gram 
iodoform. 

Owing  to  its  disagreeable  odour,  it  has  been  to  some  extent  replaced  latterly 
by  Xeroform,  which  is  a  tribromophenoxide  of  bismuth,  C6H2Br3O  •  OH,  Bi2O2, 
obtained  by  the  action  of  bismuth  chloride  on  sodium  tribromophenoxide,  and 
forming  a  tasteless,  odourless,  yellow  powder  insoluble  in  water  or  alcohol; 
it  is  used  also  as  a  disinfectant  for  the  intestines,  and  costs  44s.  to  48s.  per 
kilo,  whilst  iodoform  costs  only  24s.  to  28s.  a  kilo. 

CARBON  TETRACHLORIDE  (Tetrachloromethane),  CC14  (see  Vol.  I.,  p.  470). 

POLYCHLORO-DERIVATIVES    OF    ETHYLENE    AND    ETHANE.1     Asymm. 

1  Since  1908  (Ger.  Pats.  196,324,  204,516,  204,883,  etc.),  the  Chemische  Fabrik  Griesheim- 
Elektron  of  Frankfort,  and  the  Usines  electriques  de  la  Lonza  of  Geneva  have  placed  on  the 
market,  as  non-inflammable  solvents  for  industrial  purposes,  six  chlorinated  compounds  obtained 
as  colourless  liquids  by  the  action  of  chlorine  on  acetylene.  They  are  all  good  solvents  for  fats, 
resins,  rubber,  bitumen,  sulphur,  etc.,  and  can  replace  advantageously  benzine,  carbon  disulphide, 
and  alcohol,  since  they  are  not  inflammable  and  their  vapours  do  not  form  explosive  mixtures 
with  air;  over  carbon  tetrachloride  they  have  the  advantage  of  not  attacking  the  metal  parts 
of  the  extraction  apparatus,  and  the  loss  on  extraction  varies  from  0-3  to  0-8  per  cent.;  they 
are,  however,  dearer  than  the  ordinary  solvents  and  seem  to  be  injurious  to  health.  Acetylene 
tetrachloride  (tetrachloroethane)  was  prepared  in  1903  by  the  Consortium  fur  elektrochemische 
Industrie  of  Nuremberg  (Ger.  Pat.  154,657)  by  the  interaction  of  acetylene  and  chlorine  in 
presence  of  antimony  chloride  as  catalyst.  Dichloroethylene,  used  in  the  manufacture  of  thio- 
indigo,  is  formed  quantitatively  from  tetrachloroethane  by  the  action  of  ordinary  metals  in  the 
hot  in  presence  of  a  little  water  (Ger.  Pat.  217,554).  Trichloroethylene  is  obtained  from  tetra- 
chloroethane by  heating  it  with  lime  (Ger.  Pat.  170,900 ) ;  by  treatment  of  the  products  gradually 
forming  with  lime  and  chlorine  alternately,  C2HC15,  C2C14  and  C2C16  (solid)  may  be  prepared. 

With  trichloroethylene  various  organic  syntheses  may  be  effected.  Thus,  with  sodium 
ethoxide  it  yields  dichlorovinyl  ether,  C2HC12  •  OC2H5 ;  this,  in  its  turn,  exhibits  marked  reactivity, 
and  on  addition  of  Cl  or  HC1  gives  saturated  products  which,  on  distillation,  liberate  ethyl  chloride 
and  form  mono-  and  di-chloroacetyl  chlorides,  C2H2C120  and  C2HC130.  With  water  in  presence  of 
a  trace  of  HC1  (as  catalyst)  at  the  ordinary  temperature,  dichlorovinyl  ether  gives  quantitatively 
ethyl  chloroacetate,  CH2C1  •  COOC2H5  (Ger.  Pats.  210,502  and  216,716),  which  was  first  obtained 
from  acetic  acid  and  is  now  more  economically  derived  from  acetylene ;  it  is  used  in  numerous 
important  syntheses,  including  that  of  indigo. 

The  properties  of  these  compounds  are  given  in  the  following  Table  : 


DICHLORO- 
ETHYLENE 

TRICHLORO- 
ETHYLENE 

TETRA- 

CHLORO- 
ETHYLENE 

TETRA- 
CHLORO- 
ETHANE 

PENTA- 

CHLORO- 
ETHANE 

HEXA- 

CHLORO- 
ETHANE 

C2H2Cl2 

C2HC13 

C2C14 

C2H2CI4 

C2HC15 

C2C16 

Common  name   . 

Dieline 

Trieline 

Etiline 

Tetraline 

Pentaline 

—        • 

Specific  gravity  . 

1-278  (1-25) 

1-471 

1-628 

1-600 

1-685  (1-70) 

2 

Boiling-point 

52°  (55) 

85°  (88) 

119°  (121) 

144°  (147) 

159° 

(185°) 

Vapour  pressure  at  20° 

205  mm. 

56 

17 

11 

7 

3 

Specific  heat  at  20° 

0-270 

0-223 

0-216 

0-268 

0-266 



Heat  of  evaporation 

41  cals. 

57-8 

50 

52-8 

45 

.  

Freezing-point    . 

— 

-  73° 

-  19° 

—  36° 

-  22° 

— 

Uses  and  properties     . 

Keadily  dis- 

Dissolves fats, 

Serves   well 

Dissolves  re- 

Keadily dis- 

Has      an 

solves       rub- 

paraffin   wax 

for       remov- 

sins and  var- 

solves    cellu- 

odour       like 

ber 

and    vaseline 

ing  spots 

nishes,      like 

lose      acetate 

camphor, 

better      than 

turpentine 

for     artificial 

and       serves 

benzine 

and      alcohol 

silk      and 

as    an    insec- 

Ger. Pats.  201,705 
204,516 
216,070 

Ger.  Pats. 
171,900 
206,854 

and   dissolves 
cellulose   ace- 
tate for  films 
and    artificial 

cinemato- 
graph  films 

ticide 

254,068 

silk 

Trichloroethylene,  C2HC13,  is  used  also  as  a  non-inflammable  solvent  in  chemical  cleaning 
works,  in  the  manufacture  of  oils  and  fats,  in  making  lacs,  and  in  one  of  the  syntheses  of  indigo  : 
with  sodium  ethoxide  it  gives  dichlorovinyl  ether,  which  with  water  yields  ethyl  chloroacetate, 


ALCOHOLS  123 

HEPTACHLOROPROPANE  was  prepared  in  1910  by  Boeseken  and  Prins  from  tetra- 
chloroethylene  and  chloroform  in  presence  of  aluminium  chloride  as  catalyst. 

II.  HALOGENATED  DERIVATIVES  OF  UNSATURATED 
HYDROCARBONS 

These  are  obtained  from  saturated  halogen  derivatives  by  partial  elimination  of  the 
halogen  hydracid :  C2H4Br2  =  HBr  +  C2H3Br.  They  are  formed  also  by  incomplete 
saturation,  with  halogens  or  halogen  hydracids,  of  the  less  saturated  hydrocarbons  : 
C2H2  +  HBr  =  C2H3Br  (see  Table  in  footnote). 

Bromoacetylene,  CH  j  CBr,  is  a  gas  liquefying  at  —  2°  and  ignites  spontaneously  in  the 
air.  It  gives  brilliant  luminescent  effects,  even  if  mixed  with  air.  It  ozonises  atmospheric 
oxygen,  but  the  latter  is  not  ionised,  as  is  the  case  with  phosphorus. 

The  allyl  compounds,  C3H5X,  are  formed  from  allyl  alcohol  by  the  action  either  of 
halogen  hydracid  or  of  phosphorus  and  halogen. 

ALLYL  CHLORIDE  (Chloro-3-propene-i),  CH2  :  CH  •  CH2C1;  the  bromide  and  iodide 
have  analogous  constitutions.  These  are  related  to  the  natural  allyl  compounds  (garlic 
oil  and  mustard  oil).  Two  stereoisomerides  are  known : 

H— C— Cl  H— C— Cl 

a-chloropropylene.  and  iso-a-chloropropylene,         \\ 

H — C — CH.j  CHg — C — H 

TETRABROMOETHANE,  CHBr2  •  CHBr2  (improperly  termed  acetylene  bromide)  is 
prepared  industrially  in  the  impure  state  bypassing  bromine  in  at  the  top  of  a  cooled  earthen- 
ware  coil  and  acetylene  in  at  the  bottom,  the  liquid  product  collecting  at  the  bottom :  C2H2 
+  2Br2  =  C2H2Br4  +  64  cals.  It  boils  at  215°  with  partial  decomposition  and  does  not 
solidify  at  —  20°.  It  contains  92-5  per  cent,  of  bromine  and  has  a  high  specific  gravity 
(2-943),  and  on  this  account  is  used  for  the  mechanical  separation  of  mineral  components; 
thus  large  quantities  are  employed  to  separate  diamonds  (sp.  gr.  3-35)  from  the  sands  of 
Western  Africa  (sp.  gr.  2-4).  It  is  despatched  in  vessels  similar  to  those  used  for  bromine. 
It  is  obtained  pure  by  treatment  with  alcohol  and  zinc  dust,  which  converts  it  into 
dibromoacetylene ;  the  latter  is  then  purified  by  distillation  and  transformed  into  the 
tetrabromo-cqmpound  by  means  of  bromine. 

CC.    ALCOHOLS 

These  form  an  important  group  of  organic  compounds  containing  one  or 
more  characteristic  hydroxyls,  the  hydrogen  of  which  has  pronounced  reactive 
properties,  so  that  numerous  series  of  other  compounds  are  derived  from  the 
alcohols.  They  have  a  neutral  reaction,  although  their  chemical  behaviour 
is  analogous  to  that  of  the  inorganic  bases  which  always  contain  the  anion 
OH'.  The  majority  of  these  alcohols  are  colourless  liquids,  but  those  of 
high  molecular  weights  are  oily,  solid,  and  sometimes  yellowish.  The  first 
members  of  the  series  are  soluble  in  water,  but  with  increase  of  molecular 
weight  the  solubility  decreases  and  the  smell,  generally  slight,  also  tends  to 
disappear.  They  are  often  found  in  nature  either  free  or  combined  with 
organic  acids,  in  the  fats,  waxes,  fruits,  essential  oils,  etc. 

According  to  the  number  of  hydroxyl  groups  they  contain,  they  are  divided 
into  mono-,  di-,  .  ,  .  polyhydric  alcohols,  and  may  belong  either  to  the  saturated 
or  to  the  unsaturated  series — already ,  studied  in  connection  with  the  hydro- 
carbons— of  which  they  retain  the  fundamental  characters;  added  to  the 
latter  are  those  characteristic  of  the  alcoholic  group,  which  we  shall  study 
generally  with  the  monohydric  alcohols. 

and  this,  with  aniline  in  presence  of  calcium  carbonate,  forms  the  ethyl  ester  of  phenylglycine ; 
with  potassium  carbonate  the  latter  gives  the  corresponding  potassium  salt,  which  gives  rise  to 
indigo  on  condensation  with  calcium  silicide  (see  Vol.  I.,  p.  500). 

The  existence  of  cis-  and  trans-stereoisomerides  of  symmetrical  diMoroethylene,  CHC1  :  CHC1, 
appears  proved. 


124  ORGANIC    CHEMISTRY 

I.  SATURATED   MONOHYDRIC   ALCOHOLS 

The  specific  gravity  of  these  is  always  lower  than  that  of  water,  and  up  to 
the  C16  member  they  distil  unchanged  at  the  ordinary  pressure  ;  beyond  that 
reduced  pressure  must  be  employed. 

That  alcohols  always  contain  a  hydroxyl  group,  OH,  may  be  shown  by  the  following 
chemical  reactions  : 

The  alcohols  may  be  obtained  by  the  action  of  silver  hydroxide,  Ag  •  OH  (which 
certainly  contains  the  group  OH),  or  even  of  the  alkalis  or  hot  water,  on  halogenated 
hydrocarbons  :  CBH2n  +  XI  +  AgOH  =  Agl  -f  CnH2  +  nlOH. 

With  the  halogen  hydracids  the  hydroxyl  separates  from  the  alcohols  in  the  form  of 
water:  CnH2n+1OH  +  HBr  —  H2O  +  CBH2n  +  1Br  ;  the  same  happens  with  oxyacids, 
the  so-called  esters  being  formed:  CnH2n+1OH  +  HN03  =  H2O  +  CBH2B+1N03.  Just 
as  sodium  and  potassium  react  with  water,  liberating  hydrogen,  so  do  they  act  on  the 
alcohols,  from  which  only  the  typical  hydrogen  (hydro  xylic),  not  united  directly  to  carbon, 
is  eliminated:  CBH2B+1OH  +  Na  =  CBH2n+  ^Na  (sodium  alkozide)  +  H.  Magnesium 
alkoxides  are  also  easily  obtained.  With  phosphorus  trichloride,  however,  the  hydroxyl 
group  is  eliminated  : 


PC13  =  3CyB^  +  1Cl  +  P(OH)3. 

On  p.  17  the  difference  in  constitution  between  ethyl  alcohol  and  methyl  ether  has 
been  demonstrated. 

If  thex  hydroxyl  group  occurs  in  place  of  a  hydrogen  atom  in  the  methyl  group  (—  CH3) 
at  the  extremity  of  the  hydrocarbon  chain,  the  primary  alcohols  are  obtained,  all  con- 


taining   the   characteristic  group  —  CH2  •  OH     i.  e.,  —  Of  ),   e.  g.,  propyl  alcohol, 

\OH  •' 
CH3  •  CH2  •  CH2  •  OH,  and  by  oxidation  of  these  alcohols  are  formed  first  aldehydes  with 


/         X 
the  characteristic  group  I  X. — Cf^      j,  and  then  acids  with  the  characteristic  carboxyl 

group  — COOH  (  i.  e.,  • — C'f         ].     Substitution  of  a  hydroxyl  for  a  hydrogen  atom  in  an 

\OH 

intermediate  methylene  group  (  —  CH2)  in  the  saturated  hydrocarbon  chain  yields  secondary 

(TT        \ 
i.  e.^C-^p-Ti )  and  on  oxidation 

give  ketones  containing  the  special  group  ]>CO.  Finally  the  substitution  of  the  hydrogen 
of  a  branched  hydrocarbon  may  take  place  in  the  methinic  group  (=CH),  giving  tertiary 
alcohols  with  the  characteristic  grouping  =C  •  OH,  the  other  three  valencies  of  the  carbon 
being  united  to  three  carbon  atoms.  When  the  secondary  alcohols  are  oxidised  they 
cannot  give  either  acids  or  ketones  with  an  equal  number  of  carbon  atoms,  but,  if  the 
oxidation  is  energetic,  the  chain  breaks,  and  then  acids  and  ketones  may  be  formed,  but 
with  less  numbers  of  carbon  atoms. 

According  to  B.  Neave  (1909),  primary,  secondary,  and  tertiary  alcohols 
may  be  distinguished  by  the  Sabatier  and  Senderens  reaction  (see  p.  35),  by 
passing  the  vapour  of  the  alcohol  over  finely  divided  copper  heated  at  300° : 
the  primary  alcohols  form  hydrogen  and  aldehydes  (recognisable  by  Schiff's 
reaction;  see  section  on  Aldehydes),  the  secondary  ones  give  hydrogen  and 
ketones  (detectable  by  semicarbazide  hydrochloride  solution)  and  the  tertiary 
alcohols  give  water  and  unsaturated  hydrocarbons  (which  decolorise  bromine 
water). 

The  primary  alcohols  and  the  corresponding  ethers  have  the  highest  boiling- 
points,  the  tertiary  ones  and,  in  general,  those  with  branched  chains  showing 
the  lowest  boiling-points. 

In  the  group  of  alcohols  the  isomerism  and  the  number  of  isomerides  are 


FORMATION    OF    ALCOHOLS  125 

similar  to  those  of  the  halogenated  derivatives  of  the  hydrocarbons,  since  the 
halogen  atom  is  here  replaced  by  a  hydroxyl  group. 

The  names  of  the  primary  alcohols  are  made  from  those  of  the  corresponding  hydro- 
carbons (see  p.  30),  with  the  termination  ol,  and  those  of  the  secondary  and  tertiary  alcohols 
are  derived  from  the  names  of  the  hydrocarbons  with  the  longest  non-  branched  chains; 
or  the  secondarjfcfjid  tertiary  alcohols  may  be  regarded  as  derivatives  of  methyl  alcohol 
or  carbinol,  CH3  •  JH,  formed  by  substitution  of  the  hydrogen  atoms  of  the  methyl  group. 
We  have,  hence,  two  different,  but  still  equally  clear,  systems  of  nomenclature.  For 
example  : 

(1)  Normal  butyl  alcohol  :  CH3  •  CH2  •  CH2  •  CH2  •  OH  =  butan-1-ol  or  n-propylcarbinol. 

2          l 

(2)  Secondary  butyl  alcolwl  :   CH3  •  CH2  •  CH(OH)  •  CH3  =  butan-2-ol  or  methylethyl- 
carbinol.  • 

123 

(3)  Isobulyl  alcohol  :  CH3  •  CH  •  CH2  •  OH  =  2-methylpropan-3-ol  or  isopropylcarbinol. 


3 

1  23 


CH3 

(4)  Tertiary  butyl  alcohol :  CH3^-C — CH3  =  2-methylpropan-2-ol  or  trimethylcarbinol. 

/\ 
CH3     OH 

PROCESSES  OF  FORMATION  OF  MONOHYDRIC  ALCOHOLS.  As  well 
as  from  the  halogen  derivatives,  the  alcohols  may  usually  be  obtained  by 
decomposing  esters  with  acids,  alkalis,  or  superheated  water.  This  reaction 
is  termed  saponification  or  hydrolysis  : 

C2H5O  •  NO2  +  KOH  =  KNO3  +  C2H5  •  OH. 

In  a  general  way,  the  primary  alcohols  are  formed  by  reducing  the  acids 
(CnH2nO2)  or  aldehydes  (CnH2nO)  with  nascent  hydrogen  : 

CH3  •  C<f     (acetaldehyde)  +  2H  =  CH3  •  CH2  •  OH. 
XH 

Since  the  acids,  in  their  turn,  may  be  prepared  from  the  alcohols  with  one 
carbon  atom  less,  we  have  at  our  disposal  a  general  reaction  for  preparing 
synthetically  any  higher  alcohol. 

The  secondary  alcohols  are  formed  by  reducing  the  ketones,  CnH2nO,  e.  g.  : 

CH3  •  CO  •  CH3  +  H2      =      CH3  •  CH(OH)  •  CH3 

Acetone  Isopropyl  alcohol 

(see  later,  Aldehydes  and  Ketones). 

The  tertiary  alcohols  are  formed  by  the  prolonged  action  of  zinc  methyl 
on  acid  chlorides,  the  intermediate  compounds  thus  formed  being  decomposed 
with  water  r 

For  the  secondary  and  tertiary  alcohols  Grignard's  reaction  may  also  be 
employed  (see  later,  Alkylmetallic  Compounds). 

Of  more  industrial  importance,  however,  is  the  preparation  of  some  of  the 
more  common  of  these  alcohols  by  the  distillation  of  wood  or  the  fermentation 
of  certain  carbohydrates  (see  later}. 

In  addition  to  the  properties  of  the  alcohols  given  above,  namely,  their 
behaviour  towards  acids,  halogens  (which  oxidise  them),  chlorides,  and  oxidising 
agents  in  general  (which  give  aldehydes  and  acids),  it  may  be  mentioned  that 
the  higher  alcohols  (primary)  are  transformed  into  the  corresponding  acids 
by  simple  heating  with  soda  lime.  Traces  of  primary  alcohols  are  detectable 
by  oxidising  with  permanganate  and  sulphuric  acid  and  then  testing  for 
aldehyde,  which  reddens  a  sulphurous  acid  solution  of  fuchsine. 


126 


ORGANIC    CHEMISTRY 


PHYSICAL  CONSTANTS  OF  THE  MONOHYDRIC  ALCOHOLS 


Name  and  Formula 

Specific 
gravity 

Melting- 
point 

Boiling- 
Point 

1.     Methyl  alcohol,  CH3-OH 

0-812  (0°) 

-94°,  -98° 

66° 

2.     Ethyl  alcohol,  C2H5-OH 

0-806 

-112°,  -117° 

78° 

3a.  Normal  propyl  alcohol  (prim.  ) 

CH3-CH2-CH2-OH 

0-817 

-127° 

97° 

36.  Isopropyl  alcohol  (sec.  ) 

CH3-CH(OH)-CH3 

0-789  (20°) 

— 

81° 

4a.  Normal  butyl  alcohol  (prim.),  C4H9-OH. 

0-810 

-80°(-122°) 

117° 

46.  Normal  butyl  alcohol  (sec.),  C4H9-OH    . 

0-808 

— 

100° 

4c.  Iso  butyl  alcohol,  C4H9-OH 

0-806  (20°) 

— 

107° 

4:d.  Tertiary  butyl  alcohol  (trimethylcarbinol  ) 

C4H9-OH 

0-786  (20°) 

+  25° 

83° 

5a.  Normal  amyl  alcohol  (prim.  ) 

CH3-[CH2]3-CH2-OH 

0-817  (20°) 

— 

138° 

56.  Amyl  alcohol  of  fermentation  or  isobutyl- 

carbinol,  (CH3)2:CH-CH2-CH2-OH 

0-810  (20°) 

— 

130°    - 

5c.  Active  amyl  alcohol  or  sec.  butylcar  binol, 

CH3-CH(C2H5)-CH2-OH 

0-816  (20°) 

— 

128° 

5d.  Trimethyl-  or  tertiary  butyl-  car  binol, 

(CH3)3C-CH2-OH 

0-812  (20°) 

49° 

113° 

5e.  Diethylcarbinol,  C2H5-CH(OH)-C2H5      . 

0-831  (0°) 

— 

117° 

5/.  Methylpropylcarbinol, 

CH3-[CH2]2-CH(OH)-CH3 

0-824  (0°) 

— 

119° 

5g.  Methylisopropylcar  binol, 

(CH3)2CH-CH(OH)-CH3 

0-819  (0°) 

— 

112-5° 

5/t.  Dimethylethylcarbinol, 

(CH3)2C(OH)-C2H5 

0-814  (15°) 

—  12° 

102° 

6.     Normal  hexyl  alcohol  (prim.  ),  C6H13-OH  . 

0-833  (0°) 

— 

157° 

7.     Normal  heptyl  alcohol  (prim.),  C7H15-OH 

0-836 

— 

175° 

8.     Normal  octyl  alcohol  (prim.  ),  C8H17-OH 

0-839 

— 

191° 

9.     Normal  nonyl  alcohol,  C9HJ9-OH 

0-842 

-5° 

213° 

10.     Decyl  alcohol,  C10H21-OH     . 

0-839 

+  7° 

231° 

11.     Undecyl  alcohol,  CnH^-OH. 

— 

+  19° 

131°(15mm.) 

12.    Dodecyl  alcohol,  C^H^-OH 

0-831 

24° 

143°      „ 

13.     Tridecyl  alcohol,  C13H27-OH. 

— 

30-5° 

156°       „ 

14.     Tetradecyl  alcohol,  C14H29-OH 

0-824 

38° 

167°      „ 

15.     Pentadecyl  alcohol,  C15H31-OH      . 

— 

45-46° 

— 

16.     Hexadecyl  (cetyl)  alcohol,  C^H^-OH    . 

0-818 

50° 

190°       „ 

17.     Octodecyl  alcohol,  C18H37-OH 

0-813 

59° 

211° 

18.     Ceryl  alcohol,  C26H53-OH      . 

— 

79° 

— 

19.     Myricyl  alcohol,  C30H61-OH  . 

— 

85° 

— 

By  the  behaviour  of  the  nitre-compounds  (prepared  from  the  corresponding 
iodides  and  silver  nitrite)  and  also  by  the  initial  velocity  and  degree  of  esterifica- 
tion,  primary  alcohols  may  be  differentiated  from  the  secondary  and  tertiary 
ones. 

Various  primary  normal  alcohols  enter  inorganic  compounds  as  alcohol  of 
crystallisation,  e.  g.,  BaO,  2CH3  •  OH;  CaCl2,  4CH3  •  OH;  KOH,  2C2H5  •  OH; 
MgCl2,  6C2H5  •  OH ;  CaCl2,  4C2H5  •  OH,  etc. ;  it  is  hence  evident  why  calcium 
chloride  cannot  be  used  for  drying  alcohol,  although  it  serves  well  in  the  case 
of  ether. 


METHYL    ALCOHOL 


127 


METHYL  ALCOHOL,   CH3  .  OH    (Methanol  or  Carbinol) 

This  is  also  called  wood-spirit,  since  it  was  obtained  by  Boyle  in  1661 
from  wood-tar,  and  is  to-day  prepared  in  large  quantities  by  distilling  wood. 
Its  chemical  composition  was  not  determined  until  1834  (by  Dumas  and 
Peligot). 

In  nature  it  occurs  in  the  form  of  its  salicylic  ester,  in  Gaultheria  pro- 
cunibens  (in  Canada)  and  as  butyric  ester  in  the  bitter  seeds  of  Heracleum 
giganteum. 

PROPERTIES.  When  pure  it  is  a  colourless  liquid,  b.-pt.  66°,  with  a 
faint  alcoholic  smell;  it  burns  with  a  non-luminous  flame,  solidifies  at  very 
low  temperatures,  and  melts  at  —  94°.  When  1  kilo  is  burned,  5310  cals. 
are  developed,  and  its  heat  of  evaporation  is  262'2  cals.  Its  vapour  pressure 
at  different  temperatures  is  as  follows  (mm.  of  mercury). 


Temperature 
Pressure 


-10° 
15-5 


0° 
29-6 


20° 
96 


30° 
160 


40° 
260 


50° 
406 


60°         80°         100° 
625      1341        2621 


It  dissolves  in  all  proportions  in  water,  alcohol,  ether,  or  chloroform.  Its 
specific  gravity  at  15°  is  0'7984  (at  64*8°,  0'7476),  and  in  aqueous  solution 
the  amount  of  the  alcohol  present  may  be  determined  from  the  specific 
gravity. * 

Like  spirits  of  wine  (ethyl  alcohol)  it  is  intoxicating,  dissolves  fats,  oils,  etc., 
and  even  when  anhydrous  it  dissolves  calcined  copper  sulphate,  forming  a" 
bluish-green  solution. 

Methyl  alcohol  is  less  poisonous  than  higher  alcohols,  but  in  the  animal, 
especially  in  the  human  organism,  it  undergoes  transformations  which  render 
it  far  more  injurious  than  ethyl  alcohol.  The  latter  is  subjected  to  rapid 
combustion  in  the  organism,  whereas  methyl  alcohol  is  slowly  oxidised  with 
formation  of  formic  acid,  this  behaving  quite  differently  from  all  other  organic 
acids  owing  to  its  aldehydic  character. 

The  process  of  oxidation  of  methyl  alcohol  varies  in  organisms  of  different 
species,  and  perhaps  in  different  individuals  of  the  same  species,  and  since 
methyl  alcohol  is  absorbed  especially  by  definite  nerve  elements,  it  is  in  these 
that  the  slow  oxidation  occurs,  causing  serious  disturbances  and  consequences 


Per 

Per 

Per 

Per 

Per 

Specific 

cent,  by 

Specific 

cent,  by 

Specific 

cent,  by 

Specific 

cent,  by 

Specific 

cent,  by 

gravity 

weight 

gravity 

weight 

gravity 

weight 

gravity 

weight 

gravity 

weight 

at  15-56° 

of  the 

at  15'56° 

of  the 

at  15-56° 

of  the 

at  15-56 

of  the 

at  15-56° 

of  the 

alcohol 

alcohol 

alcohol 

alcohol 

alcohol 

0-99729 

1 

0-96524 

22 

0-93335 

42 

0-89358 

62 

0-84521 

82 

0-99554 

2 

0-96238 

24 

0-92975 

44 

0-88905 

64 

0-84001 

84 

0-99214 

4 

0-95949 

26 

0-92610 

46 

0-88443 

66 

0-83473 

86 

0-98893 

6 

0-95655 

28 

0-92237 

48 

0-87970 

68 

0-82938 

88 

0-98569 

8 

0-95355 

30 

0-91855 

50 

0-87487 

70 

0-82396 

90 

0-98262 

10 

0-95053 

32 

0-91465 

52 

0-87021 

72 

0-81849 

92 

0-97962 

12 

0-94732 

34 

0-91066 

54 

0-86535 

74 

0-81293 

94 

0-97668 

14 

0-94399 

36 

0-90657 

56 

0-86042 

76 

0-80731 

96 

0-97379 

16 

0-94055 

38 

0-90239 

58 

0-85542 

78 

0-80164 

98 

0-97039 

18 

0-93697 

40 

0-89798 

60 

0-85035 

80 

0-79589 

100 

0-96808 

20 

• 

With  methyl  alcohol  solutions  of  different  concentrations  there  correspond,  on  boiling,  vapours 
richer  in  alcohol : 


Per  cent,  of  alcohol  in  solution 
Per  cent,  of  alcohol  in  vapour 


5     10     15    20     25    30    40     50     60       70       80      90         95 
g    47     57     64     69     72     78     82     86     89-6     93     96-5     98-3 


128  ORGAN  1C    CHEMISTRY 

harmful  to  the  human  organism ;  fatty  degeneration  of  the  liver  is  also  produced 
(E.  Harnack,  1912 J.1 

When  heated  with  soda  lime  or  with  oxidising  agents  it  readily  yields 
formaldehyde  and  formic  acid,  and  sometimes  carbon  dioxide ;  when  distilled 
with  zinc  dust  it  gives  CO  and  H.  With  potassium  it  forms  a  crystalline 
alcoholate,  CH3  •  OK,  CH3  •  OH,  while  with  sodium  it  gives  CH3  •  ONa, 
2CH3  •  OH,  which  loses  the  alcohol  at  170°. 

With  alkalies  and  with  salts  it  forms  additive  products,  e.  g.,  SNaOH  -f- 
6CH3  •  OH  and  CaCl2  +  4CH3  •  OH. 

Laboratory  Preparation.  Very  pure  methyl  alcohol  may  be  prepared  by 
dissolving  100  grams  of  iodine  in  1  kilo  of  commercial  80  to  85  per  cent,  methyl 
alcohol,  adding  sufficient  caustic  soda  solution  to  decolorise  the  liquid,  and 
slowly  distilling  or  rectifying. 

INDUSTRIAL  PREPARATION.  Methyl  alcohol  is  obtained  industrially  by  the  dry 
distillation  of  wood,  it  being  a  bye- product  in  the  manufacture  of  acetic  acid  (q.  v. ).  The 
liquid  products  of  the  distillation  contain  much  water,  about  6  to  8  per  cent,  of  acetic 
acid,  1  to  1-5  per  cent,  of  methyl  alcohol,  0-1  to  0-4  per  cent,  of  acetone,  and  a  certain 
amount  of  tar.  After  the  removal  of  the  tar,  the  liquid  is  neutralised  with  lime  and  dis- 
tilled, this  yielding  dilute  (about  10  per  cent. )  methyl  alcohol  solution  contaminated  with 
various  products,  especially  acetone,  tar,  etc.  The  liquid  is  next  distilled  with  about 
2  per  cent,  of  lime)  in  a  rectifying  apparatus  (see  later :  Ethyl  alcohol).  The  resxiltant 
product  constitutes  crude  methyl  alcohol  (wood  spirit),  which  is  almost  colourless  at  first, 
but  becomes  brownish-red  in  the  air;  its  specific  gravity  is  about  0-816,  and  it  contains 
about  80  per  cent,  of  methyl  alcohol,  10  to  14  per  cent,  of  acetone,  and  small  proportions 
of  other  impurities  (acetaldehyde,  formaldehyde,  allyl  alcohol,  furfural,  methyl  ethyl 
ketone,  dimethylacetal,  methyl  acetate,  catechol,  ammonia,  pyridine,  methylamine,  etc.). 

To  purify  it,  it  is  diluted  with  water  to  the  sp.  gr.  0-935  (about  40  per  cent.),  left  for 
several  days,  and  after  the  superficial  tarry  layer  which  collects  has  been  removed  it  is 
treated  with  2  per  cent,  of  lime  and  distilled  almost  completely.  The  distilled  product  is 
mixed  with  0- 1  to  0-2  per  cent,  of  sulphuric  acid  and  rectified,  the  foreshots  (rich  in  acetone 
and  allyl  alcohol)  and  tailings  (rich  in  wood-oil  and  high  boiling-point  ketones  of  almost  no 
practical  value),  being  collected  separately.  The  large  fraction  (about  50  per  cent.)  which 
distils  over  slowly  at  62°  to  65°  serves  in  most  countries  for  denaturing  ethyl  alcohol  and 
for  making  formaldehyde,  and  another  portion  (about  25  per  cent. )  which  is  distilled  still 
more  carefully  at  65°  to  66°  constitutes  the  pure  methyl  alcohol  used  for  synthetic  organic 
products.  The  last  traces  of  acetone  are  removed  by  distillation  in  presence  of  a  little 
calcium  hypochlorite,  which  forms  chloroform  with  the  acetone  (also  with  methyl  alcohol ). 
Better  purification  is  effected  by  transforming  the  alcohol  into  an  ester  (e.  g.,  the  oxalate, 
by  treatment  with  concentrated  sulphuric  acid  and  potassium  dioxalate),  which  is  easily 
separated  from  the  impurities ;  by  hydrolysing  the  ester  with  KOH,  distilling  and  rectify- 
ing, pure  methyl  alcohol  is  obtained.  The  acetone  may  also  be  got  rid  of  by  combining 
the  alcohol  with  CaCl2,  giving  the  compound  CaCl2,  4CH3  •  OH,  which  is  stable  at  100°, 
so  that  the  acetone  may  be  distilled  off  at  56°  together  with  the  other  impurities;  the 
residue  is  then  decomposed  with  water  and  the  pure  methyl  alcohol  distilled.  The 
empyreumatic  odour  may  be  removed  by  filtration  through  wood  charcoal. 

According  to  Farkas's  patent  (Ger.  Pat.  166,360,  1904)  alcohol  of  92  to  95  per  cent, 
purity  is  obtained  direct  if  the  vapours  from  the  distillation  of  wood,  while  still  hot,  are 

1  In  Berlin  at  the  end  of  1911  some  dozens  of  people  died  suddenly  and  some  hundreds 
incurred  serious  danger  from  drinking  spirits  consisting  to  the  extent  of  four-fifths  of  methyl 
-alcohol.  The  trial,  investigations  and  reports  which  followed  in  1912  (Scharmach  case)  showed 
that  even  before  then  there  were  numerous  cases  of  poisoning  of  workmen  due  to  respiration  of 
vapours  of  methyl  alcohol  during  the  manufacture,  or  to  ingestion  of  spirits  adulterated  with  this 
alcohol.  As  little  as  8  grams  suffices  to  cause  serious  effects  on  the  eyesight,  and  larger  do'ses 
lead  to  blindness.  Nearly  three  hundred  cases  of  such  poisoning  were  registered  in  the  literature 
up  to  1904.  Direct  post-mortem  detection  of  methyl  alcohol  is  difficult,  but  abnormal  quantities 
of  formic  acid  appear  in  the  bladder,  brain,  stomach,  etc.  In  1911  abnormally  large  quantities 
of  methyl  alcohol  were  imported  into  Italy,  these  being  probably  added  as  adulterant  to  ethyl 
alcohol ;  this  abuse  was  met  by  the  imposition  of  taxation  equal  to  that  on  ethyl  alcohol,  namely, 
£10  16s.  per  anhydrous  hectolitre. 


TESTS    FOR    MET.HYL    ALCOHOL  129 

passed  through  hot  NaOH  solution  (15°  to  20°  Be.),  which  fixes  the  acid  products,  and  then 
into  hot  fatty  acids,  which  fix  the  methyl  alcohol ;  the  alcohol  recovered  from  these  fatty 
acids  is  purified  by  passing  the  vapours  into  milk  of  lime  and  then  rectifying. 

To  ascertain  if  the  alcohol  still  contains  acetone,  10  c.c.  of  it  is  treated  with  caustic 
soda  and  an  aqueous  solution  of  iodine  in  potassium  iodide ;  no  turbidity  due  to  iodof orm 
should  be  formed  for  some  time.1 

USES  AND  STATISTICS.  Methyl  alcohol  is  used  mainly  for  the  manu- 
facture of  formaldehyde  and  of  methyl  derivatives  (dimethylaniline,  methyl 
chloride  and  bromide,  etc.)  used  in  making  aniline  dyes.  It  is  employed  also 
in  the  preparation  of  different  varnishes  as  a  substitute  (partial  or  total)  for 
spirit  and  oil  of  turpentine,  in  preparing  perfumed  hair  lotions,  etc.,  and  for 
denaturing  spirit  (ethyl  alcohol). 

In  1902,  Germany  produced  5000  tons  of  the  pure  alcohol,  of  which  1151 
tons  were  exported,  and  imported  4273  tons  of  the  crude  product.  In  1909 
7000  tons  of  the  crude  alcohol  were  imported  and  in  1910,  9000  tons,  one- 
half  from  Austria  and  one-half  from  North  America  at  £24  per  ton  in  1909 
and  £30  in-  1910.  In  the  latter  year  2000  tons  of  pure  methyl  alcohol  were 
exported  at  £40  per  ton. 

The  Italian  importation  and  exportation  were  as  follows  (hectolitres)  : 

1908     1910     1911     1913     1914     1915     1916     1917 

Importation  ...         25        640       2916       296        1611       275  2 

Exportation  .         .         .662          17  5         11  11          10         32 

For  France  the  quantities  are  (tons)  : 

1913  1914  1915  1916 

Importation      .         .         .     2269         1307        1767-5       1702 
Exportation      .         .         .       139-5          48-6        95-7  31 

1  Tests  for  Methyl  Alcohol.  When  pure  it  should  leave  no  residue  on  evaporation,  should 
not  have  an  acid  reaction  towards  litmus,  and  should  not  contain  ethyl  alcohol,  which  may  be 
detected  as  follows  :  a  little  of  the  liquid  is  heated  with  sulphuric  acid,  diluted  with  water  and 
distilled,  the  distillate  being  treated  with  permanganate,  then  with  sulphuric  acid,  and  finally 
with  sodium  hydrogen  sulphite ;  if  ethyl  alcohol  is  not  present  this  liquid  will  not  give  a  violet 
coloration  with  fuchsine  solution.  Acetone  and  ethyl  alcohol  may  also  be  detected  by  the 
iodoform  reaction  (Lieben's  reaction  :  see  below  and  also  p.  121 ).  Proportions  of  2  to  3  per  cent, 
of  methyl  alcohol  may  be  detected  by  Scudder  and  Riggs's  reaction  (1906),  which  consists  in 
treating  10  c.c.  of  the  liquid  at  25°  with  5  c.c.  of  concentrated  sulphuric  acid  and  5  c.c.  of  saturated 
permanganate  solution,  decolorising  (after  two  minutes)  with  sulphurous  acid  solution  and  boiling 
until  all  smell  of  sulphur  dioxide  or  acetaldehyde  disappears.  This  liquid  is  then  tested  for 
formaldehyde  by  adding  a  few  centigrams  of  resorcinol  to  2  c.c.  and  pouring  1  c.c.  of  pure  con- 
centrated sulphuric  acid  to  the  bottom  of  the  liquid ;  a  blue  ring,  due  to  the  formaldehyde  formed 
from  the  methyl  alcohol,  forms  at  the  surface  of  separation  of  the  two  liquids.  Deniges  (1910) 
detects  as  little  as  1  per  cent,  of  ethyl  alcohol  by  heating  the  methyl  alcohol  with  bromine  water 
and  testing  for  the  acetaldehyde  formed  with  fuchsine  solution  decolorised  with  S02  (see 
Aldehydes ). 

Estimation  of  the  methyl  alcohol  in  the  commercial  product  is  effected  by  the  Krell-Kramer 
method  :  30  grams  of  phosphorus  tri-iodide  is  placed  in  a  flask  furnished  with  a  long  reflux  con- 
denser, down  which  is  poured,  drop  by  drop,  10  c.c.  of  the  methyl  alcohol ;  after  a  short  time  the 
methyl  iodide  formed  is  distilled  from  a  water-bath  into  a  graduated  cylinder  containing  a 
little  water;  when  the  distillation  is  completed,  the  condenser  is  rinsed  out  with  water  and  the 
volume  of  the  methyl  iodide  under  the  water  measured  at  15°;  5  c.c.  of  pure  methyl  alcohol 
gives  7-19  c.c.  of  methyl  iodide. 

The  acetone  is  estimated  by  Kramer's  method  :  in  a  50  c.c.  graduated  cylinder  with  a  ground 
stopper  are  placed  10  c.c.  of  a  2N-caustic  soda  solution,  then  1  c.c.  of  the  alcohol,  and,  after 
shaking,  5  c.c.  of  a  2N-iodine  solution.  After  a  short  time  10  c.c.  of  ether  free  from  alcohol 
is  added,  the  liquid  shaken  and  then  allowed  to  stand ;  the  volume  occupied  by  the  ether  is 
read  off,  an  aliquot  part  of  it  evaporated  to  dryness  on  a  tared  watch-glass  and  the  iodoform 
crystals  dried  in  a  desiccator  and  weighed  :  394  parts  CHI3  correspond  with  58  of  acetone. 

A  good  commercial  methyl  alcohol  should  contain  not  more  than  0-7  per  cent,  of  acetone  and 
at  least  95  per  cent,  of  the  alcohol ;  it  should  distil  within  1° ;  5  c.c.  of  0-1  per  cent,  permanganate 
solution  should  not  be  decolorised  immediately  when  treated  with  5  c.c.  of  the  alcohol,  and  25  c.c. 
of  the  alcohol,  mixed  with  1  c.c.  of  an  acetic  acid  solution  of  bromine  (1  part  Br  in  80  parts  of 
50  per  cent,  acetic  acid )  should  give  a  yellow  solution. 

VOL.  ii.  9 


130  ORGANIC    CHEMISTRY 

In  1909  Great  Britain  imported  22,600  hectolitres,  and  in  1910  20,200 
(47,200);  in  1910  the  value  of  the  exports  was  £20,000. 

The  United  States  exported  35,000  hectolitres  in  1906,  76,100  in  1910, 
and  92,000  (£180,000,  t.  «.,  about  £2  per  hectolitre  for  the  crude,  about  80  per 
cent,  alcohol) ;  in  1914  the  output  of  crude  methyl  alcohol  was  about  500,000 
hectolitres. 

Pyroligneous  alcohol  of  90  per  cent,  strength  (French)  was  sold  before  the 
war  at  £4  12s.  per  100  kilos;  that  of  92  to  93  per  cent,  strength  (English)  at 
£4  17s.  6d. ;  and  that  of  95  to  96  per  cent,  strength  for  lacs  at  £5  Is.  Qd. ;  the 
purest  methyl  alcohol,  free  from  acetone,  cost  £7  per  100  kilos.  During  the 
European  War,  the  price  in  Italy  rose  to  £48  per  100  kilos. 

.  ETHYL  ALCOHOL,   C2H5  •  OH   (Ethanol,  Spirit  of  Wine) 

This  is  found  occasionally  in  nature  (as  butyric  ester  in  Pastinaca  saliva  and  Heracleum 
giganteum)  and  sometimes  as  an  abnormal  product  in  certain  vegetables  and  animals,  whilst 
it  is  easily  formed  by  the  alteration  (fermentation)  of  various  organic  vegetable  substances 
(saccharine  juices,  fruits,  etc.).  It  has  hence  been  known  from  the  most  remote  times. 
Aqua  vitse  or  spirit  of  wine,  obtained  by  distilling  alcoholic  beverages,  was  used  as  early 
as  the  eighth  century,  and  gave  rise  to  an  industry  which  acquired  great  renown  in  the 
province  of  Modena  in  the  fourteenth  century.  Various  European  races  learnt  the  use  of 
aqua  vitse  from  the  custom  introduced  everywhere  by  the  soldiers,  who  consumed  large 
quantities  of  it  during  the  wars  of  the  Middle  Ages.  Very  soon,  however,  the  northern 
peoples,  who  did  not  produce  aqua  vitae  from  wine,  began  to  prepare  alcohol  by  suitable 
transformations  of  the  starch  in  the  cereals  abounding  in  their  countries.  By  the  beginning 
of  the  nineteenth  century  alcoholic  liquors  (exciting  and  enfeebling  the  nervous  system 
and  the  brain)  were  spread  over  the  whole  of  the  civilised  world  and  produced  the  terrible 
social  scourge  of  alcoholism,  much  more  disastrous  in  its  material  and  moral  consequences 
than  all  the  other  maladies  that  afflict  humanity  (see  later,  Alcoholism).  Later,  however, 
alcohol  gradually  acquired  agricultural  and  industrial  importance  owing  to  its  increasing 
practical  applications  in  the  arts  and  industries.  Since  1830  Germany  has  extended  the 
manufacture  of  potato  spirit,  and  in  many  districts  great  agricultural  advantages  have 
followed  the  cultivation  of  this  vegetable,  since  the  waste  products  from  the  distilleries 
serve  as  nourishment  for  large  numbers  of  cattle — a  source  of  great  direct  and  indirect 
profit  owing  to  the  abundant  supply  of  stable  manure,  which  increases  the  fertility  of  the 
land  and  hence  also  the  crops. 

PROPERTIES.  When  pure,  it  is  a  colourless  liquid  with  a  characteristic 
odour,  sp.  gr.  0'7937  at  15°,  0'80625  at  0°;  it  boils  at  78'3°  (or  at  13°  under 
21  mm.  pressure),  and  its  vapour  is  stable  at  300°;  its  vapour  pressures  (mm. 
of  mercury)  at  different  temperatures  are  as  follows  : 

Temperature    .         .  — 10°        0°        20°       30°       40°       50°       60°       70°       80°     100° 
Pressure  .         .      6-5      12-24      44        78      133-4   219-8     350      541       812      1692 

Its  heat  of  evaporation  is  216'5  cals. 

At  a  very  low  temperature  it  gives  a  glassy  mass,  which  at  —  135°  is  con- 
verted into  another  solid  mass  m.-pt.  —  117°  (enantiotropy,  Vol.  I.,  p.  208). 

When  concentrated  (absolute)  it  is  extremely  hygroscopic,  and  it  mixes 
with  water  or  ether  in  all  proportions.  To  obtain  absolute  alcohol,  i.  e.,  abso- 
lutely free  from  water,  fractional  distillation  is  not  sufficient,  since  at  78'15° 
an  aqueous  alcohol  containing  95'57  per  cent,  of  alcohol  by  weight  distils ;  1 

1  In  the  following  table,  a  is  the  percentage  of  alcohol  by  volume  in  an  aqueous  solution,  6  the 
boiling-point,  c  the  percentage  of  alcohol,  and  d  the  percentage  of  water,  by  volume  in  the  vapour : 

abed  abed 

6  95-9°  35-75  64-25  60  81-7°  78-17  21-83 

10  92-6°  51  49  70  80-8°  81-85  18-15 

20  88-3°  66-2  33-8  80  79-9°  86-49  13-51 

30  85-7°  69-26  30-74  90  79-1°  91-80  8-2 

40  84-1°  73-45  26-55  95-57  78-15°  95-57  4-43 

50  82-8°  74-95  24-05  97-6  78-4°  97-6  2-4 


PROPERTIES    OF    ALCOHOL  131 

the  higher  alcohols  also  give  mixtures  with  water  which  boil  at  lower  tem- 
peratures than  the  corresponding  pure  alcohols.  If  benzene  is  mixed  with 
alcohol,  the  latter  may  be  obtained  pure,  since  a  mixture  of  water  and  benzene 
first  distils  over,  then  alcohol  (at  64*8°),  then  alcohol  and  benzene  (68'2°),  and 
finally  pure  alcohol. 

Usually  absolute  alcohol  is  obtained  by  distilling  the  ordinary  90  to  96  per 
cent,  alcohol  over  calcined  potassium  carbonate  or  over  anhydrous  (i.  e.,  cal- 
cined) copper  sulphate,  redistilling  over  lime,  and  finally  over  baryta  or  a  little 
sodium  or  calcium ;  or  it  may  be  left  over  powdered  aluminium  until  hydrogen 
ceases  to  be  evolved.  The  aldehydes  of  the  alcohol  may  be  separated  by  boiling 
with  5  per  cent,  of  caustic  soda. 

If  alcohol  contains  a  little  water,  it  becomes  turbid  when  mixed  with 
benzene,  carbon  disulphide,  or  paraffin  oil,  and  turns  white,  calcined  copper 
sulphate  blue,  and  barium  hydroxide  is  precipitated  on  addition  of  baryta, 
the  latter  dissolving  only  in  the  absolute  alcohol. 

A  mixture  of  53'9  vols.  of  alcohol  with  49'8  of  water  gives  100  vols.,  the 
contraction  of  3'7  per  cent,  being  due  to  the  formation  of  a  labile  compound, 
(C2H5  *  OH)18,  H20  (or  2H20,  etc.).  It  is  a  good  solvent  for  resins,  oils,  colour- 
ing-matters, varnishes,  ethereal  essences,  and  many  other  substances,  and 
dissolves  sulphur  and  phosphorus  to  a  slight  extent ;  it  coagulates  proteins  and 
diffuses  through  porous  membranes  more  rapidly  than  water.  It  dissolves 
and  gelatinises  soaps.1 

It  unites  with  various  salts  and  alkalis  as  alcohol  of  crystallisation  (KOH, 
LiCl,  CaCla,  MgCl2)  (see  p.  128). 

It  oxidises  easily,  giving  aldehyde  and  acetic  acid,  e.  g.,  with  potassium 
dichromate,  MnO2,  or  even  H2S04,  or  oxygen  in  presence  of  platinum,  or  with 
micro-organisms  if  the  solution  is  dilute.  With  concentrated  nitric  acid,  it  gives 
various  oxidation  products  and  with  the  dilute  acid,  glycollic  acid.  Alcoholic 
solutions  of  caustic  alkalis  turn  brown,  since  they  are  partially  resinified  by  the 
aldehyde  which  forms  first  and  which  acts  as  a  reducing  agent.  Chlorine  gives 
acetaldehyde  and  various  intermediate  chlorinated  products.  In  a  red-hot  tube 
it  decomposes,  giving  hydrogen  and  large  proportions  of  hydrocarbons  and  acids. 
With  sodium  it  gives  sodium  ethoxide  in  the  form  of  a  white  powder  (see  later). 

Absolute  alcohol,  which  plays  an  important  part  in  organic  syntheses,  is 
poisonous  and  rapidly  produces  death  when  injected  into  the  blood.  It  is  a 
powerful  antiseptic,  especially  at  70  per  cent,  concentration,  which  most  readily 
coagulates  protoplasm  and  proteins. 

The  complete  combustion  of  1  kilo  of  pure  alcohol  (C2H5  •  OH  -f-  60  = 
2CO2  +  3H2O)  generates  7193  Cals.  and  96  per  cent,  alcohol,  about  6750  Cals. 

Alcohol  may  be  detected  even  in  traces  (1  :2000)  by  means  of  Lieben's 
iodoform  reaction  (see.  pp.  121  and  129).  This  reaction  is  also  given  by  acetone, 
isopropyl  alcohol,  and  the  aldehydes;  according  to  Buchner  (1905)  it  is 
preferable  to  heat  the  alcoholic  liquid  with  a  little  paranitrobenzoyl  chloride, 
which  forms  crystals  of  ethyl  paranitrobenzoate,  N02  •  C6H4  •  C02C2H5, 
m.-pt.  57°.  In  Rimini's  reaction,  the  liquid  is  heated  with  sulphuric  acid  and 
a  dilute  solution  of  potassium  dichromate  :  the  green  colour  of  the  solution  and 
the  odour  of  acetaldehyde  are  sufficiently  characteristic,  but  the  reaction  may 

1  Solid  Alcohol  is  nothing  but  a  soapy  mass  formed  from  about  20  per  cent,  of  water,  20  per 
cent,  of  soap  (sodium  stearate),  and  60  per  cent,  or  more  of  alcohol;  it  burns  like  liquid  alcohol, 
but  leaves  a  residue. 

A  richer  product  may  be  prepared  by  heating  and  stirring  100  parts  of  96  per  cent,  alcohol 
at  60°,  dissolving  1  part  of  stearine  and  adding  0-5  part  of  a  30  per  cent,  aqueous  sodium  hydroxide 
solution — just  sufficient  to  make  it  redden  phenolphthalein.  Some  use  a  sodium  soap  charged 
with  silicate  (500  per  cent.).  A  solid  alcohol  that  burns  without  leaving  a  residue  may  be 
obtained  by  dissolving  20  to  40  parts  of  collodion  in  100  parts  of  alcohol;  others  add,  instead, 
25  parts  of  a  25  per  cent,  solution  of  cellulose  acetate  in  acetic  acid,  and  shake,  the  crust  of  solid 
alcohol  which  separates  being  squeezed  out. 


132 

be  confirmed  by  distilling  a  few  drops  of  the  liquid  and  treating  the  distillate 
with  a  little  sodium  nitroprusside  and  a  drop  of  piperidine,  a  beautiful  blue 
coloration  being  obtained  if  acetaldehyde  is  present. 

The  manufacture  of  alcohol  became  one  of  the  great  chemical  industries 
when  a  scientific  explanation  was  obtained  of  the  phenomena  governing  the 
transformation  of  starch  and  sugar.  Fermentation,  although  known  from  the 
most  ancient  times,  remained  unexplained  up  to  the  nineteenth  century,  and 
it  is  solely,  or  largely,  owing  to  the  studies  of  Caignard  de  Latour  and  Schwann, 
Turpin,  Schroeder,  Liebig,  Pasteur,  Nageli,  Cohn,  de  Bary,  and,  more  recently, 
Duclaux,  Buchner,  etc.,  that  the  phenomena  of  fermentation  are  now  completely 
explained  and  rationally  regulated. 

In  1836  Caignard  de  Latour  and  Schwann  found  that  the  fermentation  of  wine  and 
beer  is  strictly  dependent  on  the  germination  of  microscopic  fungi  which  multiply  in  the 
must  or  wort.  Turpin  supposed  that  these  fungi  are  nourished  by  the  sugar,  producing, 
as  the  excreta  of  their  vital  action,  alcohol  and  carbon  dioxide.  In  1838  Liebig  held 
that  this  transformation  of  sugar  is  caused  by  a  special  intermolecular  movement  due  to 
substances  contained  in  the  ferment  itself  (microscopic  fungus). 

Pasteur,  in  1872,  showed  that  certain  ferments  that  live  at  the  expense  of  the  oxygen 
of  the  air  and  can  decompose  sugar  into  water  and  carbon  dioxide,  when  they  are  immersed 
in  saccharine  liquids,  being  no  longer  able  to  assimilate  oxygen  from  the  air,  extract  it 
from  the  sugar,  resolving  the  molecule  of  the  latter  into  alcohol  and  carbon  dioxide. 
Although  Nageli,  in  1879,  had  attempted  to  reconcile  the  hypotheses  of  Liebig  and  Pasteur, 
yet  up  to  a  few  years  ago  all  fermentative  phenomena  were  interpreted  on  the  basis  of  the 
ideas  enunciated  by  Pasteur.  Progress  in  the  fermentation  industry  proceeded,  pari 
passu,  with  that  of  bacteriology.1 

1  Bacteriology  is  the  science  which  studies  morphologically  and  biologically  the  very  small, 
unicellular,  vegetable  organisms  which  are  propagated  with  immense  rapidity  by  segmentation. 
The  cell  is  formed,  as  in  the  higher  organisms,  of  an  extremely  thin  membrane  which  permits 
all  the  osmotic  phenomena  (see  Vol.  L,  p.  80),  and  encloses  the  protoplasm  in  which  no  central 
nucleus  is  visible,  but  in  which  there  occur  scattered  granules  (of  starch  and  other  substances), 
fat  globules,  vacuoles  containing  cell-sap,  and  sometimes  crystals  (e.  g.,  of  sulphur),  while  in 
certain  bacteria  the  protoplasm  holds  various  colouring-matters  in  solution.  The  temperature 
most  favourable  to  their  vitality  varies,  according  to  the  species,  from  5°  to  40°;  they  live, 
however,  in  a  latent  condition,  at  very  low  temperatures,  although  they  do  not  reproduce,  and 
they  usually  die  at  about  70°  (excepting  the  spores,  see  below).  As,  in  general,  they  do  not 
contain  chlorophyll,  they  are  nourished  by  complex  organic  substances  already  elaborated  by 
other  organisms  and  hence  soluble  or  capable  of  being  rendered  soluble  (sugars,  organic  and 
inorganic  ammonium  salts,  etc.) ;  in  this  they  are  clearly  differentiated  from  vegetable  organisms 
and  approximate  more  to  the  animals.  Nutrient  matter  for  bacteria  always  contains  phosphorus, 
sulphur,  potassium,  and  calcium,  and,  in  certain  cases,  magnesium  and  manganese.  They  are 
able  to  take  the  carbon  they  require  for  their  nutrition  even  from  ethyl  alcohol  in  a  concentra- 
tion of  4  per  cent.  (180  species  of  bacteria  are  capable  of  such  assimilation)  or  from  methyl  alcohol 
at  the  same  concentration  (25  species),  and  the  nitrogen  also  from  inorganic  ammonium  salts, 
nitrates,  urea,  and  even  free  ammonia,  the  nutriment  being  made  up  with  mineral  substances, 
such  as  monopotassium  phosphate,  magnesium  sulphate,  etc.  (e.  g.,  Epicoccum  purpurescens 
requires  nitrates  and  magnesium  salts  for  the  formation  of  its  purple  colouring  matter,  while 
Aspergillus  niger  requires  manganese  salts,  etc.).  All  bacteria  live  well  and  reproduce  rapidly 
in  meat-broth  or  nutrient  gelatine.  They  tolerate  more  easily  alkaline  than  acid  media,  and  direct 
sunlight  kills  many  species  of  bacteria,  even  pathogenic  ones.  As  a  result  of  their  vital  actions, 
substances  are  sometimes  formed  which  kill  the  bacteria  themselves.  Different  antiseptics 
have  various  actions  on  different  bacteria,  or  else  only  a  specific  action  on  certain  of  them.  The 
reproduction  of  bacteria  takes  place  ordinarily  by  segmentation,  that  is,  when  the  cell  has  reached 
a  certain  length  a  thin  wall  forms  in  the  middle  and  divides  the  cell  into  two  new  ones ;  these 
divide,  in  their  turn,  so  that  the  reproduction  of  these  organisms,  which  increase  in  geometrical 
proportion  (1,  2,  4,  8,  16,  32,  etc.),  proceeds  with  prodigious  rapidity  and  yields  millions  of 
individuals  in  a  few  hours.  The  universal  distribution  of  bacteria  is  thus  easily  understood. 
When  the  vital  conditions  are  rendered  abnormal  or  difficult  for  bacteria,  in  many  of  them  there 
occurs  a  contraction  of  their  protoplasm  into  a  more  compact  mass  (at  the  centre  or  laterally, 
according  to  the  species),  which  forms  a  separate  individual,  the  spore,  much  more  resistant  to 
cold  (—  180°)  and  heat  (130°  to  140°),  and  even  to  antiseptics  than  the  corresponding  bacterial 
cell;  the  spores  can  retain  life  even  for  some  years.  Under  favourable  conditions,  the  spore 
breaks  its  envelope  and  gives  a  cell  which  reproduces  by  segmentation  like  the  original  one. 
Only  certain  rare  species  of  bacteria  are  provided  with  chlorophyll  or  other  colouring-matters 
capable  of  assimilating  carbon  dioxide  under  the  action  of  sunlight. 

These  micro-organisms,  termed  bacteria  or  schizomycetes  or  microbes,  arc  those  which  produce 


BACTERIOLOGY  133 

During  recent  times,  however,  new  facts  have  been  discovered  which  have  profoundly 
shaken  the  fundamental  basis  of  this  theory,  according  to  which  no  fermentation  is  possible, 
except  in  the  presence  of  certain  species  of  living  micro-organisms.  In  reality  certain 
special  fermentations  are  already  known  which  are  produced  by  enzymes,  i.  e.,  substances 
of  complex  chemical  compositions  which  do  not  manifest  anything  of  the  nature  of  living 
micro-organisms;  for  example,  diastase  transforms  starch  into  maltose:  2(C6H10O5)a;  + 
H20  =  zC12H22Ou.i 

Between  1896  and  1900  Buchner  succeeded  in  showing,  by  careful  experiment,  that  some 
of  these  fermentations,  which  in  the  past  could  be  induced  only  by  the  living  micro- 
organisms, may  be  effected  also  by  using  the  extract  of  the  bacteria  obtained  by  squeezing 
out,  under  great  pressure,  through  special  unglazed  porcelain  niters,  the  extract  of  the 

putrefaction  and  infectious  diseases  (cholera,  carbuncles,  typhus,  tuberculosis,  small-pox,  diph- 
theria, etc.);  they  are  classified,  according  to  their  form,  into  :  (1)  Desmobacteria  (bacillus  or 
vibrio  forms  like  small  rods);  (2)  Spherobacteria  (coca  and  micrococci  of  spherical  shape  and 
termed  diplococci  if  united  in  twos,  staphylocci  if  joined  in  bunches,  and  streptococci  if  in  strings) ; 
(3 )  Spirobacteria  (spirilla  of  twisted  shape ).  To  give  a  concrete  idea  of  their  forms  de  Bary 
described  them  as  analogous  to  a  pencil,  a  billiard  ball,  and  a  corkscrew. 

On  the  basis  of  their  different  activities  and  physiological  properties  Cohn  divided  all  the 
species  of  bacteria  into  three  characteristic  groups  :  (1)  zymogenic,  or  those  which  produce  all 
the  non-alcoholic  fermentations;  (2)  chromogenic,  which  produce  various  colouring -matters 
(red,  violet,  yellow,  etc. ) ;  (3 )  pathogenic,  which  cause  diseases  of  man  and  animals.  To  recognise 
the  latter — given  the  difficulty  of  distinguishing  them  morphologically  under  the  microscope, 
since  different  species  often  have  the  same  form  and  the  same  species  sometimes  several  forms — 
they  are  inoculated  into  the  blood  of  living  rabbits,  rats,  guinea-pigs,  etc.,  the  pathogenic  char- 
acter being  deduced  from  the  effects  produced  in  the  animals  in  two  or  three  days,  or  sometimes 
even  after  a  few  hours. 

The  lesser  diameter  (width )  of  these  unicellular  bacteria  measures  a  few  tenths  of  a  micron 
(1  micron  or  /j.  =  0-001  mm.),  and  in  rare  cases,  as  much  as  1-7  /u ;  the  greater  diameter  (length) 
is  usually  several  microns. 

If  we  wish  to  indicate  bacteria  in  a  wider  sense  of  the  term,  and  not  to  limit  them  to  the 
pathogenic  or  saprophytic  (non -pathogenic),  but  still  to  those  that  produce  all  putrefactions  and 
widen  the  limits  of  their  dimensions,  we  may  logically  divide  these  micro-organisms  into  two 
other  groups  of  similar  beings,  namely,  the  Hyphomycetes  (moulds)  and  the  Blastomycetes 
(ferments). 

The  Hyphomycetes  form  groups  of  branched  filaments  (mycelia],  which  often  subdivide  into 
portions  similar  to  bacteria,  but  the  width  of  these  always  exceeds  2^u  and  often  5/j. ;  they  multiply 
by  means  of  spores  and  four  principal  species  are  distinguished  according  to  the  mode  of  forma- 
tion of  these  spores  (conidia)  :  (1)  the  Aspergillus  species,  which  form,  at  the  extremities  of  the 
fruit  bearing  filaments  (spore-bearing  hyphce),  a  swelling  in  the  form  of  a  club  covered  with  series 
of  spores  attached  by  means  of  intermediate  sterigmata  ;  (2)  the  Mucor  species  (or  Mucedinece), 
in  which  the  spore-bearing  hyphse  which  start  from  the  mass  of  mycelia  carry  sporangia  (species 
of  capsule )  in  which  the  spores  develop ;  (3 )  the  Oidium  species  in  which  the  spores  are  formed 
directly  in  the  spore-bearing  hyphse  without  any  special  organ  of  fructification;  (4)  the  Peni- 
cillium  species,  which  is  very  common  and  has  branched  spore-bearing  hyphse  in  the  form  of  a 
brush  containing  rows  of  spores.  Aspergillus  and  Oidium  are,  however,  not  separate  species, 
but  special  sporifying  forms  of  Eurotium  and  Erysiphce  belonging  to  the  order  of  Ascomycetes. 

The  most  important  of  these  micro-organisms  for  industrial  purposes  are  the  Blastomycetes, 
i.  e.,  the  ferments  or  unicellular  fungi  which  usually  multiply  by  gemmation  (budding),  that  is, 
by  excrescences  forming  on  the  cells  and  becoming  detached  when  they  have  reached  a  certain 
size,  forming  new  cells  which  live  independently  of  the  mother-cells ;  under  abnormal  conditions, 
however,  the  ferments  multiply  also  by  means  of  spores,  four  nuclei  being  usually  formed  inside 
the  cell,  these  then  becoming  covered  with  membranes  and  dividing  the  mother-cell  into  four 
parts  forming  four  new  cells. 

The  cells  of  the  ferments  have  often  a  magnitude  greater  than  5ju,  and  the  most  important 
for  alcoholic  fermentation  form  the  family  of  the  Saccharomycetes  (see  later). 

The  extraordinary  beneficial  influence  of  the  bacteria  and  ferments  in  nature  (apart  from  the 
pathogenic  action  of  certain  of  them  on  some  of  the  higher  organisms)  is  manifested  in  the 
wonderful  destructive  activity  they  exert  on  the  refuse  and  remains  of  all  the  higher  organisms, 
converting  the  complex  substances  composing  them  into  continually  more  simple  substances 
until  they  give  C02,  H20,  NH3,  and  HN03.  These  are  the  simplest  materials  which  can  be  used 
by  vegetable  organisms  to  recommence  the  life-cycle,  since  in  nature  nothing  is  destroyed  or 
created,  but  everything  is  transformed  and  thus  life  itself  rendered  eternal. 

1  Starch,  which  is  formed  in  the  green  leaves  of  plants  under  the  action  of  sunlight  and  of 
chlorophyll,  although  an  insoluble  substance  and  very  resistant  to  various  reagents,  migrator 
during  the  night  and  accumulates  in  the  seeds,  roots  (tubers),  medulla,  etc.  We  can,  however, 
stop  the  starch  in  its  path,  and  can  explain  how  it  may  be  transported  by  the  juices  into  othes 
parts  of  the  plant.  In  fact,  various  enzymes  occur  distributed  through  plants,  and  among  these 
is  diastase  or  amylase,  which  renders  the  starch  soluble  by  transforming  it  into  soluble  (and  hence 
transportable  by  the  juices)  sugar  (maltose),  to  be  regenerated  by  an  inverse  process — unknown 
to  us — in  the  form  of  insoluble  starch  in  other  parts  of  the  plant. 


134 

ferment-cells  previously  ground  with  quartz-sand.  In  this  way  Saccharomyces  cerevisice 
(Fig.  117)  yields  maltase  (an  enzyme  occurring  also  in  germinating  barley  or  maize 
and  contained  in  Saccharomyces  octosporus),  which  hydrolyses  maltose,  transforming  it 
into  glucose;  from  beer-yeast  is  obtained  invertase  (or  invertin)  capable  of  resolving  sac- 
charose or  cane-sugar  (not  directly  fermentable)  into  fructose  and  glucose  (fermentable); 
fresh  yeast  cells  yield  zymase,  the  enzyme  capable  of  effecting  the  alcoholic  fermentation 
of  various  six-carbon-atom  sugars  (glucose,  fructose,  etc.). 

The  action  of  the  enzyme  cannot  be  attributed  to  the  still  living  protoplasm  derived 
from. the  cells  of  the  ferment,  since  the  protoplasm  may  easily  be  killed  in  a  mixture  of 
alcohol  and  ether,  and  after  this  treatment  the  enzyme  retains  its  activity.  The  action 
of  ferments  is  hence  due  to  the  enzymes  that  they  are  able  to  produce,  rather  than  to 
the  biological  phenomena  of  the  life  of  the  organisms. 

Numerous  enzymes  are  now  known  which  are  of  great  importance  in  many 
vital  functions  of  vegetable  and  animal  organisms.  It  is  not  certain  if  the 
enzymes,  with  their  large  and  complex  molecules,  are  true  proteins,  since  up 
to  the  present  they  have  not  been  obtained  chemically  pure;  all  of  them 
contain  nitrogen,  but,  as  they  are  purified  more  and  more,  the  nitrogen  content 
continually  diminishes  and  to-day  it  is  held  by  some  that  the  composition 
of  each  enzyme  approaches  that  of  the  substance  it  transforms ;  thus  diastase 
would  be  a  substance  similar  to  starch  and  poor  in  nitrogen,  whilst  the  enzymes 
that  transform  the  proteins  would  be  of  true  protein  nature.  Proteolytic 
(decomposition  of  proteins)  and  fermentative  actions  occur  only  between 
certain  limits  of  temperature  (0°  and  65°)  and  are  retarded  or  prevented  by 
certain  poisons  (e.  g.,  by  traces  of  prussic  acid  or  by  metallic  salts  that  act  on 
proteins,  like  HgCl2,  etc.,  although  they  are  more,  and  sometimes  completely, 
resistant  to  the  action  of  antiseptics  that  kill  ferments,  such  as  salicylic  acid, 
boric  acid,  ether,  etc.).  The  various  enzymes  produce  one  or  other  of  the 
following  general  reactions :  hydrolysis  (amylases,  sucrases),  coagulation 
(enzyme  of  rennet),  decomposition  (zymase  of  alcoholic  fermentation),  oxidation 
(laccase  oxidises  the  juice  of  the  lac-tree),  etc.  Enzymes  exhibit  different 
behaviour  towards  the  stereoisomerides  of  certain  hydrolysable  and  fermentable 
substances  (see  section  on  Sugars).1 

1  The  following  are  some  of  the  more  important  enzymes  : 

Diastase  (or  amylase)  occurs  abundantly  in  malt  (germinating  cereals),  but  is  found  also  in 
plants,  the  pancreas,  the  saliva,  the  liver,  the  bile,  the  blood,  the  kidneys,  and  the  mucous 
membrane  of  the  stoma'ch  and  of  the  intestines ;  it  transforms  starch  into  maltose  and 
dextrin. 

Maltase  transforms  maltose  into  glucose,  and  is  found  in  malt,  in  Saccharomyces  cerevisice,  and 
in  plants  and  animals. 

Zymase  causes  alcoholic  fermentation  of  glucose,  and  is  contained  in  yeast  and  the  alcoholic 
ferments  (Saccharomyces). 

Lactase  decomposes  milk-sugar. 

Melibiase  resolves  raffinose  (or  cane-sugar)  into  molecules  of  more  simple  sugars. 

Invertase  (sucrose,  saccharose,  or  invertin)  decomposes  saccharose  into  glucose  and  levulose, 
and  is  obtained  from  beer-yeast. 

Cytase  or  Cellase  attacks  cellulose. 

Maltodextrinase  ferments  maltodextrin. 

Dextrinase  ferments  dextrins. 

Peptase  governs  the  important  digestive  functions  of  the  stomach,  and  pcptonises  proteins. 

Tryptase  is  found  in  the  pancreas  and  contributes  to  the  peptonisation  and  decomposition 
of  the  proteins. 

Lipase  is  also  found  in  the  pancreas  and  renders  the  fats  soluble  (hydrolyses  them).       « 

Emulsin,  contained  in  bitter  almonds,  and  capable  of  decomposing  amygdalin. 

Ptyalin  is  contained  in  the  saliva  and  initiates  the  digestion  of  starchy  foods. 

Reductase  is  capable  of  effecting  reduction  phenomena,  especially  in  presence  of  aldehydes, 
and  is  hence  also  known  as  aldehydo-catalase  ;  it  decolorises  Schardinger's  reagent  (mixture 
of  methylene  blue  and  formalin).  Reductase  is  widespread  in  the  animal  kingdom  and 
occurs  in  unboiled  milk  (boiled  milk  is  detected  by  the  lack  of  this  enzyme ;  it  does  not 
decompose  water  or  decolorise  guaiacol). 

The  Oxydases  form  a  group  of  enzymes  (laccase,  tyrosinase,  cenoxydase,  catalase,  etc.)  capable 
of  effecting  oxidations  by  fixing  the  free  oxygen  of  the  air  and  transferring  it,  in  the  nascent 


ENZYMES  135 

Still  rnore  interesting  is  the  fact  that  during  an  ordinary  fermentation  the  amount 
of  sugar  fermented  does  not  depend  closely  on  the  quantity  of  living  ferment  or  enzyme ; 
thus  large  quantities  of  sugar  can  be  decomposed  by  small  quantities  of  ferment  or  enzyme. 

The  action  of  the  enzymes  and  of  the  ferments  may  be  logically  compared  with  that 

state,  to  the  substances  to  be  oxidised.  They  occur  widespread  in  the  vegetable  kingdom  and 
are  also  found  in  the  animal  kingdom,  and  their  oxidising  action  is  comparable  with  that  of 
platinum  black  (catalyst).  In  fact  the  catalase  found  in  the  blood  is  capable  of  decomposing 
H202,  giving  nascent  oxygen  and  water  (Loew,  1901).  It  is  now  found  that  the  oxydases  are 
formed  of  mixtures  of  oxygenase  and  peroxydase.  Euler  and  Bolin  (1909)  obtained  a  laccase 
of  the  Medicago  type  in  a  chemically  pure  state,  and  found  it  to  be  composed  of  calcium  salts 
and  a  small  amount  of  iron  salts  of  mono-,  di-,  and  tri-basic  hydroxy-acids,  especially  citric, 
malic,  mesoxalic,  and  glycollic  acids. 

Peroxydases  and  Oxygenases.  Schonbein  (1856)  had  observed  that  certain  vegetable  and 
animal  organisms  contain  substances  analogous  to  ferments  and  capable  of  decomposing  hydrogen 
peroxide  catalytically  with  liberation  of  oxygen,  and  also  of  accelerating  catalytically  this 
decomposition  (i.  e.,  the  oxidising  action)  in  the  same  way  that  ferrous  sulphate  does.  Loew 
(1901)  showed  that  the  first  action  is  due  to  a  special  enzyme,  catalase  (oxygenase}.  Linossier, 
in  1898,  succeeded  in  separating  from  pus  an  enzyme  free  from  oxydase  (oxygenase),  yet  capable 
of  accelerating  but  not  of  initiating  the  decomposition  of  hydrogen  peroxide;  this  he  called 
peroxydase.  The  oxydases  and  peroxydases  often  occur  together  and  they  may  be  separated 
by  heating  the  mixture  to  70°,  the  oxydase  being  thus  killed,  or,  as  was  proposed  by  Aso  of  Tokio 
(1902),  by  dissolving  the  peroxydase  in  alcohol  which  does  not  dissolve  the  oxydase,  or  by 
poisoning  the  latter  with  sodium  fluoride  or  fluosilicate.  There  are  also  several  plants  that 
contain  only  peroxydases,  among  them  pumpkins  and  horse-radish  roots  (Bach  and  Chodat, 
1903,  1906). 

The  peroxydases  are  nitrogenous  but  non-protein  substances,  and,  when  heated  with  NaOH 
give  NH3;  they  always  contain  about  6  per  cent,  of  ash,  0-8  to  1-4  per  cent,  being  aluminium 
and  0-2  to  0-6  per  cent,  manganese.  The  peroxydases  dialyse,  whilst  the  oxygenates  do  not. 
The  specific  action  of  the  peroxydases  consists  in  activating  in  a  remarkable  manner  the  oxidising 
action  of  H202  on  organic  substances,  e.  g.,  gallic  acid,  pyrogallol,  etc.;  they  activate  also  the 
action  of  the  peroxides  that  form  in  organic  substances  by  the  action  of  the  oxygen  of  the  air 
(e.  g.,  ethereal  oils,  turpentine,  etc.). 

In  1897  Bertrand  introduced  the  following  hypothesis  to  explain  the  action  of  the  oxydases  : 
the  latter  are  regarded  as  hydrolysable  manganese  protein  compounds,  in  which  the  manganese, 
in  the  manganous  condition,  is  the  transmitter  of  oxygen  from  the  air  to  the  oxidisable  substance ; 
the  manganese  dioxide  formed  would  then  be  again  reduced  by  the  protein  acid  radical,  the 
original  manganous  protein  compound  being  regenerated.  Bach  and  Chodat  have,  however, 
found  manganese  in  the  peroxydases,  although  these  are  not  direct  oxidising  agents. 

The  peroxydases  have  no  oxidising  action,  unless  a  peroxide  is  present.  They  do  not  turn 
fresh  guaiacol  tincture  blue,  but  after  some  hours  this  change  does  occur,  the  tincture  having 
formed  peroxide,  which  may  be  detected  by  starch  and  potassium  iodide  solution.  Whilst  the 
peroxydases  accelerate  the  decomposition  of  very  dilute  H202,  this  destroys  them  if  concen- 
trated. In  1908  J.  Wolff  obtained  the  reactions  of  the  peroxydases  by  traces  of  ferrous  sulphate 
or  copper  sulphate.  The  oxidising  action  of  the  oxygenases  (which  have,  however,  not  yet 
been  obtained  free  from  peroxydases,  although  the  latter  are  known  free  from  oxygenases)  is 
only  weak  and  is  strongly  activated  by  addition  of  peroxydase.  On  the  other  hand,  it  seems 
established  that  there  are  two  species  of  peroxydases  existing,  the  one  activating  strongly  the 
oxygenases  and  feebly  the  decomposition  of  H202,  and  the  other  behaving  in  the  opposite  way. 
The  character  of  the  oxydases  themselves  is  indicated  by  the  specific  action  of  one  or  the  other 
species  of  peroxydase.  Indeed,  Bertrand  had  in  1896  extracted  from  certain  plants,  e.  g.,  young 
potato  tubers,  an  oxydase  which  differed  from  all  others  in  not  oxidising  phenols  or  the  aromatic 
amines,  whilst  it  oxidised  and  blackened  tyrosine,  which  is  not  altered  by  the  ordinary  oxydases 
or  even  by  H202  combined  with  one  of  the  ordinary  peroxydases.  Bach  (1906)  succeeded  in 
separating  the  specific  peroxydase  from  tyrosinase  and  in  showing  that  this  peroxydase  is  capable 
of  causing  the  oxidation  of  tyrosine  only  when  mixed  with  the  corresponding  oxygenase  or  in 
presence  of  H202  alone.  Hence  the  action  of  tyrosinase  is  due  to  the  specific  action  of  its  peroxy- 
dase. Bach  holds  further  that  in  the  phenomena  of  respiration  of  organisms,  oxidation  due  to 
oxydases  plays  no  part,  since  this  leads  to  true  condensations,  to  syntheses  of  more  complex 
products ;  for  respiratory  phenomena  there  should  exist  enzymes  of  a  type  not  yet  known  and 
capable  of  decomposing  and  oxidising  the  reserve  materials  of  the  organism  (fats,  carbohydrates, 
etc.,  which  are  not  oxidised  by  oxydases). 

At  the  present  day  the  catalytic  action  of  the  enzymes  is  explained  as  due  to  small  quantities 
of  metals  which  they  contain ;  thus  the  important  action  of  the  haemoglobin  of  the  blood  (which 
fixes  the  oxygen  in  the  lungs  in  a  labile  condition  and  transports  it  to  all  parts  of  the  organism ) 
appears  to  be  due  to  the  small  quantities  of  iron  present,  this  inducing  the  decomposition  of  the 
food  materials ;  further,  the  synthetic  action  of  the  peroxydases  is  perhaps  due  to  the  manganese 
they  contain  (see  above),  just  as  the  important  synthetic  functions  of  chlorophyll,  according  to 
Willstatter's  recent  work,  appears  to  be  owing  to  the  magnesium  present  in  it.  Recently  (1910) 
Bach  has,  however,  succeeded  in  preparing  very  active  oxydases  and  peroxydases  free  from  iron 
and  manganese,  so  that  the  true  explanation  of  the  activity  of  these  enzymes  remains  to  be 
discovered. 


136 


ORGANIC    CHEMISTRY 


of  the  inorganic  catalysts  (Vol.  I.,  pp.  71,  319),  which  only  produce  an  enormous  increase  in 
the  velocity  of  reaction,  in  our  case,  of  the  decomposition  of  sugar.  That  these  organic 
catalysts  have  an  action  really  similar  to  that  of  the  inorganic  catalysts  can  be  shown  by 
certain  other  interesting  facts. 

Some  years  ago  Duclaux  succeeded  in  producing  alcoholic  fermentation  by  dilute 
alkali;  Traube  in  1899  transformed  sugar  into  alcohol  by  means  of  finely  divided  platinum 
alone  at  160° ;  while  Schade  in  1906  converted  an  alkaline  solution  of  glucose,  in  absence 
of  enzyme,  quantitatively  into  acetaldehyde  and  formic  acid  (C6H12O6  =  2C2H4O  + 
2CH2O2),  and  these  products,  under  the  catalytic  influence  of  rhodium,  are  transformed 
quantitatively  into  C02  and  alcohol  (perhaps  the  formic  acid  first  gives  CO2  and  H2,  the 
latter,  in  the  nascent  state,  reducing  the  aldehyde  to  alcohol).1 

Further,  in  chemical  equilibria  (Vol.  I.,  p.  64),  the  action  of  catalysts  in 
reversible  reactions  is  regulated  by  the  temperature  and  concentration  con- 
ditions, and  the  same  phenomenon  is  met  with  in  the  case  of  enzymes  :  indeed, 
when  diastase  has  converted  a  certain  quantity  (dependent  011  the  temperature) 
of  starch  into  maltose,  the  hydrolytic  change  is  arrested  (i.  e.,  equilibrium  is 
reached  in  the  reversible  reaction  :  starch  $  maltose) ;  if,  however,  part  of  the 
maltose  is  fermented  into  alcohol  and  C02,  the  equilibrium  is  disturbed  and 
the  diastase  hydrolyses  a  further  quantity  of  starch.  Also  at  temperatures 
above  55°,  diastase  forms  dextrin  in  preference  to  maltose.  An  analogous 
phenomenon  is  observed  in  the  hydrolysis  of  amygdalin  by  emulsin.  It  has 
already  been  mentioned  that  maltase  transforms  maltose  first  into  glucose, 
but  when  a  certain  proportion  between  these  two  products  is  reached,  the 
hydrolysis  ceases  owing  to  equilibrium  being  attained  :  C12H22On  +  H20  1^ 
2C6H12O6,  and  the  transformation  proceeds  further  only  when  the  glucose  is 
removed  by  alcoholic  fermentation ;  Emmerling  has  realised  the  inverse  reaction 
by  displacing  the  equilibrium  by  addition  of  glucose  (in  which  case  isomaltose 
is  produced). 

Also  in  the  action  of  maltase  on  amygdalin,  Emmerling  succeeded  in 
producing  the  reverse  reaction,  and  at  the  St.  Louis  Exhibition  in  1904  he 
showed  a  fine  specimen  of  amygdalin  prepared  synthetically  by  an  enzymic 
process.2 

1  Buchner  and  Meisenheimer  (1909)  explain  the  action  of  ferments,  from  the  chemical  point 
of  view,  by  the  addition  of  a  molecule  of  water  to  the  sugar  and  abstraction  of  an  atom  of  oxygen 
by  the  ferment,  so  that  there  results,  as  an  unstable  intermediate  product,  a  di-primary  alcohol, 
which,  in  its  turn,  is  immediately  decomposed  into  H2  and  2  mols.  of  dihydroxyacetone ;  the 
last  product  is  able  to  decompose  into  C02  and  alcohol,  while  the  hydrogen  continues  to  trans- 
form fresh  quantities  of  sugar  into  the  dihydric  alcohol,  and  so  on.  Boysen-Jcnsen  (1909) 
finds  that  the  reactions  for  dihydroxyacetone  are  given  by  fermentations ;  the  decomposition 
would  hence  take  place  thus  : 


CH2OH 

CHOH 

CHOH 

CHOH 

CHOH 


CHO 

Glucose 


+  H20  =  0  -f 


CHjOH 

CHOH 

CHOH 

CHOH 

CHOH 


CH2OH 

Di-primary 
alcohol 


CH2OH 
CO 

CH2QH 
CH2OH 


CO 
CH2OH 

2  mols.  of 
Dihydroxyacetone 


-co,  + 


CH3 
CH,  •  OH 


CH3 
CH2  •  OH 


2  mols. 
of  alcohol 


C6H5  •  CH(CN)  •  C6HU06 

Glucoside  of  phenylgly- 

collie  nitrile 
or,  more  completely  : 

2C0H120«      +       HCN 

Glucose  Hydrocyanic 

acid 


C6H1206        ^        C20H27NOn  +  H20 

Maltase  Amygdalin 


2H2NO 


C6H5  •  CHO  £  2H20 

Benzal- 
dehyde 

Franzen  and  Steppuhn  (1911)  have  shown  experimentally  that,  in  the  enzymic  conversion 
of  sugar  into  alcohol  and  carbon  dioxide,  formic  acid  is  produced  as  an  intermediate  product. 


BIOGEN     HYPOTHESIS  137 

So  that  with  one  and  the  same  enzyme,  analytic  and  synthetic  processes 
can  be  effected.  Cremer  obtained  glycogen  (C6H1005)y  from  levulose  (C6H1206) 
by  means  of  an  extract  of  yeast,  and  Hanriot,  Kastle,  and  Loevenhart  prepared 
monobutyrin  and  butyl  acetate  synthetically  by  means  of  lipase.  The 
enzymes  also  effect  the  so-called  asymmetric  syntheses,  i.  e.,  they  give  optically 
active  compounds  containing  asymmetric  carbon  (1908). 

Also  of  interest  is  the  fact  that  a  single  ferment  may  contain  various  enzymes ; 
thus,  from  Saccharomyces  cerevisice,  maltase  and  invertase  may  be  extracted 
easily  and  also  zymase,  though  with  more  difficulty  (by  grinding  the  yeast 
with  powdered  quartz  and  forcing  the  extract  through  a  porcelain  filter  under 
high  pressure). 

These  recent  discoveries  on  the  reversibility  of  the  reactions  effected  by 
enzymes  are  of  great  importance,  as  it  was  at  first  thought  that  enzymes  or 
ferments  in  general  were  capable  of  causing  only  decompositions  and  not 
synthetic  reactions,  whereas  their  analogy  with  inorganic  ferments  is  now 
complete.  The  discoveries  are  all  the  more  remarkable,  since  the  same  pheno- 
menon of  vitality— in  the  single  cell  as  in  more  complex  organisms — may  be 
reduced  to  an  enzymic  phenomenon ;  that  is  to  say,  the  exchange  of  material 
in  the  organism  (decomposition,  recomposition,  growth)  takes  place  by  means 
of  these  organic  catalysts,  which  cause  the  decomposition  of  food,  preparing 
various  complex  materials  which  form  the  organism  itself,  and  at  the  same 
time  generating  the  energy  manifested  in  the  vitality,  enzymic  phenomena 
being  always  exothermic.  This  hypothesis  may,  with  advantage,  be  substituted 
for  the  too  abstract  biogen  1  hypothesis,  to  explain  vital  phenomena. 

This  result  is  in  harmony  with  Wohl  and  Schade's  theory,  according  to  which  sugar  when  fer- 
mented passes  through  various  intermediate  products,  especially  lactic  acid,  this  in  its  turn, 
being  resolved  into  acetaldehyde  and  formic  acid;  the  latter  would  then  give  carbon  dioxide 
and  hydrogen,  the  nascent  hydrogen  transforming  the  acetaldehyde  into  ethyl  alcohol  (see 
Note,  p.  136). 

Similar  phenomena  were  observed  by  Neuberg  and  Kerb  (1913).  Thus,  by  the  action  of 
enzymes,  pyruvic  acid  (CH3  •  CO  •  C02H)  is  transformed  readily  and  completely  into  C02  and 
acetaldehyde,  with  simultaneous  formation  of  ethyl  alcohol  (this  is  facilitated  by  presence  of 
glycerol),  probably  from  the  aldehyde.  Further,  to  the  extent  of  85  per  cent,  butyraldehyde 
and  valeraldehyde  are  converted  by  enzymes  into  the  corresponding  alcohols  and  o-ketobutyric 
acid  into  propyl  alcohol. 

1  Hypotheses  of  Biogen,  Toxins,  and  Genesis  of  Life.  The  physical  and  physiological 
basis  of  life  resides  especially  in  the  protoplasm,  the  semi-fluid,  almost  always  colourless,  refractive 
substance — insoluble  in  water— which  everywhere  constitutes  the  essential  part  of  the  cell. 
Protoplasm  is  formed  principally  of  protein  substances,  whilst  it  is  thought  that  the  fats  and 
carbohydrates  are  not  active  components.  To  the  protoplasm  is  attributed  the  fundamental 
property  of  vitality,  i.  e.,  the  exchange  of  material,  but  it  is  not  known  how  its  components — • 
the  proteins — can  have  such  properties  or  in  what  physico-chemical  aggregation  of  the  proteins 
(the  plastidules  and  bionomads  are  regarded  as  morphological  components  or  units  of  protoplasm ) 
they  have  their  origin. 

In  animals  one  of  the  principal  functions  of  the  blood  is  that  of  supplying  the  respiratory 
needs  of  the  tissues  in  virtue  of  the  haemoglobin  contained  in  the  blood  of  vertebrates  [besides 
fibrmogen,  serum-albumin,  and  paraglobulin  ;  whilst  with  the  invertebrates  there  are  echino- 
chrom,  chlorocruorin,  hcemoerylhrin,  hcemocyanin  (containing  copper),  and  pinnoglobin  (con- 
taining manganese ),  which  have  the  same  functions  as  haemoglobin] ;  it  is  formed  of  a  protein 
substance  united  with  a  ferruginous  compound,  which  takes  up  oxygen  at  the  respiratory 
surfaces  of  the  organism  (skin,  bronchi,  and  lungs),  and  brings  it  into  close  contact  with  the 
tissues. 

The  vital  processes  of  the  organism  being  due  to  the  exchange  of  material  in  the  cells  full  of 
protoplasm,  the  biogenic  hypothesis  assumes  that  this  is  brought  about  by  a  very  complex,  labile 
compound,  which,  by  being  continually  decomposed  and  reconstituted,  maintains  the  inter- 
change uninterruptedly.  By  many  this  compound  is  called  living  albumin,  but  Max  Verworn 
(1895  and  1902)  regards  this  as  an  unsuitable  name,  and  does  not  think  it  has  been  shown 
to  be  a  true  albuminoid,  although  it  is  a  nitrogenous  substance;  there  are  possibly  several 
substances  in  a  state  of  labile  combination  and  these  he  calls  molecules  of  biogen. 

It  has  been  observed  that  in  organisms,  as  in  parts  of  them,  vitality  ceases  when  oxygen 
is  eliminated,  many  of  them  subsequently  (the  frog  even  after  twenty-five  hours)  recovering  it 
in  presence  of  oxygen.  From  this  arise  two  hypotheses  :  (1)  the  molecule  of  biogen  becomes 
labile,  and  hence  gives  rise  to  decompositions  and  recompositions,  that  is,  to  the  vital  process — 
since  it  unites  transitorily  with  oxygen;  (2)  oxygen  serves  only  to  oxidise  or  eliminate  the 


138  ORGANIC    CHEMISTRY 

In  order  to  ascertain  if  a  given  action  is  due  to  enzymes  or  to  organised 
ferments,  the  liquid  is  passed  under  pressure  through  a  Chamberland  porous 

decomposition  products  of  the  biogen  (admittedly  labile),  and  when  there  is  no  oxygen,  these 
products  are  not  eliminated,  so  that  the  decomposition  and  recomposition  of  the  biogen  are 
arrested.  By  experiments  on  the  frog  Verworn  has  shown  that  the  former  hypothesis  is  the 
more  probable. 

Since,  in  the  vital  process,  under  the  action  of  oxygen,  it  is  especially  the  carbon  dioxide 
that  is  eliminated,  often  along  with  lactic  acid,  water,  etc.,  whilst  the  elimination  of  nitrogenous 
substances  does  not  increase,  it  may  be  assumed  that  biogen  is  constituted  of  a  benzene  nucleus 
with  lateral  chains  of  carbohydrate  and  aldehydic  character  and  with  an  oxygen-carrying 
nitrogenous  group  which  fixes  the  oxygen  of  the  air  (just  as  NO  gives  N02  in  the  lead-chambers 
of  sulphuric  acid  works)  and  gives  it  up  to  the  lateral  chain,  which  is  oxidised  (Ehrlich's  side- 
chain  hypothesis,  1882-1902)  to  C02,  lactic  acid,  H20,  etc.,  these  being  eliminated;  the  nitro- 
genous group,  thus  reduced,  remains  united  with  the  benzene  group,  which,  with  new  food, 
forms  the  biogen  molecule,  this  being  again  decomposed  by  oxygen  and  so  on.  The  digested 
food -materials  carry,  with  the  blood,  new  materials  to  the  regeneration  of  biogen  (without 
food,  death  ensues),  the  oxygen  then  effecting  the  changes  described  above.  The  seat  of  the 
biogen  lies  in  the  liquid  protoplasm  of  the  cell  (not  in  its  nucleus),  into  which  oxygen  enters  in  the 
state  of  labile  combinations  not  yet  defined,  but  capable  of  giving  it  up  when  needed  :  these 
compounds  are  more  stable  in  the  cold  than  in  the  hot,  and  are  those  that  carry  on  the  vitality 
during  prolonged  fasts.  These  reserve  materials  are  probably  formed  by  the  decomposition 
of  the  food  by  means  of  intracellular  enzymes,  which  form  the  connecting-link  between  the 
living  substance  (biogen)  and  the  non-living  (foods),  transforming  the  latter  into  the  former. 

The  biogen  hypothesis  is  opposed  by  that  of  the  enzymes  as  factors  of  the  vital  process  and, 
given  the  varied  nature  of  the  phenomena  and  of  the  chemical  transformations  occurring  in  the 
living  organism,  and  the  variety  of  the  numerous  chemical  groups  forming  a  protein  molecule, 
it  is  perhaps  imprudent  to  refer  all  these  phenomena  to  a  single  compound,  biogen,  when  we 
already  know  different  enzymes  which  certainly  effect  well -investigated,  definite  reactions. 
From  the  action  of  different  enzymes  on  the  protein  complex  forming  the  protoplasm  of  the 
cell,  there  results  the  many-sided  phenomenon  of  vitality.  In  certain  cases  it  is  possible  to  go 
still  further,  as  it  must  be  admitted  that  many  synthetic  and  analytic  phenomena  of  organic 
substances  (e.  g.,  the  fermentation  of  sugar)  take  place  even  without  protoplasm,  by  the  direct 
action  of  the  enzyme  alone  (see  p.  134). 

Further,  by  simple  catalytic  actions,  it  is  now  possible  to  effect  artificial  fertilisation  (arti- 
ficial parthenogenesis) ;  for  example,  by  treating  unfertilised  eggs  of  the  sea-urchin  with  solutions 
of  various  chlorides,  best  of  all,  magnesium  chloride,  Loeb  (1899  and  1900)  obtained  living 
larvae;  Giard  (1904)  studied  the  artificial  parthenogenesis  of  the  star-fish  (Asteria  rubens); 
Tichomiroff  (1886  and  1902)  and,  better,  Quajat  at  Padua  (1905)  obtained  partial  artificial 
parthenogenesis  of  the  virgin  eggs  of  the  silk-worm. 

Most  interesting  of  all  are  the  investigations  on  serotherapy  which  have  led  to  the  most 
unexpected  results  when,  instead  of  the  observations  being  limited  to  the  bacteria,  the  poisonous 
or  beneficial  substances  which  they  elaborate  or  secrete  have  been  considered.  These  toxins 
or  antitoxins  secreted  by  bacteria  or  formed  in  animal  organisms  also  appear  to  be  enzymes, 
exhibiting,  however,  their  activity  in  phenomena  of  a  different  and  more  complex  nature. 

Since  1902  Arrhenius,  in  conjunction  first  with  the  head  of  the  German  school,  Ehrlich, 
and  later  with  that  of  the  Danish  school,  Madsen,  has  devoted  himself  to  the  interpretation 
of  serotherapy,  making  effectual  use  of  all  the  modern  laws  of  physical  chemistry.  He  has 
succeeded  in  following  and  controlling  the  formation  and  action  of  toxins  and  antitoxins  in  the 
animal  organism  by  empirical  mathematical  formulas,  calculated  beforehand  from  the  results 
of  previous  experiments ;  it  is  not  improbable  that  the  time  will  soon  arrive  when  from  these 
empirical  formulae,  suitably  co-ordinated,  rational  formulas  will  be  derived  leading  to  new  and 
important  natural  laws,  from  which  general  pathology  will  obtain  great  principles  rendering  it 
possible  for  man  and  other  animals  to  be  immunised  against  the  attacks  of  pathogenic  bacteria. 
Then,  and  only  then,  will  man  have  triumphed  over  the  microbe. 

By  injecting  more  or  less  poisonous  substances  (toxins)  into  the  animal  organisms,  the  so- 
called  anti-bodies  (antitoxins)  are  formed  in  the  blood,  but  their  formation  is  probably  incomplete 
in  consequence  of  the  laws  of  chemical  equilibria  discovered  by  Guldberg  and  Waage  (Vol.  I., 
p.  65). 

The  corresponding  antitoxins  are  known  for  only  a  few  poisons.  Those  of  solanine  and 
saponin  (1901 )  and  of  morphine  (antimorphine)  (1903)  nave  been  sought  for  in  vain  by  inoculating 
guinea-pigs  and  rabbits,  so  that  these  three  poisons  are  not  to  be  regarded  as  toxins.  From 
castor-oil  seeds  ricin  has  been  extracted — a  toxin  for  which  the  corresponding  antiricin  is  known ; 
also,  seeds  of  Abrus  prcecatorius  and  Eobinia  pseudacacia  yield  the  poisons  abrin  and  robin, 
for  which  the  corresponding  antitoxins  have  been  obtained.  Animals  also  produce  anti-bodies 
of  non-poisonous  substances;  thus,  if  any  cells  whatsoever  are  injected  into  the  blood,  anti- 
bodies are  more  or  less  rapidly  produced  which  have  a  special  destructive  action  on  these  cells. 
Also  by  injecting  rennet  (which  coagulates  milk)  an  antirennet  is  obtained  which  is  able  to  prevent 
the  coagulating  action  of  the  rennet. 

From  pathogenic  bacteria  are  obtained  anti -bodies  (by  inoculation)  to  certain  proteolytic 
enzymes:  in  1893  Hildebrandt  found  an  anti-body  to  emulsin  and  Gessard  (1901)  prepared 
an  anti-body  to  tyrosinase  (see  above);  from  the  serum  of  a  goose  inoculated  with  pepsin,  H.  Sachs 
(1902)  obtained  an  antipepsin  ;  A.  Schiitze  (1904)  obtained  antilactase  by  making  subcutaneous 


TOXINS    AND    ANTITOXINS  139 

porcelain  filter,  which  retains  the  ferment  cells,  but  not  the  enzymes;  the 
filtered  liquid  is  then  examined  to  ascertain  if  it  still  produces  the  enzymic 
action.  Alternatively,  the  liquid  may  be  mixed  with  chloroform,  which  arrests 
all  cellular  life,  but  does  not  act  on  the  enzymes. 

and  intermuscular  inoculations  with  the  lactase  of  kephir  (which  see),  and  similarly  were  prepared 
anti-bodies  to  cynarase,  zymase,  urease,  and  the  fibrin  and  pancreatic  ferments. 

It  is  difficult  to  establish  a  limit  or  any  essential  difference  between  enzymes  or  ferments  • 
and  toxins,  and  the  preparation  of  anti-bodies  to  all  these  active  substances  is,  perhaps,  only 
a  matter  of  time.  The  an ti -bodies  are  divided  into  two  classes,  according  as  they  are  obtained 
by  inoculation  of  homogeneous  solutions  (toxins)  or  of  emulsions  of  bacteria  or  cells  (red  blood 
corpuscles),  etc.  The  anti-body  formed  by  the  inoculation  of  a  homogeneous  solution  com- 
bines with  the  toxin  of  the  latter,  forming  an  innocuous  substance,  which  is  called  an  antitoxin 
if  soluble  or  a  precipitin  if  insoluble.  The  injection  of  bacteria  sometimes  leads  to  the  formation 
of  anti-bodies  capable  of  dissolving  the  bacteria  themselves  (from  which  they  are  derived)  and 
these  anti-bodies  are  then  termed  lysins  (bacteriolysins).  There  may  also  be  formed  anti-bodies 
which  agglutinate  the  inoculated  cells,  i.  e.,  agglutinins,  but  this  depends  on  the  presence  of 
salts.  The  cholesterin  and  lecithin  of  the  organism  often  form  part  of  the  toxin  or  antitoxin. 
Cholesterin,  for  example,  acts  as  an  antitoxin  to  tetanolysin  and  other  lysins.  According  to 
Metchnikoff  it  is  the  leucocytes  (white  corpuscles )  which  produce  the  antitoxins,  but  this  has  not 
been  rigorously  proved,  although  Wright  has  shown  that  certain  anti -bodies  (opsonins)  exhibit 
their  activity  against  bacteria  only  in  presence  of  leucocytes. 

That  the  action  between  toxins  and  antitoxins  resembles  chemical  neutralisation  was  assumed 
at  the  time  of  the  discovery  of  the  first  diphtheritic  antitoxin  by  Behring  and  Kitasato  in  1890, 
and  was  supported  by  the  German  school  with  Ehrlich  at  its  head.  From  1893,  however,  the 
French  school  (Roux,  Vaillard,  Metchnikoff)  and  also  Buchner  held  that  the  antitoxins  exert 
a  physiological  action,  exciting,  as  it  were,  the  organic  tissues  to  resist  the  attacks  of  these 
poisons  (toxins).  When,  however,  Ehrlich  showed  that  the  agglutinating  action  of  ricin  on  the 
red  blood  corpuscles  (suspended  in  physiological  serum,  that  is,  in  0-9  per  cent.  NaCl  solution) 
could  be  annulled  by  simply  adding  antiricin,  and  because  he  showed  that  the  neutralisation 
of  the  action  of  a  given  quantity  of  toxin  required  the  presence  of  a  proportionate  amount  of 
antitoxin,  most  scientific  men  abandoned  the  physiological  hypothesis.  Ehrlich's  more  recent 
studies  on  the  action  of  two  arsenical  compounds  on  the  toxins  have  led  to  the  cure  of  sleeping- 
sickness  and  probably  to  that  of  syphilis  (by  means  of  the  product  606).  In  suitable  conditions 
of  temperature,  etc.,  the  original  toxins  may  be  regenerated  from  the  antitoxins  by  a  reversible 
process  (Reversible  Reactions,  Vol.  L,  p.  66);  this  was  shown  by  Morgenroth  (1905)  by  dis- 
sociating the  antitoxin  with  a  little  HC1  and  destroying  the  anti-body  at  100°,  thus  obtaining 
the  original  toxin.  So  that  validity  can  no  longer  be  ascribed  to  the  hypothesis  of  Behring 
(1890),  Nernst  (1904),  and  Biltz,  Much,  and  Siebert  (1905),  according  to  which  the  toxins  are 
absorbed  by  the  colloidal  antitoxins  and  then  destroyed. 

The  toxins  and  antitoxins,  although  colloidal  substances,  diffuse  easily  and  give  osmotic 
pressures  according  to  van  't  Hoff's  law. 

Toxins  diffuse  through  water  and  gelatine  much  more  rapidly  than  antitoxins,  so  that  a 
mixture  of  the  two  bodies  can  be  separated  into  its  components.  The  difference  in  the  rapidity 
of  diffusion  depends  on  the  molecular  magnitudes  (according  to  E.  W.  Reid,  haemoglobin  has  a 
molecular  weight  of  48,000).  The  molecular  weights  of  the  antitoxins  would  be  10  to  100  times 
as  great  as  those  of  the  toxins. 

The  velocity  of  reaction  of  the  different  toxins  does  not  depend,  as  Morgenroth  supposed, 
on  catalytic  actions,  but,  as  Arrhenius  and  Madsen  showed,  on  the  temperature,  and  is  regulated 
by  a  law  deduced  from  thermodynamical  considerations  based  on  van  't  Hoff's  laws  of  solutions. 

A  number  of  other  factors  of  the  vitality  of  the  organism — digestion  of  food,  assimilation 
of  carbon  dioxide  by  plants,  development  of  the  egg,  production  of  alcohol  during  the  fermenta- 
tion of  sugar,  etc. — are  due  to  enzymes  or  toxins  and  antitoxins,  the  actions  of  which  are  regulated 
by  the  laws  of  chemical  equilibria  and  of  the  velocity  of  reaction,  and  are  perhaps  not  discon- 
nected from  catalytic  phenomena  or  from  reactions  similar  to  or  identical  with  those  assumed 
by  the  biogen  and  side-chain  hypotheses. 

Further,  the  studies  of  0.  Lehmann  and  of  S.  Leduc  (1896)  on  Liquid  Crystals,  accord- 
ing to  which,  under  certain  conditions,  solutions  of  substances  can  assume  the  form  of  crystals 
or  of  cells  that  grow,  multiply,  and  die,  like  actual  organisms  (see  Vol.  I.,  p.  117),  furnish  a 
probable  explanation  of  the  transition  from  organic  substances  to  organised  bodies.  Thus, 
after  what  has  been  stated  above,  the  entire  cycle  of  the  genesis  of  life  can  be  comprehended,  from 
the  transformation  of  inorganic  substances  into  organic  (see  pp.  1,  35,  and  111,  and  later :  Synthetic 
Alcohol )  and  of  these  into  organised  (or  living ),  by  hypotheses  based  on  scientific  facts.  It  still 
remains,  however,  to  explain  the  origin  of  the  inorganic  world,  terrestrial  and  extra-terrestrial, 
the  answer  of  science  being  that,  in  accordance  with  Lavoisier's  law,  nothing  is  created  and  nothing 
destroyed,  so  that  the  inorganic  world  has  always  existed  and  is  eternal,  and  eternal  also  is  its 
continuous  evolution.  This  is  the  actual  limit  of  human  knowledge,  which,  in  its  imperfection, 
cannot  explain  the  infinite  and  the  eternal.  No  metaphysical  philosophy  has  succeeded  in 
obtaining  a  final  clue  to  this  secret  of  eternity,  since  it  is  not  a  plausible  or  even  rational  explana- 
tion to  refer  the  eternity  of  the  inorganic  world  to  a  hypothetical,  abstract,  supernatural  being 
who  created  everything  from  nothing,  in  contradiction  to  the  fundamental  laws  of  positive 
science,  the  first  of  all  of  these  being  those  of  the  conservation  of  mass  and  of  energy. 


140  ORGANIC    CHEMISTRY 

A  liquid  containing  an  enzyme  is  coloured  blue  by  the  addition  of  an  alcoholic 
solution  of  guaiacum  resin,  previously  mixed  with  a  drop  of  hydrogen  peroxide. 
The  enzymes  are,  as  a  rule,  destroyed  by  boiling. 

During  recent  years  numerous  experiments  have  been  made  on  fermentation  by  means 
of  filtered  extracts  of  ferments  free  from  cells.  The  components  of  such  extracts  have  been 
studied  in  various  ways  and  attempts  made  to  precipitate  fractionally  various  enzymes 
(e.  g.,  by  acetone  or  colloidal  ferric  hydroxide);  most  of  these  precipitates  lose,  however, 
much  of  their  fermentative  power,  and  for  the  latter  to  be  a  maximum  a  necessary  condition 
seems  to  be  the  presence  of  the  co-enzyme,  which  may  be  separated  from  the  enzyme  by 
fractional  precipitation.  According  to  Ivanoff  (1910)  alcoholic  fermentation  by  means 
of  zymase  appears  to  take  place  in  three  phases  :  (1)  depolymerisation  of  the  glucose; 
(2)  the  action  of  a  soluble  co-enzyme,  syntase,  yielding  a  phospho-organic  compound 
(compound  of  phosphoric  acid  with  a  triose  resulting  from  the  depolymerisation  mentioned), 
(see  notes  on  pp.  136  and  147),  and  (3)  resolution  of  the  phospho-organic  compound  with 
generation  of  alcohol,  by  the  action  of  alcoholase  (slightly  soluble  co-enzyme  of  zymase). 

Since  1899  various  attempts  have  been  made  to  extract  enzymes  from  fresh  yeast 
(containing  75  per  cent,  of  water)  by  plasmolysis  with  solutions  of  salts  or  glycerine  or  in 
presence  of  chloroform,  etc.  (Lintner,  Hahn,  De  Meulmestre,  Rinckleben,  van  Laar), 
for  twenty  to  thirty  hours  at  25°,  but  liquids  of  little  activity  were  thus  obtained.  A.  von 
Lebedeff  (1912)  obtains  better  results  by  simple  maceration  for  two  hours  at  35°  or  for 
six  hours  at  25°,  and  if  either  co-enzyme  concentrated  in  a  vacuum  or  disodium  phosphate 
is  added  to  the  liquid  thus  obtained,  a  highly  active  fermenting  medium  is  produced.  The 
maceration  method  may  be  applied  also  to  yeast  dried  at  150.1 

A  number  of  attempts  have  been  made,  without  marked  success,  to  prepare  enzymes 
by  chemical  means  away  from,  and  independently  of  yeast  cells.  However,  A.  D.  Bar 
(U.S.  Pat.  1,051,061,  applied  for  in  1909  and  granted  in  1913)  obtains  an  enzyme  of  great 
catalytic  activity  by  molecular  scission  of  protein  substances  with  alkali  and  acid;  thus, 
pepsin  is  treated  for  twenty-four  hours  with  ammonia,  and,  after  removal  of  the  latter, 
for  five  days  with  acetic  acid,  distillation  of  the  latter  then  leaving  a  brown,  hygroscopic 
powder  which  is  soluble  in  water  and  insoluble  in  alcohol,  ether,  or  chloroform,  and  exhibits 
very  active  enzymic  properties. 

Certain  substances  exist  which  increase  or  enhance  the  actions  of  various  enzymes; 
thus,  according  to  Hoyer,  Tanaka,  Falk,  and  Hamlin  (1913),  the  inactive  zymogen  of  the 
lipase  of  castor-oil  seeds  is  transformed  into  active  enzyme  by  manganese  sulphate,  although 
other  oxidising  agents  give  either  negative  or  but  slight  effects. 

INDUSTRIAL  PREPARATION  OF  ALCOHOL.  As  already  mentioned, 
the  prime  materials  are  saccharine  or  starchy  substances ;  the  latter,  by  the 
action  of  enzymes  (diastase  and  maltase),  are  transformed  into  maltose  and 
glucose,  and  then  by  the  action  of  the  zymase  contained  in  yeast-cells  (species 
Saccharomyces,  see  pp.  134  and  146)  the  glucose  is  transformed,  to  the  extent 
of  95  per  cent.,  into  alcohol  and  C02,  with  evolution  of  heat. 

The  treatment  of  the  starchy  materials  is  carried  out  as  follows  :  the 
starch  is  obtained  from  various  prime  economic  materials,  namely,  maize 
(especially  in  Italy,  Hungary,  ^nd  America),  potatoes  (Germany,  France, 
England,  and  Russia;  attempts  to  introduce  the  potato  industry  into  Italy 
have  as  yet  come  to  nothing) ;  cereals  (Russia  and  England) ;  rice  (England, 
Japan,  China,  Italy). 

There  are  two  practical  processes  :    (1 )  the  action  of  dilute  mineral  acids 

1  Diamalt  or  Diaslofor.  Of  great  industrial  importance  are  very  active  diastases  obtained 
as  more  or  less  concentrated  extracts  of  barley  malt  (see  later,  Beer),  these  being  used  as  con- 
centrated foods  or  strengthening  agents  in  cases  of  chlorosis,  bronchitis,  incipient  phthisis,  etc. 
Large  use  is  made  of  diamalt,  diastofor,  etc.,  which  are  highly  concentrated  malt  extracts  em- 
ployed in  the  textile  industry  for  dissolving  starch  and  removing  the  dressing  from  textile  fabrics 
(see  later,  Textile  fibres)  and  also  in  baking,  the  degradation  of  the  starch  of  the  flour  which  it 
initiates  facilitating  the  subsequent  action  of  the  yeast. 

These  extracts  contain  60  to  70  per  cent,  of  reducing  sugars  (three-fourths  maltose)  and 
5  to  7  per  cent,  of  nitrogenous  substances ;  they  are  often  adulterated  with  glucose,  dextrin,  etc. 


ALCOHOL  FROM  STARCH        141 

in  the  hot,  and  (2)  the  action  of  certain  hydrolytic  enzymes  (like  diastase 
contained  in  malt}. 

(1)  Transformation  of  starch  by  dilute  acids.     In  this  transformation  starch  yields 
glucose    almost    quantitatively:      (C6H10O5)n    (starch)  +  wH20  =  nC6H12O6;     we    shall 
deal  more  in  detail  with  this  process  later  on,  in  the  section  on  Glucose.     At  present  only 
the  second  process  will  be  considered. 

(2)  Transformation  of  starch  by  means  of  enzymes.     Of  the  enzymes,  that  which  is 
of  the  most  service  industrially,  is  diastase.      It  is  formed  more  especially  during  the 
early  stages  of  the  germination  of  cereals  (maize,  barley,  etc.),  and  this  germinated  grain 
forms  malt,  which  is  most  favoured  by  a  temperature  of  45°  to  55°  in  its  transformation 
of  starch  into  dextrins  [amylodextrin,  erythrodextrin,  achroodextrin,  (C12H20010)z]  and 
into  maltose  and  isomaltose,  C12H22On. 

As  has  been  already  mentioned  (p.  136),  this  reaction  is  regulated  by  the 
laws  of  chemical  equilibria,  and  depends  especially  on  the  temperature  :  between 
45°  and  50°  maltose  is  preferably  formed,  and  at  about  60°,  dextrin. 

We  have  already  noticed  how  maltose  is  transformed  into  glucose  by  means 
of  maltose,  and  how  the  chemical  equilibrium  is  displaced,  by  gradually  trans- 
forming the  glucose  into  alcohol  by  the  zymase  of  the  yeast  during  fermentation. 

Of  the  various  malts  used  industrially,  that  of  barley  is  the  most  active,  then  follow 
wheat  and  rye,  and,  finally,  maize;  the  last-named  is  one-third  less  active  than  that  of 
barley,  but  owing  to  its  low  price  has  practical  advantages,  and  in  Italy  is  the  one  most 
commonly  used. 

In  describing  the  industry  of  brewing,  we  shall  deal  in  detail  with  the  practical  manu- 
facture of  malt,  and  we  would  refer  the  reader  to  that  section  for  a  description  of  the 
preparation  of  maize  malt,  which  does  not  differ  from  that  of  barley  malt. 

As  regards  the  use  of  chlorine  dioxide  to  increase  the  germinative  power  of  maize, 
as  proposed  by  Effront,  see  Vol.  I.,  p.  186. 

The  starchy  matters  forming  the  starting  materials  of  the  alcohol  industry  (cereals, 
potatoes,  etc.)  cannot  be  subjected  to  the  action  of  diastase  unless  their  starch  is  first 
transformed  into  a  semi-solution  (starch-paste)  by  treating  with  water  or  steam  at  a  high 
temperature;  the  starch-granules  swell  and  then  burst  and  readily  assimilate  water 
(potato  starch  at  65°,  maize  starch  at  75°,  barley  starch  at  80°).  The  materials  are  hence 
first  macerated  or  ground,  and  then  extracted  with  hot  water,  to  be  subjected  subsequently 
to  saccharification  with  malt  and  finally  to  alcoholic  fermentation. 

The  following  Table  gives  the  amounts  of  starchy  and  extractive  matters  per  100  kilos 
of  various  materials,  together  with  the  theoretical  yields  of  alcohol : 

Starchy  and  , ,     ,    , 

extractive  matters 

Wheat       .         .         .         .  65-68  kilos  32-34  kilos 

Maize         ....  62-67  „  31-33  „ 

Barley       ....  63-65  „  30-32  „ 

Rye            .         .         .         .  66-69  „  34-35  „ 

Rice           ....  78-82  „  39-43  „ 

Durra        ....  61-64  „  30-32  „ 

Green  potatoes  .         .         .  18-20  „  9-10  „ 

Dry  potatoes      .         .         .  68-70  „  34-35  „ 

In  washed  potatoes  the  starch  is  calculated  from  their  specific  gravity  (see  later  :  Starch). 

In  cereals  and  potatoes  the  content  of  starch  may  be  determined  as  follows  :  200  grams 
of  potatoes  (75  grams  of  ground  cereal)  are  heated  in  a  flask  with  600  c.c.  of  water  and 
10  c.c.  of  hydrochloric  acid  (sp.-  gr.  1-2  =  4-7  grams  HC1)  for  ten  hours  at  90°,  the  volume 
made  up  to  1  litre  and  3-5  grams  of  the  HC1  neutralised  with  caustic  soda  (leaving  1  gram 
free);  the  whole  is  poured  into  a  larger  flask,  a  few  grams  of  beer-yeast  being  added  and 
the  flask  kept  at  25°  for  two  or  three  days  until  the  fermentation  is  over,  when  half  of  the 
liquid  is  distilled  and  the  alcohol  estimated  in  the  distillate  by  means  of  the  specific  gravity. 
100  kilos  of  starch  yield  practically  63-5  litres  of  alcohol.  This  method  gives  also  the 


142 


ORGANIC    CHEMISTRY 


yield  of  alcohol  (other  methods  for  the  exact  determination  of  starch  are  given  in  the 
chapter  on  Starch). 

The  fresh  potatoes  are  washed  free  from  stones  and  earth  in  an  Eckert  mechanical 
washer  (Fig.  105),  passing  first  into  a  rotating  sieve,  E,  which  removes  the  stones  and, 
by  means  of  the  blades,  F,  carries  the  potatoes  into  the  tank,  A,  through  which  water 
flows  and  in  which  they  are  stirred  by  the  vanes,  C,  fixed  to  a  rotating  axis ;  the  latter 

is  inclined  in  such  a  way  that  the 
potatoes  are  gradually  forced  to 
the  far  end  of  the  tank,  where 
a  rotating  disc,  furnished  with 
perforated  blades,  G,  collects  them 
and  removes  them  from  the  tank. 
A  bucket  elevator  raises  them  to 
the  opening  of  a  Pauksch's  im- 
proved form  of  the  conical  Henze 
autoclave  (Fig.  106),  which  is 
made  of  sheet-iron,  has  a  volume 
of  2500  to  3000  litres,  and  takes 
about  1500  to  3000  kilos  of 

FIG.  105  potatoes ;  in  this  they  are  treated 

for  an  hour  or  more  with  steam 

at  2-5  to  3-5  atmos.  pressure.  Such  an  apparatus  may  also  be  used  for  treating  maize 
and  other  cereals,  and  gives  a  much  denser  wort  than  was  previously  obtained  when 
steam  at  100°  was  used;  in  addition,  it  effects  a  better  dissolution  of  the  starch,  and 
is  of  advantage  to  manufacturers  in  countries  where  the  alcohol  tax  is  based  on  the  volume 
of  wort  fermented  (or  of  the  fermenting  vats).  The  steam  is  passed  in  at  the  top  by  the 
tube  b,  and  is  distributed  uniformly  over  the  interior  by  means  of  a  perforated  pipe 
(shown  dotted  at  c),  the  tap,  g,  at  the  bottom 
being  left  open  to  discharge  the  condensed  water. 
When  the  whole  mass  is  hot,  steam  begins  to 
issue  from  this  tap  and  drives  out  all  the  air. 
The  tap  is  then  shut,  and  the  pressure,  shown  by 
the  manometer,  e,  soon  rises  to  3  atmos.  After 
about  forty-five  minutes  at  this  pressure  (tem- 
perature 135°),  the  conversion  is  complete. 
With  damaged  or  frozen  potatoes,  the  steam  is 
allowed  to  issue  for  an  hour  from  the  tap,  g, 
before  raising  the  pressure,  and  steam  is  then 
passed  in  by  the  pipe  b'  as  well.  A  pressure 
higher  than  3  atmos.  turns  the  mass  brown, 
owing  to  caramelisation  of  the  maltose.  To 
discharge  the  apparatus,  the  pressure  is  main- 
tained at  its  maximum  and  connection  made 
with  the  discharge  pipe,  i,  by  opening  the  valve, 
h.  At  the  bottom  of  the  cone,  just  above  k,  is 
a  horizontal  disc  of  cutting  grids,  through  which 
the  whole  of  the  mass  is  forced  by  the  steam- 
pressure  and  thus  converted  into  a  paste;  the 
pipe  i  carries  it  to  the  coolers  and  then  to  the 
wort  vessels,  where  suitable  stirrers  complete  the 
gelatinisation  of  the  mass. 

In  order  to  avoid  danger  of  explosion,  the  Henze  autoclaves  should  be  tested  once  a 
year  to  ascertain  if  they  are  capable  of  withstanding  the  pressure  employed,  since  they 
may  become  weakened  at  rusted  parts. 

Maize,  rice,  and  cereals  are  also  treated  in  the  Henze  apparatus,  but  with  the  addition 
of  110  to  140  kilos  of  water  per  100  kilos  of  cereals,  since  these  contain  less  water  (15  per 
cent.)  than  potatoes  (75  per  cent.),  and  without  the  water  the  desired  fluidity  of  the  starch 
would  not  be  obtained.  The  volume  of  the  autoclave  is  350  litres  per  100  kilos  of  maize. 
If  a  pressure  of  5  atmos.  cannot  be  easily  attained  in  the  autoclave,  instead  of  using  the  whole 


FIG.  100. 


SACCHARIFICATION 


143 


grain,  it  is  better  to  crush  or  grind  it  coarsely  and  then  to  introduce  it  into  the  necessary 
quantity  of  boiling  water  in  the  autoclave.  During  the  boiling,  the  maize  should  be  kept 
in  continual  motion  by  steam-jets  at  the  bottom  and  along  the  autoclave,  or  by  an  air-jet 
at  the  bottom  with  an  outlet  at  the  top,  so  that  a  spiral  motion  is  imparted  to  the  mass 
(Fig.  107).  Only  rarely  are  mechanical  stirrers  employed  inside  the  autoclave.  After 


FIG.  107. 


FIG.  108. 


an  hour's  heating  the  pressure  reaches  2£  atmos.  and  is  raised  to  3  atmos.  in  another  hour. 
The  mass  is  then  discharged  in  the  usual  way. 

Maize  that  is  too  dry  is  steeped  in  water  for  a  day  before  boiling. 

Maize  always  contains  a  little  ready-formed  sugar  (1-7  to  10  per  cent.),  and  this  must 
be  allowed  for  in  calculating  the  yield  and  also  in  order  to  avoid  too  protracted  heating, 
which  caramelises  the  wort  and  injures  it 
by  decomposing  the  large  proportions  of 
fat  present. 

Saccharification  is  effected  by  means  of 
malt  (2-5  to  3  per  cent,  on  the  weight 
of  maize)  added  to  the  starchy  mass  at  a 
concentration  of  about  14°  Be.  and  cooled 
to  about  50° ;  if  it  is  too  cold,  it  coagulates 
and  the  diastase  acts  irregularly;  at  35° 
to  40°  the  lactic  fermentation  readily  takes 
place;  above  65°  to  70°  the  diastase  is 


FIG.  109. 


FIG.  110. 


altered  and  rendered  less  active,  dextrin  being  then  formed  in  preference  to  maltose.  The 
paste  from  the  Henze  autoclave  is  cooled  in  various  ways,  e.  g.,  with  Ellenberg's  apparatus 
(section,  Fig.  108;  plan,  Fig.  109),  in  which  it  is  dropped  from  the  top  of  a  pipe  into  a 
vessel  similar  to  the  Hollanders  used  in  paper  factories  (see  Paper),  where  it  is  mixed, 
cooled,  and  broken  up  by  a  rotating  drum,  T,  fitted  with  knives  which  graze  other  knives 
fixed  to  an  inclined  plate,  d,  at  the  bottom  of  the  vessel ;  the  drum  makes  200  revolutions 
per  minute;  above  the  pipe,/,  by  which  the  paste  enters  is  a  Korting  injector,  e,  which 
produces  a  strong  current  of  air,  and  thus  facilitates  the  cooling  of  the  paste  during  its  fall. 


144 


At  the  present  time  preference  is  given  to  apparatus  with  centrifugal  stirrers,  the 
cooling"  and  also  the  saccharification  being  carried  out  in  these.  Fig.  110  shows  the 
Hentschel  apparatus.  The  hot  starch-paste  from  the  Henze  converter  passes  through  the 

pipe  b  into  the  vessel  A,  where  it  is  cooled 
by  water  flowing  from  m  to  n  through  an 
internal  coil ;  the  mass  is  mixed  by  means 
of  a  kind  of  screw,  B,  rotated  by  bevel- 
wheels  outside  the  vessel  and  the  air- 
draught  is  produced  by  the  Korting 
injector,  r.  Fig.  Ill  shows  a  section  of 
the  Pauksch  masher,  in  which  the 
cooling  is  effected  by  means  of  water 
circulating  through  the  jacket,  C,  sur- 
rounding the  vessel,  the  liquid  being 
mixed  by  four  blades,  -p,  which  are 
rapidly  rotated  (300  revolutions  per 
minute)  by  the  pulley,  S,  and,  as  they 
graze  the  bottom  of  the  vessel,  have  also 
a  grinding  action.  A  battery  of  Henze 
autoclaves  is  sometimes  used  in  con- 
junction with  one  masher  (Fig.  112). 

Since,    during    this    saccharification, 
which  may  last  three  or  four  hours  (and 
is  complete  when  a  test  of  the  liquid, 
FIG.  111.  now  very  fluid,  no  longer  gives  the  blue 

starch    reaction   with   iodine   solution), 

the  mass  may  become  infected  with  extraneous  bacteria,  which  may  have  a  harmful 
influence  during  the  alcoholic  fermentation  of  the  wort,  it  is  usually  heated  for  a  few 
minutes  at  70°  to  75°  to  kill  these  germs.  This  procedure  has,  however,  the  disadvantage 
of  destroying  the  diastase,  which 
can  always  play  a  part  during 
the  fermentation,  and  of  increas- 
ing the  quantity  of  dextrin. 

In  the  Effront  process  (see 
later),  the  fermentation  is  carried 
out  in  presence  of  hydrofluoric 
acid,  which  kills  all  the  bacteria 
but  not  the  yeast  (previously 
acclimatised  to  the  hydrofluoric 
acid),  so  that  the  saccharification 
may  be  effected  at  the  most 
favourable  temperature  (55°) 
without  subsequently  heating  to 
75°. 

As  soon  as  the  saccharification 
is  terminated,  the  wort  should  be 
cooled  to  about  20°,  and  the 
fermentation  started.  This  cool- 
ing may  be  accomplished  in  the 
masher,  with  suitable  internal 
coolers  (Fig.  110),  but  it  is  better 
done  in  appropriate  apparatus. 

One  form  of  horizontal 
Hentschel  refrigerator  is  shown  jrIG  112. 

in    Fig.     113.      The    horizontal 

rotating  axis  (40  to  50  turns  per  minute)  is  formed  of  a  tube,  to  which  is  fastened  a  deep 
screw  and  in  which  cold  water  circulates  from  h  to  k.  The  screw  moves  in  a  horizontal 
cylinder  through  which  the  hot  wort  is  forced  by  the  screw  in  a  direction  (b  to  /)  opposite 
to  that  taken  by  the  water ;  the  temperature  of  the  wort  at  the  outlet,  /,  is  controlled  by 


FERMENTATION 


145 


regulating  the  flow  of  wort  and  water,  and,  if  necessary,  by  spraying  the  exterior  of  the 
cylinder  with  water  by  means  of  the  tube  I.  With  700  c.c.  of  water,  a  litre  of  wort  is 
cooled  from  60°  to  16°. 

To  separate  the  solid 
residue, husks, etc.  (grains), 
from  the  wort,  the  latter 
is  filtered  cold  through 
dehuskers,  which  have 
different  forms,  some  fixed 
and  some  revolving.  The 
most  recent  Pauksch  type 
consists  of  a  kind  of 
centrifuge  (hydro-extrac- 


FIG.  113. 


tor)  with  a  fine  copper 
gauze  basket,  almost  like 
the  centrifuges  used  in  sugar  factories  (see  Sugar). 

Brewers  and  distillers  often  use  also  the  Hentschel  dehusker  (Figs.  114  and  115),  con- 
sisting simply  of  a  rotating  drum,  with  a  spiral  of  metal  gauze,  which  carries  the  drained 


FIG.  114. 


FIG.  115i 


grains  to  the  middle  and  discharges  it  in  cakes  through  doors  which  close  automatically; 
the  liquid  flows  to  the  bottom  and  passes  to  the  fermenting  vessels. 


(a)  Acetic  bacteria 


(b )  Lactic  bacteria 
FIG.  110. 


ALCOHOLIC    FERMENTATION.     Industrially  the   transformation  of    saccharine 
worts  into  alcoholic  liquors  is  always  effected  by  means  of  organised  ferments  (or  yeasts). 

Worts  left  exposed  to  the  air  at 
15°  to  30°  ferment  spontaneously, 
but,  owing  to  the  different  species 
of  bacteria  present,  not  only 
alcoholic  fermentation,  but  also 
harmful  secondary  fermentations, 
such  as  the  acetic,  lactic,  butyric, 
etc.  (the  corresponding  bacteria 
FIG.  117.  are  shown  in  Fig.  116),  develop. 

Owing  to  the  studies  of  Bees, 

and  more  especially  of  Hansen,  it  is  nowadays  admitted  by  everybody  that  the  principal 

agent  of  alcoholic  fermentation  is  Saccharomyces  cerevisice  (Fig.  117,  a,  b,  and  c),  a  fungus 

VOL.  II.  10 


146 


ORGANIC    CHEMISTRY 


that  multiplies  by  budding  and  has  varying  dimensions  (2-5  to  10  //,)  and  appearance 
according  as  it  develops  at  the  surface  (Fig.  118)  or  in  the  body  of  the  wort  (Fig.  119). 
In  Fig.  120  is  represented  a  cell  of  the  ferment  magnified  4000  times  and  showing  the 
granulations,  vacuoles,  protoplasm,  cell-  wall,  etc.  In  spirit  distilleries,  a  mixture  of  two 
varieties  of  yeast  (top-  and  bottom-yeasts)  is  used,  these  being  of  the  same  race,  but  not 
interconvertible;  often  top-yeast  is  preferred,  as  it  is  more  active,  whilst  in  lager-beer 
breweries,  where  the  fermentation  is  slow,  bottom-yeast  is  mostly  used  (see  later  :  Beer). 

The  final   result   of  the   decomposition  of 
maltose  by  yeast  may  be  expressed  thus  : 


CHO 


H20  =  4C2H5  •  OH 


1222n         2  25  4C02; 

actually,    however,    the    maltose    and    dextrin 
formed  from  the  starch  are   transformed  into 


FIG.  118. 


FIG.  119. 


glucose  by  the  action  of  the  maltase  contained  in  the  ferment  along  with  the  zymase, 
the  latter  then  converting  95  per  cent,  of  the  glucose  into  alcohol  and  carbon  dioxide 
with  development  of  heat  (if  the  glucose  were  transformed  completely  into  H2O  -)-  CO2, 
the  evolution  of  heat  would  be  seven  times  as  great) : 

C6H1206  (glucose)  =  2C2H5  •  OH  +  2C02  +  22,300  cals. 

In  general  ferments  decompose  or  ferment  carbohydrates  containing  in  the  molecule  a 
number  of  carbon  atoms  divisible  by  three,  but  they 
exhibit  a  preference  for  certain  stereoisomerides. 

A  small  part  of  the  sugar  serves  for  the  growth 
and  multiplication  of  the  yeast  (Pasteur),  about 
3  per  cent,  of  it  is  converted  into  glycerol,1  about 
0'5  per  cent,  into  succinic  acid,  and  the  remainder 
into  higher  alcohols  forming  fusel  oil,  this  consisting 
mostly  of  amyl  alcohol  (C5Hn  •  OH,  isobutylcarbinol), 
with  small  proportions  of  isopropyl  alcohol,  butyl 
alcohols,  and  esters.  Ehrlich  (1909)  has  shown, 
however,  that  fusel  oil  and  succinic  acid  are  formed 
by  the  decomposition  of  the  amino-acids  which 
constitute  the  cells  of  the  ferment. 

For  their  nutrition  yeasts,  like  bacteria  (see  p. 
132),  derive  carbon  from  the  sugars  (maltose,  etc.), 
and,  in  some  cases,  even  from  methyl  and  ethyl 
alcohols  (4  per  cent.);  the  nitrogen  may  be  taken 
from  ammonium  salts,  amino-acids,  nitrates,  urea 

or  even  free  ammonia.  Sometimes  yeasts  assimilate  certain  sugars  (e.  g., 
maltose,  melibiose,  raffinose)  without  hydrolysis  being  necessary,  i.  e.,  without 
fermenting  them,  while  sometimes  various  sugars  (e,.  g.,  glucose  and  saccharose) 
are  not  assimilated,  but  are  fermented. 

The  formation  of  glycerol  during  fermentation  has  not  yet  been  explained ;  it  is  thought 
that  it  forms  a  direct  secondary  product  from  the  decomposition  of  the  sugar  into  alcohol  and 
^O2,  or  that  it  results  from  the  action  of  lipase  on  the  fats  and  oils  of  the  ferment  cells ;  Buchner 
(1906)  holds  that  it  is  formed  from  the  sugar,  but  by  a  special  process;  Reisch  (1907),  however, 
finds  no  relation  between  the  amounts  of  alcohol  and  glycerol  formqd,  and  hence  regards  it  not 
as  a  product  of  fermentation,  but  rather  as  a  metabolic  product  ot  the  yeast. 


FIG.  120. 


PURE    YEASTS  147 

The  theoretical  yields  of  pure  alcohol  from  various  sugars  are  as  follow  : 

100  grams  of  saccharose  C12H22On  — 51 '11  grams  or  64'6  c.c.  of  alcohol 

,,  ,,  maltose      Qiz^zzPu  — 51*11         „        64*6     „  ,, 

„  starch         (C6H10O5)»--66-80         „        71'8     „ 

„  glucose         C6H1206   -48-67         „        61  -6     „ 

Various  sugars,  however,  do  not  ferment  directly  (saccharose,  lactose,  etc.), 
but  must  first  be  inverted,  that  is,  transformed  into  hexoses  (fermentable 
sugars  with  six  carbon  atoms),  but  ordinary  alcoholic  ferments  (saccharo- 
mycetes)  contain  the  inverting  enzymes  (besides  zymase),  and  hence  can  effect 
inversion  and  then  fermentation.1 

The  fermentation  industries  in  general,  and  the  alcohol  industry  in  particular,  have 
made  marked  progress  since  the  introduction  of  pure  ferments.  The  cultivation  of  pure 
yeasts  has  at  the  present  time  become  a  special  industry  of  great 
importance;  all  precautions  are  taken  to  select  and  cultivate  well- 
defined  races  of  ferments,  and  this  is  especially  owing  to  Hansen  of 

cL 


Copenhagen,  who,  by  thirty  years  of  study  and  experiment,  showed 

the  great  practical  value  of  the  selection  of  yeasts.     The  first  pure  ~Fia.  121. 

culture  is  made  in  a  moist  chamber  of  glass,  c  (Fig.  121),  fixed  on  a 

microscope  slide,  d ;  the  whole  is  sterilised,  either  by  a  flame  or  by  heating  for  two  hours 

in  an  oven  at  150°.     Sterilised  water  is  placed  on  the  bottom  of  the  chamber  to  keep  the 

atmosphere  moist,  and  the  chamber  placed  in  an  incubator  at  30°  to  35°.     The  yeast 

culture  is  developed  in  a  drop  of  gelatine,  b,  adhering  to  the  lower  side  of  the  cover-glass 

covering  the  chamber. 

The  culture  of  pure  ferments  may  also  be  carried  out  in  Chamberland  flasks  of  30  c.c. 
capacity  (Kg.  122),  half  filled  with  nutrient  gelatine  and  fermentable  substances,  and 
covered  with  a  glass  cap  full  of  sterilised  cotton- wool. 

The  more  or  less  pure  yeast  which  it  is  desired  to  cultivate  is  introduced  by  means 
of  a  sterile  platinum  wire  into  a  flask  containing  sterile  water,  which  is  well  mixed  and 
should  become  just  turbid.  A  drop  of  this  water  is  then  examined  under 
the  microscope  in  order  to  ascertain  the  number  of  yeast  cells  it  contains. 
By  means  of  a  platinum  wire  sterilised  in  a  flame,  a  drop  of  the  water  is 
introduced  into  a  Chamberland  flask  containing  liquefied  gelatine  at  35°. 
After  the  latter  has  been  well  shaken,  a  drop  of  the  gelatine  is  examined 
microscopically  on  a  glass  micrometer  (marked  with  crossed  lines)  to  see 
that  there  are  not  too  many  or  too  few  cells  present,  since  the  colonies 
that  ultimately  develop  from  the  single  cells  should  remain  sufficiently  far 
apart  from  one  another  not  to  mingle.  Of  this  inoculated  gelatine,  one  or 
more  drops  are  placed  on  the  cover-glass  of  the  moist  chamber,  this  being 
FIG.  122.  kept  under  a  bell-jar  until  the  gelatine  has  solidified  and  then  placed, 
upside  down,  on  the  chamber.  In  a  thermostat  at  25°  the  yeasts  are  usually 
sufficiently  developed  after  two  or  three  days,  and  the  various  colonies  are  then  examined 
under  the  microscope  to  ascertain  if  one  or  more  of  them  are  pure,  that  is,  constituted  of 
similar  cells  of  one  and  the  same  yeast.  Each  of  the  pure  colonies  is  touched  separately 
with  a  small  piece  of  sterilised  platinum  wire,  which  is  immediately  dropped  into  a  Pasteur 
flask  (125  c.c. )  charged  to  the  extent  of  two-thirds  with  a  nutritive  solution  (e.  g.,  malt  wort) 
(Fig.  123),  the  rubber  tube  being  momentarily  removed.  The  flask  is  at  once  closed  again, 
and  is  then  kept  in  a  thermostat  at  25°  to  28°.  After  two  days  the  liquid  will  be  in  a  state 
of  active  fermentation,  a  large  quantity  of  the  yeast  having  been  formed.  Each  of  these 
flasks  represents  a  pure  culture  (provided  that  the  proper  precautions  have  been  taken  in 

1  According  to  Boysen-Jensen  (1909)  the  zymase  of  alcoholic  ferments  is  constituted  of 
two  enzymes  :  dextrase  and  dihydroxyacetonase,  glucose  first  forming  2  mols.  of  dihydroxyacetone 
OH  •  CH2  •  CO  •  CH2  •  OH  (triose,  see  p.  136),  which  to  a  small  extent  may  be  fixed  in  the  form 
of  oxime  or  hydrazone  (which  see)  by  means  of  hydroxylamine  hydrochloride  or  methylphenyl- 
hydrazine  acetate ;  the  dihydroxyacetonase  then  decomposing  the  dihydroxyacetone  into  2C02 
and  2C2H5OH.  The  dextrase  alone  would  give  directly  alcohol  and  C02  if  glycerol  were  added 
to  the  solution  of  glucose.  With  zymase  (which  contains  dihydroxyacetonase),  pure  dihydroxy- 
acetone gives  alcohol  and  C02,  whilst  with  oxydases  it  gives  only  C02. 


148 


ORGANIC    CHEMISTRY, 


the  inoculation).     All  the  cultures  are,  however,  examined,  one  or  two  drops  from  each 
flask  being  observed  under  the  microscope. 

These  pure  yeasts  or  other  pure  ferments  are  largely  used  by  brewers  and  distillers,  who 
have  yeasts  suited  to  their  needs  selected  and  preserved  by  scientific  institutions,  from 
which  cultures  in  Pasteur  flasks  are  despatched  to  them  when  the  organisms  in  their  own 
fermenting  vessels  begin  to  degenerate  or  become  contaminated.  In  Fig.  124  is  shown 
diagrammatically  an  apparatus  for  the  industrial  preparation  of  selected  yeast ;  the  metal 
reservoir,  C,  provided  with  a  safety-valve,  q,  and  a  manometer,  r,  is  filled,  by  means  of  the 
pump,  u,  with  air  filtered  through  a  cotton-wool  filter,  t,  and  compressed  under  a  pressure 
of  3  to  4  atmos.  The  vessel,  A,  is  first  sterilised  with  steam  under  pressure,  which  enters 
at  the  tap,/,  whilst  the  air  is  driven  out  through  the  tube  6,  dipping  into  a  vessel  of  mercury 
forming  a  seal.  When  the  cock,  /,  is  shut,  g  is  opened  so  as  to  allow  air  to  filter  through 
d  into  A.  Hot  wort  is  introduced  into  the  reservoir,  A,  heated  to  boiling  and  then  cooled 
by  means  of  a  water-spray  issuing  from  an  annular  tube,  e,  and  bathing  the  outside  of 
A.  The  fermenting  Vessel,  B,  which  is  sterilised  in  the  same  way  as  A,  is  also  furnished 
with  a  cotton- wool  filter,  h,  and  a  hydraulically  sealed  tube,  i  p,  through  which  the  C02 
is  to  escape;  the  glass  tube,  0,  which  is  a  continuation  of  the  filter,  indicates  the  level 
of  the  liquid  inside  the  vessel.  It  is  further  provided  with  a  vertical  stirrer  which  is  set 
in  motion  by  the  handle,  k,  and  serves  to  mix  the  wort  and  yeast  which  are  introduced 


FIG.  123. 


FIG.  124. 


through  the  small  tap,  I.  A  slight  air-pressure  is  maintained  in  both  A  and  B  in  order  to 
prevent  external  contaminated  air  from  entering  either  when  the  discharge-cock,  m,  for 
the  fermented  wort  is  opened  or  through  any  leaks  there  may  be  in  the  apparatus.  In 
this  way  B  may  be  used  for  a  year  or  more  without  contamination  taking  place,  a  little 
residual  yeast  being  left  after  each  operation  to  ferment  the  succeeding  charge  of  wort. 
The  sterile  wort,  cooled  to  15°,  is  passed  from  A  into  B  by  means  of  the  tube  a  n,  and 
before  it  reaches  the  level  of  the  tap,  I,  the  pure  yeast  contained  in  a  Pasteur  flask  is  intro- 
duced through  this  tap ;  B  is  filled  to  the  extent  of  about  three-fourths  (about  200  litres ) 
with  the  wort  from  A,  the  whole  being  then  well  mixed.  When  the  fermentation  is  ended 
(in  three  or  four  days  with  worts  for  alcohol  production,  or  in  eight  to  ten  days  for  beer 
worts),  the  yeast  is  allowed  to  settle ;  the  fermented  wort  is  discharged  from  m  by  increasing 
the  pressure  of  the  air  and,  when  it  begins  to  issue  turbid  (owing  to  suspended  yeast),  m 
is  closed  and  about  30  litres  of  wort  introduced  from  A  and  well  mixed  in,  30  litres  of  the 
turbid  yeasty  liquid  being  then  run  off  from  B,  this  amount  being  sufficient  to  induce  fer- 
mentation in  40  hectolitres  of  wort  in  the  ordinary  fermenting  vessels ;  a  further  quantity  of 
30  litres  of  wort  is  then  run  in  from  A  and,  after  mixing,  another  30  litres  of  yeasty  wort 
drawn  off.  That  remaining  in  B  serves  for  the  next  operation.  This  is  the  procedure 
adopted  in  large  breweries  and  distilleries,  whilst  in  yeast-factories  the  wort  is  prepared 
from  barley  and  rye  under  the  action  of  malt  for  an  hour  at  60°  and  for  about  twenty-four 
hours  at  40°  to  44°,  in  order  to  produce  about  1  per  cent,  of  lactic  acid,  which  peptonises 
the  proteins  and  so  affords  better  nutriment  for  the  yeast,  the  action  being  completed  by 


YEAST    INDUS  TRY  149 

the  addition  of  10  grams  of  sodium  or  ammonium  phosphate  per  hectolitre  of  wort.  The 
wort  is  then  fermented  as  above  at  18°  to  20°,  and  the  yeast,  which  is  formed  in  large 
quantity,  is  washed  with  water  by  decantation,  freed  from  excess  of  water  in  centrifuges 
or  filter- presses,  and  made  into  a  paste  with  5  to  10  per  cent,  of  potato-starch,  forming 
cakes  which  are  sold  under  the  name  of  pressed  yeast.  100  kilos  of  rye  yield  16  kilos  of 
yeast.1 

1  Yeast  Industry.  In  Germany  more  than  21,000  tons  of  yeast  were  made  in  1910,  from 
1000  to  1300  tons  being  exported  annually ;  in  five  factories  alone  over  11,000  tons  were  produced 
in  1909.  In  1912  the  output  reached  43,000  tons. 

Italy  imported  the  following  quantities  of  yeast : 

1905      1908      1910     1912      1913      1914     1915     1916 

Tons          .          .          .136          292  362          582          569          210         30  9-7 

Value  (£)  .          .  18,080     20,940     20,495       7,564      1,080 

Certain  of  the  French  factories  export  as  much  as  three  or  four  tons  of  pressed  yeast  per  day. 
In  Austria,  the  law  of  May  18,  1910,  regulates  the  trade  in,  yeast  so  as  to  prevent  adulteration 
and  mixture. 

In  October  1912,  the  syndicate  of  German  yeast  manufacturers  decided  to  lower  the  price 
by  twopence  per  kilo  (to  about  lOd.  per  kilo),  owing  to  the  lower  prices  of  the  raw  materials 
(barley,  rye,  etc.)  in  the  world's  markets,  and  with  the  view  of  preventing  development  of  the 
works  outside  the  syndicate.  Formerly  the  addition  of  20  per  cent,  of  starch  to  the  yeast 
was  allowed  (if  declared),  but  such  addition  is  now  prohibited. 

Yeast  is  used  (after  repeated  washing  to  remove  bitter  substances,  and  subsequent  drying) 
as  a  concentrated  food  for  invalids  (marmile)  and  as  concentrated  fodder  for  cattle  (removal 
of  the  bitter  matter  then  unnecessary ).  With  hens  and  geese  it  has  given  results  as  good  as  those 
obtained  with  meat  powder  (in  increasing  the  output  of  eggs).  As  human  food  it  serves  to 
replace  plasmon  and  somatose  (as  it  contains  2  per  cent,  of  lecithin);  it  is  used  also  in  the 
treatment  of  boils,  etc.  Its  nutritive  properties  are  due  to  its  highly  assimilable  protein  sub- 
stances, these  in  somatose  costing  more  than  £4  per  kilo.  In  the  moist  state  it  contains  75  to 
80  per  cent,  of  water,  but  with  care  it  may  be  dried  without  loss  in  nutrient  quality ;  a  sample  of 
such  dried  yeast  showed  on  analysis  the  percentage  composition:  water,  1-5  to  3;  ash,  8; 
crude  protein,  54;  cellulose,  1-5;  non -nitrogenous  extractives,  29;  lecithin,  2-2.  To  obtain 
dry  yeast,  the  yeast  may  be  suspended  in  water  and  air  passed  through  the  latter  for  seventy -two 
hours,  the  protein  matters  being  thus  modified  so  that  they  withstand  gradual  drying ;  another 
process  consists  in  mixing  sugar  with  the  pressed  yeast  and  drying  at  50°. 

In  Germany  until  1912  there  was  a  large  excess  of  yeast  not  utilised.  If  the  waste  yeast 
from  all  the  fermentation  industries  were  collected,  it  would  amount  to  about  70,000  tons  per 
annum  (in  Germany).  If,  however,  all  the  pressed  yeast  were  used  as  concentrated  fodder,  the 
output  would  be  insufficient.  The  yeast  distillery  of  Delft  (Holland)  produced  more  than 
7500  tons  of  yeast  and  200,000  hectolitres  of  alcohol  in  1912.  The  largest  consumers  of  pressed 
yeast  are  the  bakers. 

At  one  time,  with  a  yield  of  30  to  32  per  cent,  of  alcohol  on  the  weight  of  cereal  used,  the 
amount  of  yeast  obtained  was  12  to  14  per  cent.  During  recent  years  a  marked  increase  has 
been  effected  in  the  quantity  of  yeast  (up  to  20  per  cent. ),  the  yield  of  alcohol  being  diminished 
by  vigorous  aeration  of  the  wort  during  fermentation  (30  to  40  cu.  metres  of  air  per  hour  for  every 
100  kilos  of  cereals  converted  into  wort).  By  the  new  Braasch  process  the  yield  of  yeast  may  be 
raised  to  40  per  cent,  and  that  of  ajcohol  lowered  to  15  per  cent,  (under  some  conditions  of  the 
market  the  production  of  yeast  is  more  remunerative  than  that  of  alcohol).  The  value  of  yeast 
in  Germany  is  calculated  at  about  £38  to  £40  per  ton,  and  some  factories  produce  as  much  as 
500  to  1000  tons  per  annum ;  the  alcohol  is  valued  at  £1  Ss.  per  hectolitre. 

In  the  old  Vienna  process,  worts  of  10°  to  20°  Balling  (or  even  heavier)  were  fermented  by 
means  of  yeasts  prepared  with  worts  rich  in  lactic  acid  (100  c.c.  of  this  wort  should  require 
12  to  14  c.c.  of  normal  sodium  hydroxide  solution  for  neutralisation).  When  the  fermentation 
was  complete,  the  yeast  was  collected  by  means  of  ladles  and  despatched  along  channels  into 
vats,  where  its  activity  was  arrested  with  cold  water.  After  this,  it  was  shaken  on  silk  sieves, 
which  retained  all  the  husks  or  grains ;  the  yeast  passing  through  the  sieves  was  washed  two 
or  three  times  with  water  and,  after  settling,  pressed  into  cakes.  In  1887-1890  all  yeast  factories 
worked  on  this  plan,  but  nowadays  only  few  of  them  do  so. 

The  new  Braasch  aeration  process  starts  from  clear  wort  and  green  malt  (non-kilned ).  The 
cereals  for  preparing  the  mash  and  thus  the  wort  are  no  longer  ground,  but  are  softened  with 
water  and  then  crushed.  The  mashing  of  the  green  malt  is  carried  out  in  a  medium  slightly 
acidified  with  sulphuric  acid,  the  lactic  ferment  (Bacillus  Delbruckii)  being  allowed  to  act,  after 
the  diastase,  for  several  hours  at  40°  to  50°.  When  the  desired  acidity  is  reached,  further 
acidification  is  prevented  by  heating  the  whole  mass  to  68°  to  70°  (the  total  amount  of  sulphuric 
and  lactic  acids,  without  C02,  corresponds  with  5  c.c.  of  normal  NaOH  per  100  c.c.  of  wort). 
The  concentration  of  the  wort  used  was  at  one  time  12°  to  14°  Balling,  but  at  the  present  time 
10°  Balling  is  preferred.  The  temperature  of  fermentation  is  about  25°.  If  the  acidity  of  the 
wort  is  less  than  2  c.c.  of  normal  soda  per  100  c.c.,  the  yeast  obtained  is  flocculent  and  separates 
badly.  The  separation  of  the  yeast  is  now  effected  thoroughly  and  rapidly  in  centrifuges.  The 
fermentation  is  started  by  adding  to  the  wort  4  to  5  per  cent,  of  yeast  (calculated  on  the  weight 


150 


ORGANIC    CHEMISTRY 


In  France,  and  latterly  in  Italy,  industrial  spirit  distillers  are  making  use  of  the  Jacque- 
min  apparatus  (Fig.  125)  for  the  preparation  of  pure  yeast  cultures.  The  peptonised 
wort  is  prepared  as  described  above,  and  the  sterilised  air,  compressed  by  the  pump  A, 
passes  through  a  filter  of  cotton  wool  moistened  with  mercuric  chloride,  F,  into  a  battery 
of  vessels,  G,  the  first  and  third  of  which  are  empty,  whilst  S  contains  sulphuric  acid  and 
n  soda  solution ;  the  empty  vessels  serve  as  safeguards,  in  case  the  liquids  are  sucked 
backwards.  The  air  sterilised  in  this  way  passes  along  suitable  pipes  to  all  the  fermenting 
vessels,  B,  B',  C,  C',  D.  B  is  two-thirds  filled  with  the  peptonised  wort  (20  to  30  litres), 
which  is  boiled  for  a  few  minutes  by  steam  entering  through  b  and  then  cooled  by  passing 
a  vigorous  current  of  air  through  the  wort  and  by  an  annular  spray  of  water  applied  to  the 
outside  of  the  vessel  B  by  the  tube  e.  When  the  temperature  has  fallen  to  20°,  the  con- 
tents of  a  Pasteur  flask  of  pure  yeast  are  introduced  through  the  tube  a,  and  the  fermenta- 
tion allowed  to  proceed  for  twenty -four  hours ;  in  the  meantime,  wort  sterilised  and  cooled 
to  20°  is  prepared  in  B' ;  a  little  of  the  yeast  is  then  passed  from  B  through  the  tube  t  to 
B',  the  remainder  being  discharged,  by  the  three-way  cock,  t,  into  the  larger  vessel,  C, 

which  contains  sterilised  wort  (250 
to  300  litres).  When  the  fermen- 
tation has  reached  an  advanced 
stage  (a  definite  attenuation :  see 
later),  the  wort  is  discharged 
through  the  tube  r  into  D,  which 
also  contains  sterilised  wort,  and 
that  remaining  on  the  bottom  of 
C  is  forced  by  compressed  air  into 
the  vessel  C",  previously  charged 
with  sterile  wort. 

It  will  be  seen  that,  by  this 
procedure,  the  working  is  continu- 
ous, and  the  yeast  is  renewed 
only  once  or  twice  per  month. 
The  yeast  may  then  be  separated 
from  D  and  pressed,  or  the  actively 
fermenting  wort  (5  to  6  hectolitres) 
may  be  used  to  induce  fermentation 
in  the  factory  vats  containing 
ordinary  wort. 

The  selected  yeasts  are  con- 
trolled practically,  by  measuring 
their  fermentative  activity  and 
by  determining  the  concentra- 
tion with  the  microscope  and 
cell-counters,  note  being  taken  of  extraneous  organisms. 

Pressed  yeast  in  cakes  keeps  for  several  days  if  well  wrapped  in  paper  and  placed  in 
tightly  closed  boxes  in  a  cool  room ;  otherwise  it  soon  becomes  covered  with  mould  and 
unusable.  When  the  stock  of  yeast  is  larger  than  is  required,  it  may  be  dried  at  a  cost 
of  10s.  per  ton  and  sold  as  a  good  cattle  food.  To  prevent  secondary  fermentations  from 
taking  place,  instead  of  the  lactic  acid  fermentation,  during  the  preparation  of  selected 
yeasts,  Biicheler  (Ger.  Pat.  123,437)  suggests  the  addition  of  180  c.c.  of  concentrated 

of  cereals  used )  and  is  finished  in  ten  to  twelve  hours ;  the  yield  of  40  per  cent,  (on  the  weight  of 
cereals)  of  yeast  is  in  addition  to  the  amount  added  (5  per  cent.).  The  yeast  cultures  should  be 
renewed  occasionally. 

The  fermented  wort  is  feebly  alcoholic  (less  than  1  per  cent,  of  alcohol),  so  that  the  distillation 
and  rectification  necessary  to  obtain  90  to  95  per  cent,  alcohol  are  very  expensive;  further, 
the  alcohol  is  not  of  good  quality  and  is  hence  only  suitable  for  denaturing.  The  diminished 
yield  of  alcohol  is  due  partly  to  loss  of  the  alcohol  carried  away  by  the  large  volumes  of  air  passed 
through  the  wort,  and  partly  to  destruction  of  maltose  by  ferments  or  enzymes  developing  in 
presence  of  excess  of  air.  The  less  the  amount  of  air  used,  the  greater  is  the  amount  of  spirit 
obtained. 

In  the  control  of  the  purity  of  the  yeast,  account  must  be  taken  of  the  extraneous  ferments, 
of  the  quantity  of  starchy  substances  (when  starch  is  not  added  this  does  not  reach  4  per  cent. ), 
and  of  the  fermentative  activity. 


FIG.  125. 


ANTISEPTICS  151 

sulphuric  acid  to  every  hectolitre  of  wort;  the  process  yields  excellent  results  in  practice, 
notwithstanding  the  disputing  of  the  patent  from  1900  to  1909,  owing  to  the  fact  that  a 
similar  patent  (No.  3885)  was  granted  in  Austria  to  Bauer  in  1900. 

FACTORS  WHICH  FACILITATE  OR  RETARD  FERMENTATION.  Alcoholic 
fermentation  may  be  hindered,  by  various  factors.  Very  concentrated  sugar  solutions 
do  not  ferment,  whilst  with  a  concentration  of  70  per  cent.,  only  6  per  cent,  of  the  sugar 
is  converted  into  alcohol;  with  a  strength  of  60  per  cent.,  25  per  cent,  is  transformed, 
and  when  the  concentration  is  30  per  cent,  it  is  possible,  although  not  without  difficulty, 
to  convert  92  per  cent,  of  the  sugar  into ,  alcohol. 

•Temperature  has  also  a  very  marked  influence  on  alcoholic  fermentation,  which  at  0° 
or  at  60°  ceases  completely;  later  we  shall  see  at  what  temperature  the  process  takes 
place  most  regularly  from  the  point  of  view  of  the  industrial  yield. 

Alcohol,  although  a  product  of  fermentation,  when  it  reaches  a  certain  concentration, 
may  prevent  further  fermentation.  This  anti-fermentative  action  of  the  alcohols  is, 
to  some  extent,  proportional  to  their  molecular  weights.  Thus  the  fermentation  of  glucose 
may  be  arrested  by  20  per  cent,  of  methyl  alcohol,  16  per  cent,  of  ethyl  alcohol,  10  per  cent, 
of  propyl  alcohol,  2-5  per  cent,  of  butyl  alcohol,  1  per  cent,  of  amyl  alcohol,  and  0-1  per 
cent,  of  capryl  alcohol. 

ANTISEPTICS,  in  general,  prevent  fermentation  when  they  are  present  in  relatively 
high  concentrations;  they  may,  if  their  dilution  is  great,  exert  a  favourable  influence 
on  fermentation.1 

However,  since  the  favourable  action  exhibited  by  these  solutions  depends  on  the 
quantity  of  yeast  present  and  that  of  the  antiseptic  dissolved,  it  is  possible,  when  the 
quantity  of  yeast  is  large,  that  solutions  more  concentrated  than  those  indicated  in 
column  (B)  may  produce  favourable  effects  on  the  fermentation.  It  is  unnecessary  to 
state  that  these  concentrations  vary  somewhat  with  the  nature  of  the  organisms.  It 
has  been  shown  recently  (1910),  for  example,  that  Staphylococcus  pyogenes  aureus  resists 
a  2-7  per  cent,  solution  of  mercuric  chloride  for  six  hours. 

The  organic  acids  also  exert  an  unfavourable  influence  on  alcoholic  fermentation,2 
whilst,  within  certain  limits,  lactic  and  formic  acids  and  formaldehyde  have  a  beneficial 
action,  since  they  prevent  the  development  of  harmful  bacteria  and  are  readily  tolerated 
by  alcoholic  ferments  specially  acclimatised  to  their  action.  By  adding  small  quantities 
of  formaldehyde  and  of  sterilised  milk  (which  then  gives  lactic  acid),  the  yield  of 
alcohol  has  recently  been  increased  by  as  much  as  2  per  cent.  E.  Soncini  (1910)  has 
shown  that  the  course  of  fermentation  in  general  is  closely  connected  with  the  chemical 
medium  in  which  it  takes  place;  thus,  in  a  saccharine  wort  (from  bananas),  the  lactic 
fermentation  first  develops  spontaneously  and  proceeds  until  the  lactic  acidity  reaches  a 
certain  limiting  amount;  this  may  be  followed  by  alcoholic  fermentation,  which,  in  its 
turn,  may  be  succeeded  by  the  acetic  fermentation;  the  lactic  fermentation  may  ulti- 
mately begin  again.  It  is  only  by  considering  all  these  conditions  that  a  regular  alcoholic 
fermentation  and  a  good  yield  of  pure  alcohol  may  be  assured,  since  in  general  the  secondary 

1  Thus,  for  example  : 

(A)  The  most  dilute  solution'  (B)  The  most  concentrated 
capable  of  preventing  solution  capable  of 

fermentation  is :  favouring  fermentation  is  : 

Mercuric  chloride    ...  1  in  20,000  1  in  300,000 

Potassium  permanganate          .  10,000  100,000 


Bromine 
Thymol 
Salicylic  acid 
Phenol 

Sulphuric  acid 
Boric  acid 


4,000 
3,000 
1,000 
200 
100 
25 


50,000 

20,000 

6,000 

1,000 

10,000 

8,000 


2  The  action  of  some  of  the  commoner  acids  is  as  follows  : 


Dose  that  retards  Dose  that  arrests 

alcoholic  fermentation  alcoholic  fermentation 

Acetic  acid     ....                      0-50%  1-  0% 

Formic  „                                                           0-20%  0-30% 

Propionic  acid         .         .          .   -                   0-15%  0-30% 

Valeric         „                                                     0-10%  0-15% 

Butyric        „            .          .          .                       0-05%  0-10% 

Caproic        „           .          ,          ,  0-05% 


152  ORGANIC    CHEMISTRY 

and  harmful  products  of  the  fermentation  (higher  alcohols,  such  as  amyl,  etc.)  result 
from  the  actions  of  extraneous  micro-organisms.  The  carbon  dioxide  formed  during 
fermentation  may  give  rise  to  pressures  as  high  as  12  atmos.  if  hermetically  sealed  vessels 
are  used,  and  the  action  of  the  yeast  is  then  retarded  or  even  arrested. 

PRACTICE  OF  FERMENTATION.  To  start  the  fermentation  of  the  worts  pre- 
pared as  described  above,  various  methods  are  used  :  in  some  cases  a  portion  of  old, 
fermented  wort  from  a  preceding  operation  is  employed,  but  this  is  not  a  rational  method, 
because  the  yeast  in  the  old  wort  is  in  a  condition  unfavourable  to  development  and  is 
also  contaminated  with  other  micro-organisms  which  would  develop  readily  in  the  new 
wort.  To  be  preferred  is  the  custom  followed  by  certain  distilleries  of  starting  the  fer- 
mentation with  brewery  yeast,  which  is  cheap  and  comparatively  pure.  The  best  and 
most  rational  method  is,  however,  the  use  of  selected  yeast  in  culture  wort  or  in  a  pressed 
condition  (see  above),  as  supplied  by  various  firms  and  institutions  which  guarantee  its 
purity.  By  this  means  alone  it  has  been  possible  during  the  past  few  years  to  increase 
the  mean  yield  of  alcohol  in  distilleries  by  0-5  per  cent,  or  even  1  per  cent.,  and  at  the 
same  time  to  improve  the  quality  of  the  product. 

It  is  advisable  to  ferment  worts  as  soon  as  they  are  prepared  and  cooled  to  15°  to  20°, 
delay  resulting  in  contamination  with  heterogeneous  germs  always  present  in  the  air. 

To  avoid  secondary  fermentations  as  far  as  is  possible,  addition  is  often  made  to  the 
wort  of  antiseptics,  to  which  the  selected  yeasts  have  been  habituated.  Thus,  small 
proportions  of  calcium  bisulphite  or,  better,  of  ammonium  or  aluminium  fluoride  are 
added,  the  hydrofluoric  acid — liberated  under  the  action  of  the  acids  formed  in  the 

secondary  fermentations — killing  the 
harmful  organisms.  With  the  Eff  ront 
process,  hydrofluoric  acid  (see  Vol.  I., 
p.  167)  is  added  directly  in  the  pro- 
portion of  5  or  even  10  grams  per 
hectolitre  of  wort  (some  yeasts  resist 
as  much  as  100  grams  of  HF  per 
FIG.  126.  hectolitre).  Sometimes  a  selected 

lactic   ferment    (Bacillus   acidificans 
longissimus)  is  added,  this  also  favouring  the  production  of  pure  alcohol. 

The  use  of  these  yeasts  acclimatised  to  the  action  of  hydrofluoric  acid  renders  possible 
the  employment  of  the  temperature  55°  to  57°  (see  above)  for  the  previous  saccharification 
of  the  starch  by  diastase,  this  low  temperature  resulting  in  the  formation  of  an  increased 
amount  of  maltose;  also  if  there  are  other  noxious  living  micro-organisms  in  the  wort, 
these  are  killed  by  the  hydrofluoric  acid  during  the  fermentation. 

Effront,  however,  succeeded  in  preparing  yeasts  capable  of  fermenting  with  ease  also 
the  dextrin ;  when  these  are  used,  the  saccharification  with  diastase  may  be  effected  with 
less  malt  and  at  64°  to  65°,  so  that  harmful  micro-organisms  are  killed.  All  the  apparatus, 
instruments,  and  vats  which  come  into  contact  with  the  wort  should  be  previously  washed 
with  dilute  hydrofluoric  acid  solution  (100  grams  per  25  litres  of  water). 

For  every  hectolitre  of  wort  are  added  about  30  grams  of  pressed  yeast  in  small  quantities 
mixed  with  increasing  quantities  of  wort  and  well  stirred  in;  the  fermentation  then 
starts  immediately. 

The  fermentation  of  the  wort  proceeds  in  three  successive  phases  : 

(1)  Preliminary  fermentation,   in   which   the   yeast   develops    and   grows, 
the  most  favourable  temperature  being  17°  to  21°. 

(2)  Principal  fermentation,  in  which  the  maltose  and  glucose  are  fermented, 
best  at  26°  to  30°. 

(3)  Secondary    fermentation,   in   which   the   dextrins   are   fermented,   the 
diastase  continuing  to  saccharify  the  remaining  dextrins  as  the  wort  becomes 
warm,  the  best  temperature  being  25°  to  27°. 

The  vats,  holding  10  to  90  hectolitres,  and  often  furnished  with  stirrers,  are  filled  with 
wort  to  the  extent  of  nine-tenths.  The  temperature  is  regulated  by  suitable  cold-water 
coils  (attemperators,  Fig.  126),  which  are  of  various  forms  (see  Beer).  In  general,  these 
attemperators  have  a  surface  of  0-3  to  0-4  sq.  metre  per  10  hectolitres  of  wort.  Fermentation 


YIELD    OF    ALCOHOL  153 

is  begun  in  the  vats  at  12°  to  15°,  and  after  two  or  three  hours  the  temperature  rises  and 
the  fermentation  becomes  vigorous.  The  liquid  is  then  agitated  to  liberate  the  CO2,  thus 
diminishing  the  pressure  in  the  mass  and  facilitating  the  fermentation,  the  temperature 
not  being  allowed  to  exceed  28°  to  29°.  After  two  days,  the  principal  fermentation  ceases 
and  the  temperature  is  maintained  at  25°  to  26°  for  a  day,  the  fermentation  being  thus 
completed. 

Worts  that  are  too  dilute  or  are  made  from  poor  malt  or  impure  grain  give  a  boiling 
fermentation  that  hurls  the  liquid  from  the  vat  and  renders  the  subsequent  distillation 
difficult.  This  inconvenience  is  avoided  by  using  more  concentrated  worts  and  good 
yeast,  or,  in  case  of  necessity,  adding  100  to  200  c.c.  of  oil  to  each  vat. 

Ammonium  fluoride  (2  to  25  grams  per  hectolitre)  or  hydrofluoric  acid  (rather  less)  is 
often  added  to  the  wort  before  fermentation. 

In  some  modern  distilleries  covered  fermenting  vats  or  wash  backs  are  used,  these  giving 
good  results  also  in  beer  brewing  (q.  v. ).  By  this  means  the  CO2  may  be  utilised,  while  the 
yield  of  alcohol  is  increased  by  2  to  3  per  cent.,  that  carried  away  by  the  C02  being  recovered 
from  the  wash  liquors  of  the  gas. 

LOSSES  AND  YIELDS.  A  residue  of  unfermented  starch  (0-7  to  2  per  cent.)  and 
dextrin  (5  to  8  per  cent. )  always  remains  after  fermentation.  In  every  fermentation  2  to 
3  per  cent,  of  glycerol  is  formed;  also  part  of  the  sugar  serves  as  food  for  the  yeast  and 
part  of  the  alcohol  evaporates,  this  making  a  total  loss  of  6  to  8  per  cent. 

Starting  with  100  parts  of  starch,  12  to  20  parts  are  usually  lost  in  various  ways,  while 
with  improper  working  the  loss  may  reach  28.  per  cent. 

If  the  starch  could  be  transformed  theoretically  into  alcohol  and  carbon  dioxide  alone, 
100  kilos  of  starch  should  yield  71-6  litres  of  pure  alcohol;  allowing  for  these  losses  and 
working  under  the  best  conditions,  63-5  litres  of  alcohol  are  obtained ;  60  litres  is  a  good 
yield  and  58  litres  a  medium  one,  whilst  55  litres  would  indicate  bad  conditions  of  working. 
The  mean  starch-contents  of  many  of  the  prime  materials  used  in  the  distillery  are  given" 
on  p.  141 ;  that  of  green  malt  (from  good  barley)  is  38  to  42  per  cent.,  and  that  of  kilned 
malt,  65  to  70  per  cent.  Whilst  in  1883  Italian  distilleries  gave  an  average  yield  of  315  litres 
of  alcohol  per  ton  of  maize,  in  the  season  of  1904-1905  the  yield  (official  statistics) 
amounted  to  340  litres,  and  now  about  355  litres  is  obtained.1 

For  calculating  the  yield)  the  exact  analyses  of  the  prime  materials,  starch  and  sugar, 
must  be  known.  The  sugar-content  of  a  wort  is  determined  from  the  density  by  means 
of  the  Balling  saccharometer  modified  by  Brix,  degrees  Brix  (or  Balling)  read  at  20° 
(formerly  17-5°)  indicating  directly  the  percentage  of  sugar  in  the  solution.  In  worts, 
however,  part  of  this  density  is  due  to  unfermentable  substances. 

As  fermentation  proceeds,  the  proportion  of  alcohol  increases  and  the  density 
diminishes;  this  diminution  is  called  the  degree  of  fermentation  or  attenuation.  The 
density  is  measured  before,  during,  and  after  the  fermentation  on  the  filtered  wort,  and 
if  it  filters  badly  it  is  diluted  with  a  definite  volume  of  water.2  When  the  fermentation 

1  From  90  kilos  of  maize  and  10  kilos  of  malt,  36  litres  of  pure  alcohol  may  be  obtained, 
and  from  100  kilos  of  potatoes  (with  18  per  cent,  of  starch)  and  1-8  kilos  of  malt,  12  litres.     If 
the  maize  costs  £8  per  ton  (1000  kilos)  and  the  potatoes  £2  4s.,  it  is  advantageous  to  use  maize, 
in  spite  of  the  fact  that  120  kilos  of  coal  are  consumed  per  100  litres  of  alcohol  from  potatoes 
and  150  kilos  in  the  case  of  maize.     The  maize  residues  (grains)  are  worth  almost  three  times 
(about  13s.  per  hectolitre  of  alcohol)  as  much  as  the  corresponding  quantity  from  potatoes. 
The  cost  of  labour,  lubricants,  antiseptics,  etc.,  was  estimated  in  Germany  before  the  War  to 
be  2s.  per  hectolitre  of  alcohol. 

2  The  density,  p,  before  fermentation  is  due  to  x  parts  of  sugars  -f-  z  parts  of  non-fermentable 
substances ;  if  the  density  after  fermentation  indicates  the  magnitude,  z,  then  p  —  z  =  x.     This 
does  not  give  the  absolute  attenuation,  since  z  is  altered  by  the  presence  of  alcohol  and  carbon 
dioxide.     If  the  carbon  dioxide  is  eliminated  by  shaking  and  gentle  heating,  a  density,  m,  is 
obtained  and  the  magnitude  of  (p — m)  gives  the  so-called  apparent  attenuation  (apparent  because 
alcohol  is  still  present ) ;  the  amount  of  alcohol  formed  may  be  allowed  for  by  mean's  of  a  known 
factor,  a,  the  real  attenuation  being  given  by  A  =  a(p — TO).     The  value  of  a  is  determined  by 
distilling. a  small  quantity  of  fermenting  wort,  and  calculating  the  value  of    the    expression 

a  —  .„—,.;  a  is,  however,  not  a  constant,  but  varies  with  the  nature  of  the  sugars,  with  the 

original  concentration,  p,  and  with  the  stage  of  the  fermentation  (incipient,  vigorous,  or  secon- 
dary). If  a  is  known,  the  quantity  of  alcohol  obtainable  from  a  fermented  wort  of  a  given 
density  may  be  calculated. 

The  ratio  between  the  apparent  attenuation  (p — TO)  and  the  original  saccharometer  reading, 
p,  gives  the  so-called  degree  of  apparent  fermentation  (B).  If  p  =  25°  and  the  density  (TO)  of 


154 


ORGANIC    CHEMISTRY 


is  finished  and  the  degree  of  attenuation  controlled,  the  resultant  fermented  wash  (with 
about  9  to  11  per  cent,  of  alcohol)  is  subjected  to  distillation  and  rectification  in  order  to 


the  fermented  wort  is  3,  we  have  B  = 


25-3 
25 


=  0-880,  which  is  the  degree  of  apparent  fermenta- 


tion, and  indicates  that,  of  every  unit  of  saccharine  substances,  0-880  part  have  disappeared, 
i.  e.,  have  been  fermented.     From  the  degree  of  apparent  fermentation  (B),  the  degree  of  apparent 


attenuation  may,  of  course,  be  obtained  :  thus, 


p — m 
P 


=  B  gives  p — m  =  Bp;  and  from  the 
of    apparent 


factor  a  mentioned  above,  the  amount  of    alcohol  resulting    from  such  degree 
fermentation  is  known. 

The  real  attenuation  (A')  is  determined  by  distilling  a  certain  quantity  of  the  fermented  wort 
until  its  volume  is  reduced  to  one-third,  the  residue  being  made  up  to  the  original  volume  with 
water  and  the  density,  n,  measured;  the  real  attenuation  then  =  p — n.  Since,  however,  the 
residue  always  contains  unfermented  matter,  in  order  to  calculate  the  alcohol,  a  factor,  b,  is 
determined  in  the  same  way  as  the  factor  a,  i.  e.,  by  distillation  of  a  part  of  the  fermented  wort ; 
the  quantity  of  alcohol  can  then  always  be  determined  from  the  density  of  the  fermented  wort, 

for,  since  A'  =  (p — n)  b,  b  =    -  — ,     Similarly,  the  degree  of  real  fermentation  will  be  B'  =  -SC-— ', 

which  expresses  the  fraction  of  the  extract  (dissolved  substance  without  alcohol)  really  fermented, 
the  manufacturer  being  thereby  able  to  judge  if  the  fermentation  proceeds  normally  and  to 
establish  comparisons  with  previous  fermentations,  etc. 

The  apparent  attenuation  (alcohol  being  present)  is  always  greater  than  the  real  (derived 
after  elimination  of  the  alcohol),  and  the  attenuation  difference,  D,  is  obtained  by  subtracting  one 
from  the  other,  (p — TO) — (p — n)  —  D.  This  magnitude,  D,  is  therefore  equal  to  n — m  and 
increases  as  the  fermentation  proceeds  towards  completion;  also  here  the  quantity  of  alcohol 
already  formed  is  found  by  determining  experimentally  a  factor,  c,  in  the  usual  way,  so  that 


A 


The  ratio  of  the  apparent  to  the  real  attenuation,   "         =  q, 


=  c,  or  A  =  (n — m)c. 
n — m  '  p — n 

gives  a  quotient  of  attenuation  which  varies  with  the  concentration  of  the  liquid  but  becomes 
constant  towards  the  end  of  the  fermentation  and  shows  how  much  the  apparent  fermentation 
"is  greater  than  the  real ;  by  its  means,  almost  all  the  saccharometric  calculations  may  be  made  : 

=  the  alcohol  factor  for  the  real  attenuation,  and  if  this  is  divided  by  q  diminished  by  unity 


TABLE  FOR  CALCULATING  THE  ATTENUATION  IN  FERMENTED  WORTS 


Alcohol  factors  for  the 

Saccharometer 
degrees  of  the  wort 

attenuation 

Factors  for  the 
attenuation 
differences 

Attenuation 
quotient 

Apparent 

Eeal 

Values  of  c- 
b 

P 

a 

b 

c 

} 

6    . 

0-4073 

0-4993 

2-2095 

1-226 

4-4247 

7    . 

0-4091 

0-5020 

2-2116 

1-227 

4-4052 

8    . 

0-4110 

0-5047 

2-2137 

1-228 

4-3859 

9    . 

0-4129 

0-5074 

2-2160 

1-229 

4-3668 

10    . 

0-4148 

0-5102 

2-2184 

1-230 

4-3478 

11    . 

0-4167 

0-5130 

2-2209 

1-231 

4-3289 

12    . 

0-4187 

0-5158 

2-2234 

1-232 

4-3103 

13    . 

0-4206 

0-5187 

2-2262 

1-233 

4-2918 

14    . 

0-4226 

0-5215 

2-2290 

1-231 

4-2734 

15    . 

0-4246 

0-5245 

2-2319 

1-235 

4-2553 

16    . 

0-4267 

0-5274 

2-2350 

1-236 

4-2372 

17    . 

0-4288 

0-5304 

2-2381 

1-237 

4-2194 

18    . 

0-4309 

0-5334 

2-2414' 

1-238  . 

4-2016 

19    . 

0-4330 

0-5365 

2-2448 

1-239 

4-1840 

20    . 

0-4351 

0-5396 

2-2483 

1-240 

4-1660 

21    . 

0-4373 

0-5427 

2-2519 

1-241 

4-1493 

22    . 

0-4395 

0-5458 

2-2557 

1-242 

4-1322 

23    . 

0-4417 

0-5490 

2-2595 

1-243 

4-1152 

24    . 

0-4439 

0-5523 

2-2636 

1-244 

4-0983 

25    . 

0-4462 

0-5555 

2-2677 

1-245 

4-0816 

26    . 

0-4485 

0-5589 

2-2719 

1-246 

4-0650 

27    . 

0-4508 

0-5622 

2-2763 

1-247 

4-0485 

28    . 

0-4532 

0-5636 

2-2808 

1-248 

4-0322 

29    . 

0-4556 

0-5690 

2-2854 

1-249 

4-0160 

30    . 

0-4580 

0-5725 

2-2902 

1-250 

4;0000 

AMYLO    PROCESS  155 

extract  the  alcohol  and  separate  it  from  the  water,  yeast,  and  other  solid  and  liquid  sub- 
stances. Before  the  distillation  apparatus  is  described,  certain  special  saccharification  and 
fermentation  processes,  which  have  been  recently  applied  practically,  will  be  considered. 

The  AMYLO  PROCESS  (Collette  or  Boidin  Process).  This  process  is  based  on  investi- 
gations of  Calmette,  Collette,  Boidin,  and  others,  who  found  that  certain  Mucors  (moulds, 
see  p.  133),  isolated  from  impure  Chinese  and  Japanese  ferments,  are  capable  of  performing 
the  functions  of  both  diastase  and  zymase,  that  is,  of  transforming  starch  into  alcohol  by 
way  of  maltose  and  dextrin.  Of  these  moulds,  Amylomyces  JRouxii,  discovered  by  Calmette 
in  1892,  and  the  Mucors  B  and  C  discovered  by  Collette,  Boidin,  and  Mousain,  are  of  most 
importance  industrially.1  Of  the  first  two,  the  forms  observed  under  the  microscope 
in  different  stages  of  development  are  shown  in  Fig.  127  (A,  B,  C,  D,  and  E). 

Collette  and  Boidin  patented  in  1897  (Eng.  Pat.  19,858)  a  process  for  the  industrial 
utilisation  of  Amylomyces  Rouxii  for  manufacturing  alcohol  directly  from  the  starch  of 

[i.  e.,  by  (q — 1)],  the  factor,  c,  for  the  difference  of  attenuation  is  obtained.     The  factor,  c,  is 

n 

used  for  the  analysis  of  liquids  for  which  the  value  of  p  is  unknown ;  also  ~  —  B'  (degree  of  real 

fermentation). 

The  following  illustrates  a  practical  calculation  :  the  original  saccharometric  degree  of  a 
wort  was  p  =  16-2,  that  after  fermentation  m  —  1,  and  that  after  boiling  n  =  3-9;  applying 
any  one  of  the  three  factors  (a,  b,  and  c)  given  in  the  appended  Table,  the  apparent  attenuation 
becomes  A  =  (p — m)  a  (where  p.  =  16-2,  a  =  0-4267)  =  6-4858  per  cent,  of  alcohol.  Calcu- 
lating according  to  the  real  attenuation,  A  =  (p — n)  b  (where  p  =  16-2,  n  —  3-9,  and  b  =  0-5274) 
=  6-4870  per  cent,  of  alcohol.  Lastly,  calculating  from  the  attenuation  difference,  D,  A  =  (n — m ) 
c  (where  c  =  2-2350)  =  6-4815  per  cent.  Hence  the  fermented  wash  consists  of  6-48  per  cent, 
of  alcohol,  3-9  per  cent,  of  unfermented  extract  (n),  and  89-62  per  cent,  of  water. 

B.  Wagner,  P.  Schultze,  and  J.  Rub  (1908)  suggest  the  Zeiss  immersion  refractometer  as  a 
means  of  determining  the  attenuation :  exact  results  are  obtained  rapidly  and  with  a  small 
quantity  of  liquid  (20  to  30  c.c. ).  A  little  of  the  wort  is  well  shaken  to  get  rid  of  carbon  dioxide, 
and  filtered  through  a  covered  filter,  5  c.c.  of  the  filtrate  being  used  to  determine  the  refracto- 
meter reading,  A,  at  a  temperature  of  17-5°;  a  further  20  c.c.  is  evaporated  to  one-half  the 
volume  in  a  porcelain  dish  to  expel  the  alcohol,  the  volume  being  then  made  up  exactly  to  20  c.c. 
with  water  and  the  refractometer  reading,  B,  taken.  To  the  difference,  A  —  B  —  G,  15  (the 
refractometer  reading  for  water)  is  added,  giving  E ;  the  corresponding  alcohol  degree  (by  volume), 
V,  is  then  found  in  the  following  Table,  and  may  be  subsequently  corrected  for  the  density  of 
the  wort : 

E:     16-2   17-5   18-8  20-1   21-4  22-8  24-2   25-6  27-1   28-6  30-1   31-7   33-3   34-9   36-4   38-0 
V:       1         2       3       4         5        6         7         8        9       10       11       12       13      14      15       16 

1  Among  the  Hyphomycetes  (moulds,  p.  133) — in  the  Mucor  and  Mucedince — Pasteur  found 
certain  varieties  (Mucor  racemosus)  capable  of  transforming  sugar  into  alcohol  and  carbon  dioxide 
when  they  live  immersed  in  the  liquid  out  of  contact  of  air  (like  the  yeasts);  in  presence  of  air, 
they  convert  the  sugar  directly  into  water  and  carbon  dioxide.  These  are  called  facultative 
anaerobic  organisms.  In  1887  Gayon  studied  other  varieties  which  behave  similarly  (Mucor 
alternans,  spinosus,  and  circinelloides),  and  Prinsen  Geerligs  investigated  Chlamydomucor  oryzce, 
which  is  used  in  Java  to  ferment  molasses.  In  1892  Calmette  imported  from  China,  studied, 
and  named  Amylomyces  Rouxii,  the  Mucor  isolated  from  the  rice-ferment  used  by  the  Chinese 
(which  is  more  active  than  the  Japanese  koji)  for  the  preparation  of  spirit;  later  he  found  this 
Mucor  in  rice-husks.  At  Tokyo  in  1894,  Takamine  studied,  and  applied  practically  to  the 
saccharification  of  rice,  Aspergillus  oryzce  (separated  from  Japanese  koji,  which  is  a  mixture  of 
yeasts  and  moulds  used  in  Japan  for  producing  alcoholic  fermentation),  but  it  did  not  meet  with 
success,  owing  to  its  action  being  too  energetic.  Boidin,  Collette,  and  Mousain  investigated 
Mucor  &,  which  is  another  Mucor  separated  from  Japanese  koji  and  is  different  from,  and  more 
important  industrially  than,  that  of  Takamine ;  Mucor  y,  which  was  separated  at  the  same  time 
from  Tonkin  rice,  is  of  still  greater  practical  value  than  Mucor  0. 

These  moulds  have  the  special  property  of  saccharifying  starch  and  of  fermenting  the  sugar 
thus  formed.  Their  saccharifying  and  fermentative  activity  is,  however,  influenced  by  the 
acids  that  they  produce.  Thus,  Amylomyces  Rouxii,  which  was  the  first  to  be  used  in  practice 
in  1898,  was  abandoned  later,  as  it  transforms  rather  too  much  sugar  into  carbon  dioxide  and 
water  and,  owing  to  the  production  of  1-45  grams  of  acid  per  litre  of  wort  (at  16°  Balling),  com- 
plete attenuation  is  obtained  only  in  very  dilute  worts  (7°  to  8°  Balling,  these  giving  4  to  4-5  per 
cent,  alcohol) ;  Mucor  &,  on  the  other  hand,  forms  only  0-75  gram  of  acid,  and  can  ferment  worts 
at  10°  to  17°  Balling  (which  give  8  to  9  per  cent,  of  alcohol)  without  oxidising  completely  more 
than  a  very  small  proportion  of  sugar. 

Calmette  studied  more  particularly  the  saccharifying  properties  of  Amylomyces  Rouxii,  but 
in  1897  Boidin  and  Rolants,  and  simultaneously  Sanguinetti  (Institut  Pasteur),  found  that  this 
mould  is  also  capable,  of  transforming  sugar  and  dextrin  into  alcohol ;  it  was  found  later  that 
Mucor  racemosus,  which  had  been  already  studied  by  Pasteur,  behaved  similarly.  In  1895 
Professor  Saito,  of  Tokyo,  isolated  Rhizopus  oligosporus,  which  acts  like  Amylomyces  Rouxii. 
Good  practical  results  are  obtained  also  with  pure  cultures  of  Mucor  Delemar. 


156 


ORGANIC    CHEMISTRY 


cereals,  etc.,  and  later  they  utilised  Mucor  ft.     At  the  present  time  this  process  is  employed 
on  an  enormous  scale  in  various  distilleries  in  France,  Belgium,  and  Italy  (at  Savona). 

As  it  is  necessary  to  work  with  perfectly  aseptic  worts,  the  starch-paste  prepared  in 
the  ordinary  way  with  the  Henze  apparatus  is  passed  into  closed  metal  cylinders  holding 
200  to  1000  hectolitres,  and  furnished  with  vertical  stirrers.  When  the  temperature  reaches 
65°,  1  per  cent,  of  malt  (on  the  amount  of  maize  used)  is  added  to  render  the  mass  rather 
more  liquid;  after  an  hour  the  mash  is  slightly  acidified  by  the  addition  of  0-1  gram  of 
sulphuric  acid  per  litre,  and  is  then  rendered  completely  sterile  by  passing  steam  in  at 
the  bottom  and  boiling  the  wort  until  the  steam  issues  freely  from  the  upper  aperture. 
The  apparatus  is  then  closed  hermetically,  a  vacuum  being  produced  by  the  condensation 


FIG.  127. 


A.  Colonies  of  Amylomyces  Rouxii  in  wort-gelatine.  B.  Mycelial  conidia  of  Amylomyces 
Rouxii  in  aerobic  cultures.  C.  Segmentation  into  gemmse  of  the  mycelium  of  Amylomyces 
in  anaerobic  culture.  D.  Hyphse  of  Mucor  ft  (1  :  100)  with  sporangia  in  aerobic  culture. 
E.  Mycelium  of  Mucor  $  with  spores  in  different  stages  of  development  in  anaerobic  culture  : 
1,  spores  just  separated;  2,  turgid  spores  ready  to  germinate;  3,  germinating  spores;  4, 
mycelium  (1  :600). 

of  the  steam.  The  vacuum  is  relieved  by  allowing  sterilised  air — filtered  through  cotton 
wool  (see  p.  150) — to  enter;  the  maintenance  of  a  slight  pressure  inside  the  vessel  prevents 
the  entry  of  germs.  By  stirring  the  starch  and  running  cold  water  down  the  outer  walls 
of  the  cylinder  1000  hectolitres  of  boiling  wort  may  be  cooled  in  five  hours  to  38° ;  this  is  the 
most  suitable  temperature  for  the  Mucor  fermentation,  but  a  great  part  of  the  sulphuric 
acid  added  must  first  be  neutralised.  A  vat  of  1000  hectolitres  capacity  contains 
150  to  200  quintals  (15  to  20  tons)  of  maize  and  six  times  as  much  water. 

The  Amylomyces  is  cultivated  in  the  laboratory  on  100  grams  of  rice  and  200  c.c.  of 
sterile  wort,  so  that  preferably  spores  are  developed.  Every  culture-flask  contains  a  total 
of  about  0-1  gram  of  spores,  and  this  quantity  is  sufficient  to  inoculate  1000  hectolitres 
of  wort.  The  Mucor  is  introduced,  under  aseptic  conditions,  into  the  vats  from  above 
and  the  stirrer  set  in  motion ;  a  little  air  is  introduced,  this  issuing  by  an  upper  tube  with 
a  hydraulic  seal.  In  the  course  of  twenty-four  hours  the  wort  is  attacked  by  an  abundant 
growth  of  the  Mucor.  The  mass  is  then  cooled  to  33°  and,  in  order  to  complete  the 


AMYLO    PROCESS 


157 


alcoholic  fermentation  more  rapidly,  a  small  quantity  of  ordinary  yeast  (500  c.c.  of  a 
wort  culture,  corresponding  with  3  to  4  grams  of  pressed  yeast)  is  added. 

After  three  to  four  days,  the  alcoholic  fermentation  is  complete  (the  carbon 
dioxide  passes  out  at  the  top  through  the  water-seal).  Fig.  128  shows  diagram- 
matically  a  plant  with  five  large  fermentation  vessels. 

The  advantages  of  the  Amylo  process  are:  (1)  a  considerable  saving  in 
malt,  only  about  1  per  cent,  being  used  instead  of  12  to  15  per  cent,  by  the 
old  process ;  further,  air-dried  malt  is  difficult  to  keep  in  hot  countries ;  (2)  the 
reduction  of  the  amount  of  yeast  required  to  a  minimum.  The  yield  of  alcohol 
is  also  sensibly  increased,  100  kilos  of  maize  containing  57  to  58  per  cent, 
of  starch  yielding  37'5  litres  of  alcohol,  i.  e.,  65  (often  66)  litres  of  pure  alcohol 
per  100  kilos  of  starch ;  the  old  method  of  working  gives  only  60  to  61  litres. 

The  increase  in  the  alcohol-yield  is  naturally  due  to  the  fermentation 
taking  place  in  a  wort  uncontaminated  with  extraneous  micro-organisms ;  on 


FIG.  128. 


rectification,  4  to  5  per  cent,  more  good  spirit  (bon  gout)  is  obtained  than  by 
the  old  process. 

Finally,  the  spent  wash  (residue  after  distillation)  filters  better,  since  it 
contains  less  dextrin  and  does  not  block  the  filter-presses.1 

1  In  a  German  distillery  the  Amylo  process  was  applied  in  1912  in  the  following  manner  : 
350  kilos  of  ground  maize  are  treated  for  an  hour  at  60°  with  1000  litres  of  water  containing  about 
3  litres  of  hydrochloric  acid  free  from  arsenic.  The  mass  is  then  steamed  for  forty-five  minutes 
at  4  atmos.  pressure  in  the  ordinary  Henze  type  vessel,  the  steam  issuing  from  the  air-cock. 
For  twenty  minutes  the  pressure  is  maintained  at  4-|  atmos.,  the  steam  being  then  discharged 
into  another  vessel  so  as  to  lower  the  pressure  to  2  atmos.,  at  which  it  is  kept  for  fifteen  minutes. 
Finally,  under  this  pressure  the  stirred  mass  is  forced  into  the  fermentation  vessel,  into  which 
also  two  similar  amounts  of  steamed  product  and  150  litres  of  boiling  wash-water  are  introduced. 
The  boiling  mass  is  kept  mixed  with  a  current  of  sterilised  air,  while  the  temperature  is  lowered 
to  40°  by  a  water-spray  applied  outside.  The  mass  is  then  seeded  with  a  pure  culture  of  Mucor 
Delemar,  which  multiplies  rapidly  at  35°  to  38°,  air  being  blown  through  for  twenty-four  hours. 
After  a  further  period  of  thirty -six  to  forty -two  hours  without  aeration  saccharification  is  com- 
plete, a  small  quantity  of  selected  alcoholic  ferment  being  then  added.  This  increases  rapidly 
in  twenty -four  hours  (with  aeration)  and  after  five  to  six  days  of  active  fermentation  (without 
aeration)  an  attenuation  of  0-5°  Balling  is  reached.  With  the  necessary  precautions  there  is 
no  danger  of  contamination,  and  the  residual  grains  form  an  excellent  cattle  food.  The  con- 
sumption of  coal  for  the  whole  process  is  900  kilos  per  1400  kilos  of  maize  treated,  and  the  jield 
is  as  much  as  37-7  litres  of  pure  alcohol  per  100  kilos  of  maize. 


158 


ORGANIC    CHEMISTRY 


DISTILLATION  OF  THE  FERMENTED  LIQUID.  As  has  already  been  stated, 
the  fermentation  is  rendered  the  more  complete  by  using  worts  which  are  not  too  con- 
centrated and  yield  9  to  10  per  cent,  of  ethyl  alcohol.  These  fermented  liquids  contain  also 
small  quantities  of  various  other  substances,  such  as  aldehydes,  organic  acids  (acetic, 
propionic,  butyric,  lactic,  succinic,  etc.),  certain  higher  alcohols  (amyl,  propyl,  butyl, 
glycerol),  etc.,  besides  the  solid  residues  of  cereals  and  yeast  and  small  amounts  of 
unfermented  dextrin  and  starch. 

It  was  formerly  not  easy  to  separate  the  ethyl  alcohol  from  these  products,  in  spite 
of  the  great  differences  in  boiling-point  in  some  cases  (amyl  alcohol,  132° ;  ethyl  alcohol, 
78-4°),  and,  as  already  explained  on  p.  130,  this  separation  cannot  be  effected  with  the 
most  exact  fractional  distillation,  so  that  recourse  must  be  had  to  rectification  (see  p.  3).1 
Every  distillation  apparatus  is  now  composed  of  four  parts :  (1)  the  boiler  in  which 
the  alcoholic  liquid  is  heated;  (2)  the  rectifier;  (3)  the  dephlegmator ;  and  (4)  the  con- 
denser. The  liquid  collecting  in  the  dephlegmator  returns  to  the  column  (hotter),  where 
alcohol  vapours  are  formed  richer  than  those  from  which  it  was  formed  in  the  first  distil- 
lation; so  that  the  alcohol  vapours  of  the  dephlegmator,  uniting  with  the  other  vapours 
before  the  condenser  is  reached,  contribute  to  form  a  more  con- 
centrated alcohol. 

Apparatus  with  continuously  working  columns  and  with  recovery 
of  the  heat  were  studied  and  applied  by  Coffey  (Eng.  Pat.  5974), 
but  more  thoroughly  in  1867  by  Savalle. 

The  action  of  a  rectifying  column  may  be  understood  from  Fig. 
129,  showing  part  of  the  column,  which  is  divided  into  a  number  of 
chambers  communicating  by  means  of  tubes  and  placed  above  the 
boiler.  The  mixture  of  alcohol  and  water  vapours  from  the  boiling 
fermented  wash  below  -ascends  the  column  from  chamber  to 
chamber  through  the  central  tubes,  which  are  covered  with  caps 
dipping  below  the  surface  of  the  liquid  in  the  chambers ;  by  this 
arrangement  the  mixed  vapours  are  obliged  to  pass  through  the 
hot,  condensed  liquid,  which  slowly  descends  the  column  through 
the  drop-tubes,  when  it  reaches  a  certain  level  in  each  chamber. 
The  vapours  give  up  to  the  liquid  mainly  water- vapour,  and  the 
liquid  gives  up  to  the  vapours  preferably  the  alcohol  it  contains,  so 
that  the  alcohol- vapour  reaches  the  top  of  the  column  mixed  with 
only  a  little  water- vapour  and  passes  to  the  condenser,  whilst  water 
almost  free  from  alcohol  flows  downwards,  forming  vinasse  or  spent 
wash. 

With  this  column,  8  to  10  metres  high  and  containing  20  to  25 

plates  or  chambers,  one  distillation  and  partial  rectification  yield  directly  a  crude  50  to 
65  per  cent,  alcohol,  and  when  this  is  subjected  to  a  second  similar  distillation  and 
rectification  a  concentration  of  90  per  cent,  or  even  96  per  cent,  is  attained;  each 
apparatus  gives  a  high  output.  This  is  the  procedure  often  adopted  in  France. 

Taller  columns  (14  to  18  metres)  are,  however,  used,  especially  in  Germany,  and  these 
with  efficient  dephlegmators  give  90  per  cent,  or  even  96  per  cent,  alcohol  in  one  continuous, 
although  slower,  operation.  The  cylindrical  columns  are  advantageously  replaced  by 

1  The  first  forms  of  distillation  apparatus  were  used  in  the  times  of  the  ancient  Arabs,  and 
were  termed  alembics.  The  alchemists  made  improvements  in  the  shape,  especially  of  the  part 
used  for  condensing.  Simple  distillation  apparatus,  like  that  used  for  obtaining  distilled  water 
(Vol.  1.,  p.  253)  yield  a  highly  aqueous  spirit,  termed  phlegm.  Argand,  and  later  Adam  (about 
1800),  utilised  the  heat  of  the  aqueous  alcoholic  vapours  distilling  over  to  heat  the  liquid  to  be 
distilled.  Solimani  and  Berard  (1805)  improved  the  apparatus  so  as  to  allow  a  distillate  moder- 
ately rich  in  alcohol  to  be  obtained  in  a  single  operation.  Before  the  condenser  was  placed  a 
vessel  called  a  dephlegmator,  which  condensed  part  of  the  water- vapour  and  part  of  the  alcohol 
(phlegm),  more  concentrated  alcohol  vapours  passing  to  the  condenser.  The  first  really  rational 
and  complete  apparatus  for  the  fractional  distillation  of  alcohol  was  constructed  by  Cellier- 
Blumenthal  (1815),  who  used  dephlegmators  and  the  first  rudimentary  rectifiers,  but  as  early 
as  1813  A.  Baglioni  had  placed  semi-rectifying  dephlegmators  directly  above  the  boiler. 

The  first  column  rectifying  dephlegmator  was  devised  by  Derosne  and  Gail  in  1817,  and  shortly 
afterwards  widespread  use  was  made  of  the  very  convenient  Pistorius  apparatus,  with  its  flat, 
lenticular  dephlegmators,  which  allows  of  60  to  75  per  cent,  alcohol  being  obtained  directly 
and  is  still  used  in  some  of  the  smaller  distilleries. 


FIG.  129. 


DISTILLATION  159 

square  ones,  which  are  less  easily  stopped  up  and  more  easily  cleaned  and  repaired;  in 
place  of  the  costly  copper  columns,  cheaper  cast-iron  ones  are  now  largely  used.  A  square 
plate  of  such  a  Savalle  column  is  shown  diagrammatically  in  Fig.  130,  the  apertures  and 
tubes  being  sufficiently  wide  to  avoid  obstructions  when  dense  fermented  worts,  rich  in 
solid  matters,  are  distilled.  The  heating  of  the  column  and  of  the  liquid  is  no  longer 
effected  by  direct  steam,  as  this  causes  useless  dilution ;  indirect  steam  is  employed  with 
a  tubular  heater,  to  be  described  later.  In  order  to  obtain  regularity  of  working  and 
constancy  in  the  alcoholic  strength  an  automatic  steam  regulator  is  used  (see  below), 
and  the  supply  of  fermented  wash  to  the  apparatus  is  so  controlled  that  the  yield  and 
strength  of  the  alcohol  remain  uniform.  The  heat  of  condensation  of  the  alcohol  vapours 
is  recovered  to  heat  the  wash,  and  the  latter,  before  being  introduced  into  the  top  of  the 
column,  is  passed  through  tubular  heaters  so  as  to  utilise  also  the  heat  of  the  spent  wash 
before  this  is  discarded. 

Fig.  131  shows  the  whole  of  a  Savalle  continuous  distilling  apparatus.  The  wash  to 
be  distilled  passes  from  large  constant-level  tanks,  situate  on  the  upper  floors,  through 
the  tube  m,  furnished  with  a  regulating  cock,  2,  into  the  bottom  of  the  heater,  C,  from 
which  it  issues  at  the  top,  after  serving  to  condense  the  alcohol  vapours  coming  from  the 
column  by  the  tube  k ;  these  vapours,  however,  first  yield  a  little  condensed  spirit  in  B, 
this  being  carried  to  the  column  by  the  tube  r.  The  heated  wash  passes  along  the  pipe  q 
to  the  top  of  the  column  and  slowly  descends,  meeting  meanwhile  the  ascending  vapour 
current,  to  which  it  gradually  gives  up  its  alcohol,  as  stated  above  (see  Fig.  129).  The 
alcohol  condensed  in  the  wash-heater  is  cooled  in  the  condenser,  D,  below,  through  which 
cold  water  circulates.  If  the  wash  is  heated  in  the  wash- heater  sufficiently  to  form  vapour, 
this  passes  into  the  small  dephlegmator,  H, 
whence  the  condensed  alcohol  and  water  are 
led  by  the  tube  S  r  to  the  column,  whilst  the 
alcohol  vapour  which  is  not  condensed  pro- 
ceeds through  t  to  the  condenser  along  with 
the  other  alcohol.  When  all  the  plates  of 
the  column  are  covered  with  wash,  steam  is  FIG.  130. 

passed  in  from  below  by  heating  the  exhausted 

vinasse  by  pipes  from  the  heater,  0,  in  which  superheated  steam  from  suitable  boilers 
circulates;  this  steam  is  regulated  by  the  tap  j,  which  in  its  turn  is  controlled  by  the 
automatic  regulator  F.  When  the  distilled  alcohol  issues  from  the  test-glass,  E,  the  access 
of  wash  through  2  is  regulated  so  that  the  alcoholic  strength  remains  constant.  In  the 
column  the  wash  traverses  a  path  more  than  125  metres  in  length,  the  total  absorptive 
surface  being  more  than  200  sq.  metres,  so  that  every  litre  of  wash,  before  exhaustion, 
meets  a  surface  of  vapour  200  metres  long.  In  this  way  30,000  kilos  or  more  of  wash 
may  be  distilled  per  day  without  interruption  of  the  working  for  months. 

Fig.  132  shows  Savalle's  tubular  heater  more  in  detail.  Steam  under  pressure  from 
ordinary  boilers  traverses  the  regulator,  E,  and  passes  through  the  tube  i  to  a  large  metallic 
cylinder,  G,  which  contains  a  series  of  vertical  tubes  connecting  the  upper  chamber,  G', 
with  the  lower  one,  G";  the  latter  is  filled  with  almost  exhausted  vinasse  supplied  from 
the  lower  part  of  the  Savalle  column  by  the  pipe  x.  The  spent  wash,  which  is  already 
very  hot,  is  thus  easily  brought  into  a  condition  of  vigorous  ebullition  and  loses  the  last 
traces  of  alcohol,  which  rise  with  a  large  quantity  of  steam  through  the  pipe  y  into  the 
Savalle  column.  The  exhausted  spent  wash  is  discharged  continuously  from  the  tube  7, 
whilst  the  condensed  steam  issues  from  the  tap  8. 

Fig.  133  shows  the  automatic  regulator  of  the  pressure  and  steam  in  the  distilling  and 
rectifying  column.  In  order  that  it  may  pass  through  all  the  layers  of  liquid  on  the  plates 
of  the  column,  the  steam  must  be  at  a  certain  pressure  in  the  column  itself ;  this  pressure 
increases  or  diminishes  according  as  the  quantity  and  temperature  of  the  steam  rise  or 
fall,  and  the  greater  the  supply  of  steam  the  more  dilute  will  be  the  alcohol.  If  the  column 
is  connected  with  the  pressure  regulator  by  means  of  the  tube  F  (/in  Fig.  131),  then, 
when  the  pressure  increases,  the  water  in  the  lower  chamber,  A,  of  the  regulator  is  forced 
along  the  tube  B  to  the  upper  chamber  and  raises  a  float,  C,  which  operates  the  lever  D, 
and  so  partially  closes  the  tap  (or  valve)  E  controlling  the  supply  of  steam  to  the  heater,  G; 
owing  to  the  diminished  supply  of  steam  the  pressure  falls.  In  the  opposite  case,  when 
the  pressure  in  the  column  is  smaller  than  that  necessary  for  regular  distillation,  so  that 


160 


ORGANIC    CHEMISTRY 


the  concentration  of  the  alcohol  (measured  in  E,  Figs.  131  and  134)  becomes  too  high  and 
the  yield  too  small,  the  water  of  the  upper  chamber  of  the  regulator  descends  to  the  lower 
one,  the  float,  C,  hence  falling  and  the  steam-cock,  E,  opening  a  little.  With  these  regu- 


lators,  which  are  sensitive  to  variations  of  one-thousandth  part  of  an  atmosphere,  the 
distillation  is  automatically  regulated  and  requires  very  little  personal  control. 

The  constancy  of  the  strength  of  the  alcoholic  distillate  is  controlled  by  the  test-glass,  E 
(see  Fig.  134),  which  is  situated  in  the  alcohol  discharge  tube  and  contains  an  alcohol- 
meter  fitted  with  a  thermometer,  so  that  the  concentration  and  temperature  are  indicated 
continuously. 


CONTINUOUS    DISTILLATION 


161 


Of  the  variously  highly  perfected  forms  of  apparatus  (Ilges,  Coffey,  Pampe,  the  last  of 
which  gives  very  pure  spirit  by  distillation  under  reduced  pressure)  used  in  Britain, 
Germany,  Russia,  etc.,  which  allow  of  the  continuous  and  direct  production  of  90  to  96  per 
cent,  alcohol  without  special  rectification  and  refining  (when  the  first  and  last  products 

of  distillation— -foreshots  and  tailings— are  kept  separate ; 
see  later),  we  shall  refer  only  to  the  apparatus  of 
Siemens  Brothers,  which  is  largely  used  in  Germany 

Hlffll  ^lL,1  •       (Fig.  135);  the  new  Kubierschky  column  is  described 

later  (see  chapter  on  Tar  Oils   and   Benzene).     The 


FIG.  132. 


FIG.  133. 


Siemens  column  is  composed  of  three  principal  parts  :  the  heater  (or  pre-heater),  A,  the 
distillation  column,  B,  and  the  rectifier,  C;  the  whole  is  formed  of  superposed  cast-iron 
discs  or  rings  fitted  with  pasteboard  packing  and  held  tightly  together  by  bolts  extending 
from  the  top  to  the  bottom.  Inside  are  plates  arranged  spirally  round  a  central  tube,  D, 
which  passes  about  half-way  up  the  column  to  /;  the  liquids  thus  traverse  a  long  path, 
so  that  a  large  production  is  possible  with  a 
relatively  small  tower-space.  The  apparatus  is 
also  economical,  since  it  is  not  necessary  to  con- 
struct it  of  copper.  The  heater,  A  (see  also  Fig.  136, 
A),  contains,  in  the  chambers  a  and  o,  hot  spent 
wash  which  comes  from  the  top  of  the  column. 
Between  these  hot  chambers  are  arranged  altern- 
ately others  in  which  circulates  the  cold  wash  or 
wine  to  be  distilled;  this  is  supplied  through  the 
pipe  d  by  means  of  high-pressure  pumps,  and 
begins  to  be  heated  as  it  descends  the  spiral 
chambers  between  the  hot  ones  containing  the 
spent  wash.  When  it  reaches  the  bottom  the  hot 
wash  passes  into  the  central  pipe  D,  and  rises  to 
the  higher  level,  /,  in  the  distillation  column,  B 
(which  embraces  the  space  between  d  and  E). 
The  pipe  D  empties  on  to  the  perforated  spiral 

plates  (see  Fig.  136,  B)  and,  as  it  descends,  the  wash  meets  a  current  of  steam  rising 
from  the  tube  o  through  B.  In  this  way  the  alcohol  liberated  from  the  wash  rises  with 
the  steam  through  the  perforations  of  the  spiral  plates  and  thus  continually  meets  fresh 
quantities  of  wash  and  becomes  continually  richer  in  alcohol,  as  is  shown  in  Fig.  136,  B. 
The  wash,  thus  deprived  of  alcohol,  reaches  the  bottom  as  very  hot  spent  wash,  which, 
VOL.  II.  1 1 


FIG.  134. 


162 


ORGANIC    CHEMISTRY 


before  leaving  the  column,  traverses  the  chambers  of  the  heater  (shown  in  Fig.  136,  .4), 
and  is  then  discharged  continuously  from  the  pipe  J  K,  at  a  lower  level  than  /.  The 
mixed  alcohol  and  water  vapours  enter  the  rectifying  compartment,  E,1  which  is  formed 
of  plain  discs  and  is  filled  with  wash,  the  level  of  which  may  be  seen  through  suitable  glass 
windows.  The  alcohol  vapours  rise  into  the  rectifier,  C  (more  properly  termed  a  frac- 
tionalor  or  dephlegmator,  see  p.  158),  formed  of 
non- perforated  and  hence  non-communicating  spiral 
chambers  (Fig.  136,  C),  in  some  of  which  circulate 
the  ascending  vaporous  mixture,  whilst  the  alternate 
ones  are  traversed  by  a  descending  current  of 
water ;  the  latter  is  not  very  cold,  as  it  comes  from 


FIG.  136. 

the  top  of  the  condenser,  S  (by  means  of  the  pipe  t),  so  that  it  condenses  mainly  steam 
and  only  a  little  alcohol  vapour,  which  falls  into  the  distilling  column  again.  The 
alcohol  vapours  gradually  become  more  and  more  highly  concentrated  and  pass  through 
the  tube  F  to  the  refrigerator,  S,  where  they  condense  and  are  cooled  by  water  flowing 
in  at  s  and  out  at  t.  By  means  of  a  sample  taken  from  the  column  B  by  the  tube  p  and 

1  Pampe  (Ger.  Pat.  199,142,  1908)  suggests  placing,  before  the  rectifying  compartment,  a 
steam-turbine  with  rapidly  rotating  vanes,  which  separate  all  the  suspended  drops  or  impurities 
from  the  vapours. 


HORIZONTAL    COLUMNS 


163 


examined  in  the  tester,  T,  it  can  be  ascertained  if  the  spent  wash  is  completely  free 
from  alcohol. 

In  some  cases  it  is  observed  that  the  spirit  from  such  a  cast-iron  apparatus  absorbs 
traces  of  hydrocarbons  and  of  hydrogen  sulphide  which  are  formed  from  the  iron  and 
give  an  unpleasant  taste  and  smell  to  the  alcohol ;  this  may,  perhaps,  depend  on  the  quality 
of  the  metal  and  on  the  newness  of  the  apparatus. 

We  shall  mention  finally  the  attempts  which  have  been  made,  first  by  Perrier  in  1875, 
to  transform  the  vertical  column  into  a  horizontal  distilling  and  rectifying  column  with 
a  central  rotating  axis  carrying  helically  arranged  blades,  which  transport  even  a  very 
dense  wash  from  one  end  to  the  other,  whilst  the  opposing  current  of  steam  removes  the 
whole  of  the  alcohol.  The  process  was  perfected  by  Sorel  and  Savalle  (1891 ),  who  arranged 
the  numerous  vertical  chambers  of  the  horizontal  column  in  a  more  rational  manner. 


FIG.  137. 

A,  distilling  column;  a,  entrance  of  the  wash  into  the  heater  or  refrigerator;  B,  con- 
denser and  heater;  b,  hot  wash  pipe ;  C,  adjustable  steam  regulator;  c,  exit  for  spent  wash ; 
D,  hot  wash  extractor  used  as  heater;  d,  steam -cock;  E,  test-glass  giving  the  strength  of 
the  alcohol;  e,  valve  regulating  flow  and  hence  strength  of  the  alcohol;  h,  entrance  of 
water  into  refrigerators  in  case  of  need. 

These  forms  are  not  yet  free  from  disadvantages,  but  they  have  the  advantage  of  being 
considerably  more  economical  to  construct  and  of  bringing  all  the  taps  conveniently  to 
hand  on  the  same  level. 

Lastly,  Guillaume  eliminated  various  defects  of  these  columns  and  at  the  same  time 
retained  all  their  advantages  by  employing  very  simple  and  convenient  inclined  columns 
(made  by  Egrot,  of  Paris),  which  allow  of  very  dense  washes  being  employed  without 
danger  of  obstruction.  Fig.  137  shows  the  complete  Guillaume-Egrot  apparatus,  and 
the  description  of  the  various  parts  given  underneath  will  indicate  the  way  in  which  it 
works.  The  cross-section  shown  in  Fig.  138  gives  an  idea  of  the  internal  arrangement  of 
the  inclined  column,  and  Fig.  139  represents  the  ground  plan  of  the  column,  the  arrows 
indicating  the  horizontal,  zigzag  course  followed  by  the  liquid  from  the  highest  part  of 
the  column,  whilst  the  vapours  ascend  the  column  in  a  zigzag  vertical  path  and  bubble 
through  the  liquid  in  all  the  chambers  formed  by  the  numerous  vertical  partitions.  With 
relatively  small  plant,  which  may  be  mounted  on  portable  cars  (see  later),  30,000  litres  or 


164 


ORGANIC    CHEMISTRY 


more  of  wash,  containing  10  per  cent,  of  alcohol,  may  be  distilled  per  twenty-four  hours, 

90  per  cent,  alcohol  being  produced. 

In  the  modern  distillery  the  consumption  of  steam  should  not  exceed  25  kilos  (about' 

3  kilos  of  coal)  per  100  kilos  of  wash,  and  the  consumption  of  water  in  the  condenser  should 

not  exceed  80  litres. 

RECTIFICATION  OF  ALCOHOL.     The  alcohol  obtained  with  the  ordinary  Savalle 

apparatus  is  not  sufficiently  concentrated  or  pure  to  be  placed  on  the  market,  and  even 

that  obtained  with  other 
forms  from  washes  which 
have  not  been  fermented 
with  selected  yeasts  should 
be  freed  by  rectification  and 
refining  (see  later)  from  vari- 
ous impurities  which  impair 
the  colour,  smell,  and  taste. 
These  impurities  may  be  more 
volatile  than  alcohol  (such 
as  aldehydes  and  certain 
esters)  or  less  volatile  (as 
acetic  and  butyric  acids; 
propyl,  isopropyl,  and  amyl 
alcohols ;  various  esters,  etc. ), 
and  they  are  separated  from, 
the  true,  alcohol  if,  in  the 
redistillation  and  rectifica- 
tion, the  portions  which  distil 
most  readily  (foreshots)  and 
FIG.  138.  also  the  least  volatile  por- 

tions   (tailings  or  fusel    oil, 

which  has  a  very  disagreeable  odour  if  obtained  from  potatoes,  molasses,  or  maize,  but  a 

pleasing  odour  if  derived  from  grapes,  fruit,  etc.)  are  kept  apart. 

Rectification  apparatus  usually  consists  of  a  large  copper  or  iron  boiler,  A  (Fig.  140), 

which  is  heated  with  an  indirect  steam-coil  and  on  which  is  mounted  the  copper  rectifying 

column,  B.     Above  this  and  to  one  side  is  a  large  dephlegmator,  C,  which  serves  as  a  heater, 

and  is  of  importance  not  so 

much  for  condensing  the  less 

volatile     products      (water, 

amyl   alcohol,  etc.)    as   for 

furnishing  a  continuous  and 

abundant  supply  of  a  suit- 
able alcoholic  liquid  to  wash 

the  vapours  arriving  at  the 

top  of   the   column;    it  is, 

however,    quite    useless    to 

employ     several      dephleg- 

mators,  as  was  erroneously 

done  in  the  past.  The  fore- 
shots,  which  have  a  con- 
centration up  to  94  per  cent. 

and  boil  at  85°,  are  collected 

separately.    Then  from  85°  FIG.  139. 

to  102°  alcohol  passes  over. 

The  tailings,  boiling  above  102°,  are  collected  in  the  bottom  of  the  column  by  shutting 

off  the  steam  and  thus  emptying  the  plates.     The  quantities  of  these  products  vary 

according  to  the  quality  of  the  alcohol  required ;  thus  20  per  cent,  of  foreshots  and  tailings 

may  be  obtained  and  80  per  cent,  of  alcohol  (bon  gout  extra),  or  5  per  cent,  of  foreshots 

and  tailings  and  95  per  cent,  of  alcohol  (bon  gout). 

This  apparatus  does  not  work  continuously,  the   boiler  requiring  to   be   discharged 

and  recharged.     Attempts  to  render  the  process  continuous  were  met  with  success  in  1881 


FUSEL    OIL 


165 


(E.  Bar  bet),  in  spite  of  the  difficulty  of  separating  the  pure  alcohol  from  an  impure  product 
that  boils  below  it  and  another  that  boils  above  it.  This  is  effected  by  carrying  out  the 
operation  in  two  phases,  which  are,  however,  continuous ;  in  the  first  phase  the  f oreshots 
are  driven  off  and  the  alcohol  distilled  from  the  remaining  liquid,  the  tailings  being  left 
behind.  The  boiler  is  then  replaced  by  a  rectifying  column,  which  receives  the  impure 
product  and  distils  the  foreshots,  passing  the  residue  continuously  at  a  certain  height  to 
a  second  lower  column  at  the  side;  this  distils  and  rectifies  the  pure  alcohol  and  retains 
in  the  lowest  chamber  of  the 
column  the  tailings,  which  are 
continuously  discharged.1 

1  The  tailings  vary  somewhat  in 
percentage  composition  :  water,  14 
to  24 ;  ethyl  alcohol,  15  to  45 ;  normal 
propyl  alcohol,  6  to  14;  isobutyl 
alcohol,  10  to  25;  amyl  alcohol  of 
fermentation,  10  to  40. 

The  fusel  oil  is  separated  from 
the  tailings  by  addition  of  a  saturated 
salt  solution  and  then  forms  a  more 
or  less  yellow  oil,  which  has  the 
unpleasant  odour  of  amyl  alcohol 
and  excites  coughing;  its  specific 
gravity  is  about  0-83  and  it  boils 
between  80°  and  134°,  mainly  at 
130°.  It  varies  in  composition  and 
contains  principally  amyl  alcohol 
(especially  that  obtained  from  mo- 
lasses), together  with  different  pro- 
portions of  normal  propyl  and 
isobutyl  alcohols,  caproic,  caprylic, 
capric,  acetic,  and  butyric  acids, 
esters,  furfural,  and  certain  bases, 
besides  8  to  10  per  cent,  of  ethyl 
alcohol. 

The  percentage  compositions  of 
two  samples  of  fusel  oil  obtained 
(a)  from  potatoes  and  (6)  from  grain, 
are  as  follows  :  normal  propyl  alcohol, 
6-854  (a),  3-69  (&);  isobutyl  alcohol, 
24-35  (a),  15-76  (6);  amyl  alcohol, 
68-76  (a),  75-89  (&);  fatty  acids, 
0-011  (a),  0-16  (6);  esters  of  fatty 
acids,  0-02  (a),  0-305  (&);  furfural, 
bases,  etc.,  0-005  (a),  0-021  (b)  (G. 
Boobey,  1913). 

Owing  to  its  poisonous  properties, 
fusel  oil  must  be  denatured  before 
being  sold  in  Italy,  so  that  it  cannot 
be  added  to  alcoholic  beverages. 

Fusel  oil  is  now  largely  used  for 
the  preparation  of  amyl  alcohol, 
which  is  used  in  the  manufacture 
of  fruit  essences  (see  later :  Amyl 
acetate),  for  obtaining  nitrous  and 
other  ethers,  and  for  gelatinising 
explosives  (nitrocellulose ) ;  during 
the  last  five  years  the  price  of  fusel 
oil  has  risen  from  65  to  170,  and 
even  195  lire  per  quintal.  Pasteur 
thought  that  the  amyl  alcohol  (iso- 

and  d-amyl)  arose  from  the  action  of  specific  bacteria  on  the  sugar,  but  in  recent  years  F. 
Ehrlich  has  thrown  doubt  on  the  formation  of  an  alcohol  with  a  branched  chain  from  a  sugar 
with  a  direct  chain,  and  has  now  shown  that  it  is  the  proteins  of  the  malt  and  their  decomposi- 
tion products  which  furnish  nitrogen  to  the  yeast  for  the  synthesis  of  its  protein  constituents 
and  at  the  same  time  form  amyl  alcohol.  In  fact,  in  the  fermentation  of  a  pure  sugar,  Ehrlich 
obtained  a  quantity  of  fusel  oil  proportional  to  the  quantity  of  leucine  added  ;  he  was  also  able  to 
obtain  an  amount  of  fusel  oil  equal  to  7  per  cent,  of  the  alcohol  formed  (the  usual  amount  being 
0-4  to  0-6  per  cent.)  and,  further,  he  succeeded  in  reducing  the  formation  of  fusel  oil  considerably 
by  the  addition  of  ammonium  salts.  The  United  States  imported  2100  tons  of  fusel  oil  in  1910 
and  2740  tons  (£236,000)  in  1911. 


FIG.  140. 


166 


ORGANIC    CHEMISTRY 


In  the  Savalle  rectifiers  45  kilos  of  coal  are  consumed  per  hectolitre  of  pure  rectified 
alcohol.  Continuous  rectification  results  in  a  saving  of  almost  50  per  cent,  of  fuel  compared 
with  the  discontinuous  process.  During  rectification  the  loss  of  alcohol  is  1  to  2  per  cent., 
and  the  cost  of  rectification  varies  from  3  to  3-5  lire  (2s.  6d.  to  3s. )  per  hectolitre.  The  firm 
of  Savalle  holds  that  it  is  more  economical  to  use  cold  air  than  water  in  the  refrigerators  of 
the  condensers. 

Attention  may  lastly  be  drawn  to  the  ingenious  although  complicated  Perrier  distilling 
and  rectifying  apparatus,  in  which  the  vapours  of  alcohol,  water,  higher  alcohols,  and 
aldehydes  are  passed  successively  into  columns  filled  with  glass  beads  and  surrounded  by 
a  jacket  containing  a  liquid  boiling  at  a  constant  temperature,  the  latter  being  hence 
assumed  by  the  whole  of  the  tower.  In  one  of  these,  having  a  temperature  of  85°  to  90°, 
only  water  and  the  tailings  are  condensed ;  the  vapours  then  pass  into  a  second  tower, 
kept  at  75°,  where  all  the  ethyl  alcohol  (which  may  be  rectified  in  another  tower)  separates ; 
the  vapours  from  this  form  the  foreshots  and  are  condensed  in  a  succeeding  tower. 

OTHER  PRIME  MATERIALS  FOR  THE  MANUFACTURE  OF  ALCOHOL. 
(I )  Beetroot  and  Molasses.  It  is  especially  in  France  that  considerable  quantities  of  beet 

are  used  for  the  manufacture  of  alcohol  instead 
of  sugar;  this  is  never  done  in  Germany  or 
Italy.  The  beets  are  washed  and  minced,  and 
the  pulp  exhausted  by  pressure,  maceration,  or 
diffusion  with  water.  This  treatment  is  described 
in  the  section  on  sugar. 

The  spirit  obtained  from  the  beet  is  less 
pure  than  that  from  potatoes,  containing  more 
propyl  and  butyl  alcohols  but  less  amyl  alcohol. 
Of  more  importance  in  Italy  and  various 
other  countries  is  the  utilisation  of  beet-molasses.1 
The  complete  fermentation  of  molasses  has 
presented  many  difficulties,  which  have  now 
been  overcome.  Formerly,  after  the  molasses 
was  diluted  to  8°  to  10°  Be.  (this  was  carried  out 
in  vats  provided  with  stirrers,  see  Fig.  141),  it 
was  slightly  acidified  with  sulphuric  acid  [2-5 
grams  of  free  H2S04  per  litre.  E.  Legier  (1913) 

replaced  the  sulphuric  acid  advantageously  by  a  smaller  amount  of  hydrochloric  acid, 
pure  yeasts  acclimatised  to  worts  containing  traces  of  formaldehyde  being  used],  as  the 
reaction  is  usually  alkaline.  The  liquid  was  then  boiled  for  some  hours  in  a  current  of 
air  in  .order  to  eliminate  the  volatile  acids  (nitric,  etc.)  liberated,  and,  after  cooling  it 
to  15°,  alcoholic  fermentation  was  initiated  by  the  addition  of  vigorously  fermenting 

The  annual  output  in  Germany  is  estimated  at  about  1000  tons,  and  in  1912  Germany 
imported  124  tons  and  exported  197  tons.  The  price  at  one  time  was  very  low  :  in  1911  less 
than  £28  per  ton,  in  1905  £70,  in  1910  £100,  and  in  1913  £144. 

1  This  is  the  dense,  viscous,  and  blackish  mother-liquor  which  remains  from  the  final  crystal- 
lisation of  the  sugar  (which  see)  and  from  which  no  further  sugar  will  crystallise,  although  45  to 
50  per  cent,  is  present  (see  explanation  in  the  section  on  Sugar) ;  it  has  a  density  of  40°  to  45°  Be. 
(74°  to  84°  Balling).  The  composition  of  beet-molasses  is  as  follows  :  water,  16  to  20  per  cent. ; 
sugar,  44  to  52  per  cent. ;  non -nitrogenous  extractive  matters,  10  to  15  per  cent,  (largely  pentoses ) ; 
nitrogenous  compounds,  6-5  to  9-5  per  cent,  (of  which  only  one-third  consists  of  proteins,  the 
rest  being  amino-acids);  ash  (deducting  C02),  8-5  to  11  percent.  In  Italy  the  working -up  of 
molasses  has  assumed  considerable  importance  during  the  last  few  years,  owing  to  a  change  in 
the  method  of  taxing  sugar;  previous  to  1903,  sugar  recovered  from  molasses  by  somewhat 
expensive  processes  (see  Sugar)  was  exempt  from  taxation,  whilst  nowadays  all  sugar  produced 
is  taxed  uniformly,  so  that  the  manufacturers  find  it  advantageous  to  sell  the  molasses  to  the 
distillery  at  £2  8s.  to  £3  4s.  per  ton  (pre-war  price).  In  1907  the  Italian  distilleries  used  38,000 
tons  of  molasses,  obtaining  97,330  hectolitres  of  alcohol,  while  in  1912  125,000  hectolitres  were 
obtained  from  56,000  tons. 

In  Germany,  Belgium,  and  part  of  France,  it  is  found  to  be  more  convenient  and  rational 
to  utilise  a  large  proportion  of  the  molasses  as  cattle-food  after  absorbing  it  by  highly  porous 
vegetable  substances.  In  Italy,  tumelina,  patented  by  E.  Molinari,  and  sanguemelassa  (blood- 
molasses),  patented  by  L.  Fino,  are  manufactured;  the  residues  of  dried  tomatoes  (Squassi, 
Bono)  and  various  other  dried  industrial  products  are  now  used  as  absorbents.  In  Germany 
more  than  150,000  tons  of  molassic  fodder  are  consumed;  Italy  produced  40,000  tons  in  1908 
and  more  than  48,000  in  1909. 


FIG.  141. 


ALCOHOL    FROM    MOLASSES  167 

liquid  and  the  excess  of  acid  which  forms  gradually  neutralised  with  chalk.  The  spirit 
thus  obtained  is  difficult  to  purify,  as  it  contains  an  aldehyde  and  various  acids  which 
boil  at  very  low  temperatures. 

To-day,  however,  the  process  is  much  more  simple,  as  Jacquemin  and  Effront  have 
devised  various  methods  of  preparing  races  of  yeast  capable  of  living  actively  in  worts 
rich  in  salts  (nitrates,  carbonates,  etc.),  such  as  those  prepared  from  beet-molasses.  In 
the  past  the  difficulty  of  fermentation  was  attributed  to  the  presence  of  nitrates,  but  it 
appears  from  Fernbach  and  Langenberg's  experiments  (1910)  that  nitrates,  even  in 
proportions  as  great  as  0-3  per  cent.,  facilitate  fermentation. 

(a)  In  the  Jacquemin  process  the  fermentation  is  initiated  in  small  quantities  of  wort 
in  suitable  vessels  (see  Fig.  125,  p.  150),  and  the  wort  of  the  last  rather  larger  vessel  (into 
which  is  also  placed  a  little    hydrofluoric  acid,  to  which  the  yeast  has  been  previously 
"  acclimatised  ")  serves  to  pitch  a  200-hectolitre  vat  containing  diluted,  non-sterilised 
molasses,  to  which  has  been  added  8  to  10  kilos  of  calcium  hypochlorite,  this  preventing 
the  development  of  heterogeneous  organisms  during  the  first  few  hours  without  damaging 
the  yeast — already  adapted  to  chlorine.     By  means  of  this  vat  two  other  500-hectolitre 
vats  of  similar  diluted  molasses  may  be  brought  into  a  state  of  vigorous  fermentation; 
the  fermentation  takes  place  so  rapidly  (and  this  is  the  most  specific  action  of  these  yeasts) 
that  in  three  days  the  whole  of  the  molasses  is  fermented,  there  being  thus  no  time  for 
the  development  of  extraneous  germs  causing  harmful  secondary  fermentations. 

(b)  The  Effront  process  is  still  more  simple,  and  is  based  on  the  use  of  selected  yeasts 
specially  adapted  to  molasses  worts  and  endowed  with  exceptionally  rapid  fermenting 
properties;  these  yeasts  are  placed  under  such  conditions  (namely,  the  addition  of  resin) l 
that  they  easily  overcome  deleterious  bacteria  and  complete  the  fermentation  before  these 
become  harmful.     To  the  molasses  simply  diluted  with  water  and  not  sterilised  are  added 
these  special  yeasts,  together  with  1  kilo  of  colophony  per  10  hectolitres  of  wort ;  in  three 
days  the  fermentation  is  complete.     In  1903  almost  1,000,000  kilos  of  colophony  were 
used  in  France  for  this  purpose. 

In  general  bottom  fermentation  beer  yeasts  (see  Beer)  give  high  yields  of  alcohol. 

(2)  Alcohol    from    Fruit.     This   is    not    of    great   industrial   importance, 
although  in  certain  districts   and  in  certain  years  it  assumes  considerable 
magnitude.     In  Italy,  dried  figs  of  little  commercial  value,  carobs,  etc.,  are 
used;    and,  in  other  countries,  plums,  apples,  pears,  etc.     These  fruits  often 
give  an  irregular,  and  seldom  a  complete,  fermentation,  owing  to  conditions 
similar  to  those  encountered  with  beet-molasses.     Hence,  as  in  the  latter  case, 
use  is  made  of  very  active  yeasts  adapted,  where  possible,  to  these  special 
worts. 

The  alcohol  obtained  from  these  worts  has  a  characteristic  odour  indicating 
its  origin. 

(3 )  Alcohol  from  Woody  Substances.    This  is  a  subject  which  has  aroused  considerable 
interest  during  about  the  last  twenty- five  years.     Many  attempts  have  been  made  to 
transform  a  part  of  the  wood  (sawdust,  peat,  etc.)  into  fermentable  sugar  by  the  action 
of  acids  (HF,  S02,  H2S04,  etc.,  at  170°  and  16  atmos.  pressure)  on  the  matter  (lignin) 
encrusting  the  wood  and  not  on  the  cellulose.     In  Chicago  the  process  was  applied  on  a 

1  Effront  observed  that  the  law  of  the  strongest,  which  is  often  verified  in  bacteriology — the 
most  numerous  and  powerful  bacteria  rendering  life  impossible  to  weaker  ones— scarcely  ever 
holds  in  the  case  of  alcoholic  fermentation,  where,  even  though  the  harmful  bacteria  are  less 
numerous  than  the  yeasts,  the  latter  are  seldom  victorious,  the  bacteria  often  entirely  arresting 
alcoholic  fermentation  even  when  the  conditions  are  favourable  for  the  latter. 

According  to  Effront,  this  is  owing  to  the  different  specific  gravities  possessed  by  yeasts  and 
bacteria,  which  hence  live  in  different,  relatively  distant  strata,  so  that  there  is  no  opportunity 
for  the  application  of  the  law  of  the  strongest — which  consists  in  the  production  by  certain  micro- 
organisms of  poisonous  substances  preventing  other  forms  from  developing.  Effront  hence 
proposes  to  add  suitably  emulsified  resin  (colophony )  to  the  worts  at  the  beginning  of  the  fermen- 
tation; this  has  the  property  of  coagulating  only  the  bacteria,  which  become  denser  and  are 
brought  into  more  intimate  contact  with  the  yeast,  the  latter  then  being  in  the  most  favourable 
condition  for  tho  annihilation  of  the  bacteria.  The  resin  itself  is  not  the  cause  of  the  death  of 
the  bacteria,  as  Effront  states  that  these  may  be  readily  cultivated  in  the  pure  state  in  presence 
of  resin  (private  communication). 


168  ORGANICCHEMISTRY 

vast  industrial  scale  according  to  A.  Classen's  patents    (Ger.  Pats.  130,980,  1899,  and 
161,644,  1904).1      100  kilos  of  wood  (with  25  per  cent,  of  moisture)  are  treated  in  an 

1  As  early  as  1820,  Braconnot  observed  that  sugar  is  formed  when  wood  or  even  cotton  cloth 
is  treated  with  sulphuric  acid.  Later  on  Melsens  obtained  a  good  yield  by  treating  cellulose 
with  dilute  sulphuric  acid  in  an  autoclave  under  pressure.  In  1860  Pettenkofer  investigated 
this  process  and  showed  that  it  could  not,  at  that  time,  compete  with  the  use  of  potatoes.  Still 
later,  Basset  prophesied  a  yield  of  32  per  cent,  of  alcohol  from  the  similar  treatment  of  wood  (!). 
Simonsen,  in  1889,  treated  wood  under  pressure  with  dilute  sulphuric  acid  (100  parts  of  water, 
16  of  wood,  and  0-5  of  sulphuric  acid  at  180°  for  two  hours),  transforming  25  per  cent,  of  it  into 
sugar  (78  per  cent,  of  which  was  fermentable)  and  obtaining  a  practical  yield  of  6  to  7  litres  of 
pure  alcohol ;  no  industrial  plant  was,  however,  erected. 

Reiferscheidt  (1905)  overcame  the  resistance  of  the  wood  to  penetration  by  liquid  acid  (met 
with  also  by  Classen)  by  causing  sawdust  to  absorb  two-thirds  of  its  weight  of  sulphuric  acid 
(sp.  gr.  1-65)  and  subjecting  the  mass  to  the  maximum  pressure  of  a  hydraulic  press ;  simple 
digestion  of  the  mass  with  water  and  filtration  gave  a  fermentable  liquid  and  a  yield  of  6*5  per 
cent,  of  alcohol  on  the  weight  of  wood  (pine,  containing  53  per  cent,  of  cellulose)  taken.  A 
similar  yield  is  obtained  by  treating  the  wood  with  five  times  its  weight  of  1  per  cent,  sulphuric 
acid  solution  at  a  pressure  of  8  atmos.  for  fifteen  minutes.  He  confirmed  the  observation  that 
the  pentosans  of  the  wood  do  not  ferment,  and  with  pure  cotton  he  obtained  as  much  as  12  per 
cent,  of  alcohol. 

The  use  of  concentrated  sulphuric  acid  (66°  Be.)  in  the  cold  has  also  been  suggested,  a  yield 
of  more  than  10  per  cent,  of  alcohol  (  ?)  being  claimed.  Experiments  have  likewise  been  made 
on  the  treatment  of  wood  in  the  hot  with  solutions  of  aluminium  chloride,  which  at  100°  to  105° 
dissociates  with  production  of  HC1,  this  converting  the  cellulose  into  dextrin  and  then  into 
fermentable  dextrose. 

According  to  Th.  Korner,  the  addition  of  oxidising  agents  or  of  ozone,  as  was  suggested  by 
Roth  and  Gentzen  (Ger.  Pat.  147,844,  1905),  is  of  no  advantage.  He  obtained  the  best  yields 
by  heating  sawdust,  straw,  etc.,  with  0-5  per  cent,  sulphuric  acid  for  two  hours  in  an  autoclave 
at  6  to  8  atmos. ;  only  a  small  part  of  the  molecular  complex  of  the  cellulose  is  converted  into 
fermentable  sugar,  and  he  obtained  a  yield  of  alcohol  equal  to  15  to  18  per  cent,  of  the  weight  of 
the  true  cellulose  in  the  wood.  Without  the  addition  of  sulphuric  acid,  the  yield  was  about 
one-fourth  less. 

F.  Ewen  and  H.  Tomlinson,  of  Chicago  (U.S.  Pat.  938,308,  1909),  treated  400  kilos  of  sawdust, 
straw,  or  stems  of  various  cereals  (with  30  per  cent,  of  moisture)  in  autoclaves  with  5  kilos  of 
sulphuric  acid  of  60°  Be.  diluted  with  20  litres  of  water;  after  complete  digestion  and  agitation 
the  temperature  of  the  mass  is  brought  in  fifteen  minutes  to  135°  to  160°  by  means  of  steam 
under  pressure ;  after  half  an  hour  the  temperature  is  lowered  rapidly  to  100°  by  allowing  the 
steam  to  escape,  and  the  sulphuric  acid  then  separated  in  the  usual  way.  By  this  means  20  to 
30  per  cent,  of  the  weight  of  the  cellulose  is  transformed  into  fermentable  sugar.  Later,  part  of 
the  sulphuric  acid  was  replaced  by  sulphurous  acid  (1  per  cent,  on  the  weight  of  wood).  A 
similar  process  is  that  of  Eckstrom  (Norw.  Pat.  17,634,  1907).  Willstatter  obtained  better 
results  with  hydrochloric  acid  in  the  cold. 

Classen's  process,  which  has  been  tried  on  a  large  scale  in  North  America,  has  exhibited 
various  disadvantages  :  the  time  required  for  treating  2  tons  of  wood  was  as  much  as  six  hours, 
the  consumption  of  sulphuric  acid  was  large,  part  of  the  sugar  was  destroyed,  and  frequent 
repairs  were  necessary.  The  process  was  improved  by  Ewen  and  Tomlinson,  and  was  worked 
by  the  Standard  Alcohol  Company  in  a  works  at  Georgetown,  S.  Carolina,  and  then  by  the  firm 
E.  J.  Du  Pont  de  Nemours.  Less  acid  was  used  and  the  treatment  maintained  only  for  forty 
minutes,  the  autoclave  being  rota  table  and  made  of  steel  protected  outside  with  fireclay.  This 
was  filled  with  sawdust,  sulphur  dioxide  (1  part  per  100  of  dry  wood)  being  then  passed  in,  and 
subsequently  steam  at  7  atmos.  After  forty  minutes,  the  vapours  of  water,  acetic  acid,  terpenes, 
and  sulphur  dioxide  are  passed  into  washing  or  absorption  Vessels,  while  the  residual  darkened 
sawdust  is  extracted  with  hot  water :  the  aqueous  extract  is  neutralised  with  chalk,  filtered, 
fermented,  and  distilled.  Rectification  yields  94  per  cent,  alcohol  free  from  methyl  and  higher 
alcohols,  and  containing  only  traces  of  furfural  and  other  aldehydes.  The  cost  of  this  alcohol 
seems  to  be  less  than  three-halfpence  per  litre  of  90  per  cent,  concentration. 

Of  the  different  works  which  attempted  the  manufacture  of  alcohol  from  wood  the  only  one 
remaining  at  work  in  the  United  States  in  1913  was  that  at  Georgetown,  where  200  tons  of  saw- 
dust and  wood  waste  from  three  neighbouring  sawmills  was  treated  daily ;  the  yield  of  anhydrous 
alcohol  amounted  to  6000  litres  per  day  (i.  e.,  about  3  per  cent.),  and  even  with  the  Simonsen 
process  the  yield  did  not  exceed  5  per  cent.  However,  the  process  was  further  modified  by  a 
return  to  Simonsen's  system,  but  with  less  water  and  acid,  the  pulp  obtained  being  subjected 
to  diffusion  and  the  sugar  solution  thus  formed  fermented,  a  liquid  containing  2-5  per  cent,  of 
alcohol  resulting. 

J.  Ville  and  W.  Mestrezat  (1910)  state  that,  whilst  cellulose  resists  dilute  solutions  (up  to 
30  per  cent. )  of  hydrofluoric  acid,  with  50  per  cent,  solutions,  100  grams  of  cellulose  yield  50  grams 
of  glucose  ! 

There  has  been  much  discussion  recently  (1906-1907)  concerning  a  process  for  extracting 
spirit  from  peat  in  a  manner  similar  to  that  described  for  wood.  These  attempts  date  from  1870, 
and  various  patents  were  filed  in  1882-1891.  The  most  important  tests  were  made  in  Norway 
in  1906  by  the  Reynaud  process  (1903),  in  which  300  kilos  of  peat  were  treated  in  the  hot  with 
700  kilos  of  water  containing  7  kilos  of  sulphuric  acid  (66°  Be.)  under  3  atmos.  pressure; 
600  litres  of  liquid  were  thus  obtained  and  this  was  fermented  with  specially  selected  yeasts 


ALCOHOL    FROM    PAPER-MILL    LIQUORS     169 

autoclave  for  an  hour  with  about  100  kilos  of  aqueous  sulphur  dioxide  and  sulphuric  acid 
in  presence  of  steam  at  6  to  7  atmos.  pressure  (150°  to  165°).  The  excess  of  sulphur  dioxide 
is  eliminated  by  means  of  a  current  of  air,  the  residue  being  boiled  with  water  or  extracted 
in  diffusers,  and  the  liquid  neutralised  with  calcium  carbonate  and  fermented.  It  is  stated 
that  wood  thus  yields  a  product  containing  35-36  per  cent,  of  solid  residue,  34-63  per  cent, 
of  water,  10-97  per  cent,  of  fermentable  reducing  sugar,  3-21  per  cent,  of  non-fermentable 
reducing  sugars  (pentoses  :  xylose,  etc. ),  0-35  per  cent,  of  sulphuric  acid,  and  0-77  per 
cent,  of  other  acids,  and  it  was  hoped  to  obtain  about  8  litres  of  alcohol  (per  100  kilos  of 
wood)  mixed  with  a  little  acetic  and  formic  acids,  the  residues  being  in  part  utilisable  for 
making  paper.  The  actual  yields  did  not,  however,  correspond  with  expectations.  Host 
and  Wilkening  (1910)  improved  the  Flechsig  process  (1883)  by  treating  5  parts  of  cellulose 
first  with  50  parts  of  72  per  cent,  sulphuric  acid  at  20°  for  three  hours,  then  diluting  with 
water  to  obtain  a  clear  solution  with  an  acidity  of  3  per  cent.,  and  heating  this  in  an  auto- 
clave at  120°  for  two  hours ;  in  this  way  a  yield  of  dextrose  equal  to  90  per  cent,  of  the 
theoretical  yield  was  obtained  and,  after  fermentation,  the  corresponding  amount  of 
alcohol.  In  France,  England,  the  United  States  and  Canada,  there  has  been  an  uninter- 
rupted series  of  trials  and  failures  during  the  past  twenty  years,  some  of  the  industrial 
processes  being  apparently  based  on  speculation  and  hence  certain  of  failure. 

Woods  of  all  kinds  give  the  same  yield  of  alcohol,  with  the  exception  of  oak,  which 
gives  less  owing  to  its  content  of  tannin;  the  latter  should  therefore  be  eliminated 
beforehand. 

(4)  ALCOHOL  FROM  THE  SULPHITE  LIQUORS  OF  PAPER  WORKS.   According 
to  the  Swedish  patents  of  J.  H.  Vallin  and  of  Eckstrom,  alcohol  is  obtained  by  treating 
the  waste  sulphite  liquors  of  paper-mills  in  the  hot  with  sulphuric  acid  and  fermenting  the 
liquid  containing  the  glucose  formed.     The  hot  acid  liquid  has  to  be  neutralised  almost 
completely  with  chalk  and  decanted,  the  residue  being  then  pressed  in  a  filter-press ;  the 
liquid  is  then  cooled  on  piles  to  30°,  pitched  with  yeast,  aerated  during  fermentation  (five 
to  six  hours)  and  the  dilute  alcoholic  liquid  (0-7  to  0*8  per  cent,  alcohol)  distilled.     From 
10  cu.  metres  of  the  sulphite  liquors  are  obtained  60  litres  of  100  per  cent,  alcohol  (which 
is,  however,  of  bad  flavour  and  is  used  for  denaturation).     For  a  factory  producing  60  tons 
of  cellulose  per  day,  i.  e.,  600  tons  of  waste  sulphite  liquors,  the  cost  of  tanks,  pumps, 
piles,  distilling  apparatus,  filter-presses,  etc.,  may  be  taken  as  about  £6000,  and  the  alcohol 
produced  (36  hectolitres  per  day)  would  cost  (including  all  expenses,  but  excluding  taxation) 
10s.  to  11s.  per  hectolitre  at  100  per  cent,  strength.     The  problem  of  the  disposal  of  the 
waste  liquors  (which  contaminate  the  rivers)  of  paper-mills  is  not,  however,  solved  in  this 
way,  since  the  liquid  still  contains  much  decomposable  organic  matter  after  the  distillation 
of  the  alcohol. 

In  1910  there  were  two  factories  in  Sweden  for  the  manufacture  of  alcohol  from  these 
waste  sulphite  liquors  :  that  at  Billingfors  prepared  methyl  alcohol  (15  kilos  per  ton  of  wood 
pulp)  by  H.  Bergstrom  and  H.  Fahl's  process;  the  other  at  Skutskur  manufactured  ethyl 
alcohol.  For  every  ton  of  cellulose  there  are  obtained  8  to  9  tons  of  sulphite  liquors 
containing,  either  dissolved  or  suspended,  as  much  as  12  per  cent,  of  organic  substances, 
and  yielding  alcohol  at  less  than  l%d.  per  litre.  These  yields  and  costs  were  confirmed  in 
1911  at  the  Spritfabrick  Kopmanholmen,  without  allowing  for  the  recovery  of  lime  and 
sulphur  from  the  residues.  In  1912,  three  large  Swedish  sulphite  cellulose  works,  using 
a  modified  process  by  G.  Ekstrom,  produced  altogether  20,000  hectolitres  of  anhydrous 
alcohol  in  the  year.  According  to  Rinman's  process,  based  on  the  dry  distillation  of  the 
residues  from  the  sulphate  treatment  of  cellulose,  it  appears  possible  to  obtain  acetone, 
together  with  a  little  methyl  and  ethyl  alcohols.  During  the  European  War,  Sweden  sold 
considerable  quantities  of  this  alcohol  at  high  prices  to  the  belligerent  nations.  In  normal 
times,  however,  owing  to  the  enormous  bulk  of  the  very  weak  alcoholic  liquid  (0-7  per 
cent. ),  the  high  cost  of  plant,  and  the  large  consumption  of  fuel  necessary,  such  a  process 
is  workable  only  in  countries  where  the  conditions  are  exceptionally  favourable. 

(5)  Alcohol  from  Wine,  Lees,  Vinasse,  and  Withered  Grapes.    In  seasons  when  wine 

(Saccharomiices  ellipsoideus},  the  yield  being  25  litres  of  buoling  spirit  at  an  inclusive  cost  of 
about  4-5cZ.  per  litre,  which  is  about  double  the  cost  of  that  obtained  from  ordinary  starchy 
materials.  In  1905,  the  Danish  Government  offered  a  prize  for  the  improvement  of  this  process, 
but  the  yield  was  not  increased,  although  it  varies  somewhat  (6  to  8  per  cent.)  with  the 
quality  of  the  peat ;  in  all  cases  the  alcohol  obtained  in  this  way  is  too  costly. 


170 


ORGANIC    CHEMISTRY 


is  abundant  and  prices  low  and  in  general  when  there  are  spoilt  wines  (at  6s.  to  8s.  per 

hectolitre),  it  is  convenient  to  extract  the  alcohol  from  them,  this  being  of  use  in  the 

preparation  of  liqueurs  and  spirits. 

The  distillation  presents  no  difficulty  and  is  carried  out  either  in  the  large  distilleries 

or  with  a  Guillaume- Egrot  apparatus  (see  p.  163),  which  is  mounted  on  a  car  so  as  to  be 

readily  transportable,  and  may  be  used  in  places  where  there  is  little  available  water,  since 

the  coolers  and  condensers  act 
as  heaters  and  are  fed  with  the 
wine  to  be  distilled.  It  gives 
directly  90  to  94  per  cent, 
alcohol. 

In  the  same  way  as  wine, 
fresh  lees  or  bottoms  from  wine 
vats  (containing  4  to  6  per  cent, 
of  alcohol)  and  dried  grapes x 
are  treated. 

The  distillation  of  vinasse, 
containing  2-25  to  3-5  per  cent, 
of  alcohol,  is  of  considerable 
importance  in  Italy ;  if  this  were 
all  distilled  it  would  yield  about 
250,000  hectolitres  of  pure 
alcohol  annually  (for  a  produc- 
FIG.  142.  tion  of  40  million  hectolitres  of 

wine).     Of    the    various    forms 

of  apparatus  for  the  distillation  of  vinasse  only  those  of  Villard-Rottner  and  of  Egrot  will 

be  described,  as  they  are  the  commonest  and  differ  little  from  other  good  types. 

The  generator,  K  (Fig.  142),  of  the  Villard-Rottner  apparatus  sends  steam  from  the 

dome,  M,  into  the  three  boilers,  A,  in  succession,  the  steam  entering  at  the  bottom  and 

issuing  at  the  top  of  each.     These  three  boilers  contain  the  vinasse  mixed  with  an  equal 

volume  of  water.     The  vapours,  which  are  rich  in  alcohol,  pass  through  the  pipe,  E,  to 

the  dephlegmator,  G,  and  are  then  condensed  in  the  coil,  I,  at  a  concentration  little  exceeding 

50    per    cent.     When   the    first    boiler    is 

exhausted  it  is  emptied  and  again  charged, 

the  steam  passing  meanwhile  through  the 

second    and   third;    the    first    boiler    now 

becomes  the  third,  the  second  being  then 

emptied,  so  that  two  boilers  are  always  in 

use.     The    hot    water   from  the  boilers   is 

treated    separately    for    the    extraction    of 

tartar  (see  this). 

In  the  Egrot  apparatus   (Fig.   143)  the 

boilers,  A,  are  arranged  on  pivots,  so  that 

they  can  be  inverted  and  rapidly  emptied. 

Steam   from    the    boiler,    D,    extracts    the 

alcohol   from  the   three  boilers,  which  are  -p       ,,o  • 

arranged  in  series,  as  before,  so  that  two 

are  always  in  use  while  the  third  is  being  emptied  and  recharged.     The  alcohol  vapours 

pass  into  the  dephlegmator,  B,  and  thence  into  the  spherical  rectifier,  C ;  R  acts  as  a 

condenser  and  is  cooled  by  water  from  the  tank,  K.     The  condensed  alcohol  passes  along 

1  In  some  countries — at  certain  times  in  Italy — dried  grapes  are  used  for  the  production  of 
alcohol,  especially  Greek  grapes,  which  are  received  from  viticulturists  by  the  Greek  Govern- 
ment in  payment  of  taxes,  and  are  dried  and  placed  on  the  European  markets.  These  grapes 
are  first  macerated  in  tepid  water,  then  crushed  and  fermented  in  the  usual  way;  the  wine 
obtained  may  be  used  for  mixing  with  other  wines  or  for  distillation.  In  1905-1907,  in  order 
to  help  the  crisis  in  the  South,  the  Italian  Government  granted  a  considerable  rebatement  of 
taxation  on  the  alcohol  obtained  from  grapes.  The  Italian  distillers  then  began  to  import  large 
quantities  of  Greek  grapes  (containing  50  to  55  per  cent,  of  sugar),  which  could  be  delivered  in 
the  factory  at  about  £6  10s.  per  ton,  so  that  the  southern  viticulturists  reaped  no  advantage 
from  the  rebate,  which  was  hence  abolished. 


SYNTHETIC    ALCOHOL  171 

the  tube,  m,  to  the  test-glass,  M,  and  from  there  to  the  casks,  t,  at  a  concentration  of  55 
to  60  per  cent. 

With  the  first  apparatus,  to  treat  10  tons  of  vinasse,  yielding  about  8  hectolitres  of  brandy 
at  51  per  cent.,  roughly  26  cwt.  of  coal  are  consumed,  whilst  the  Egrot  apparatus  uses 
much  less  than  this  for  an  equal  yield.  The  brandy  thus  obtained  has  almost  always  a 
rather  unpleasant  flavour,  and  is  often  used  for  rectification  in  the  ordinary  way  (if  too 
dilute  it  becomes  opalescent),  and  is  then  left  to  age  in  oak  casks  so  as  to  acquire  a  pleasing 
aroma.  This  result  is  obtained  more  rapidly  by  pasteurisation,  that  is,  by  passing  the 
brandy  through  a  coil  surrounded  by  water  at  60°  to  65°,  or  by  passing  a  current  of  ozonised 
air  through  it  (artificial  maturation).  The  name  cognac  is  given  to  the  finest  old  French 
brandies. 

Alcohol  from  cereals  may  be  distinguished  from  that  obtained  from  wine,  etc.,  as  the 
latter  always  contains  aldehydes  (see  later,  Rimini's  Reaction  and  Schiff  s  Reagent). 

(6)  Alcohol  from  Green  Maize.    Use  has  been  made  in  the  United  States  of  the  Stewart 
process,  according  to  which  the  cobs  are  removed  from  the  maize  plants  when  the  grain 
has  attained  a  milky  consistency.     The  remaining  plants  continue  to  grow  and  become 
exceptionally  rich  in  sugar,  it  being  possible  to  obtain  per  hectare  (247  acres)  13  tons  of 
sugar  and,  by  fermenting  the  milky  mass  of  the  seeds  (which  contain  20  per  cent,  of  fer- 
mentable matter),  about  2000  litres  of  alcohol,  the  residual  cake  having  a  high  nutritive 
value. 

(7)  Alcohol  from  Calcium  Carbide  (Synthetic  Alcohol).     From  the  ethylene  present 
in  illuminating  gas  and  in  oil-gas,  Hennel,  a  collaborator  with  Faraday,  obtained  (1825-1828) 
ethylsulphuric  acid  (sulphovinic  acid),  which  on  decomposition  yielded  alcohol.     Berthelot 
studied  this  reaction  more  in  detail  in  1855,  and  Fritzsche  in  1897,  and  more  thoroughly  in 
1912,  established  the  conditions  for  obtaining  the  maximum  yield  of  alcohol :  C2H4  -+- 
H2S04  =  C2H5O  •  S03H   and   the   latter  +  H20  =  C2H5-OH  +  H2SO4;  100  kilos  of   hot 
concentrated  sulphuric  acid  absorb  14  kilos  of  ethylene,  18  kilos  of  100  per  cent,  alcohol 
being  obtainable.     The  ethylene  may  be  derived  from  coal-gas  or  by  reduction  of  acetylene 
by  means  of  hydrogen.     A  very  large  quantity  of  acid  (450  kilos  per  hectolitre  of  alcohol) 
must  be  put  into  circulation,  and  this  is  not  all  recovered,  and,  further,  requires  reconcen- 
tration.     Acetylene  may  give  alcohol  also  directly  (Jay  et  Cie.,  Paris,  Ger.  Pat.  149,893, 
1902)  by  treating  it  with  hydrogen  and  ozonised  oxygen  at  20°  to  55°  and  condensing  the 
small  amount  of  aldehyde  formed  with  ammonia. 

In  1907,  Jonas,  Desmonts,  and  Deglotigna  (Fr.  Pat.  360,180)  proposed  preparing 
alcohol  by  first  dissolving  acetylene  in  mercurous  nitrate  and  then  heating  the  mass  to 
boiling ;  the  precipitate  decomposes,  regenerating  the  mercury  salt  and  evolving  vapours 
of  acetaldehyde,  which  are  condensed  and  converted  into  alcohol  by  means  of  sodium 
amalgam  (nascent  hydrogen).  Further,  the  Griesheim-Elektron  Company  and  N.  Grim- 
stein  (Ger.  Pats.  250,356,  253,707,  261,589  and  267,260,  1910-1912,  and  Fr.  Pat.  440,658) 
succeeded  in  preparing  acetaldehyde  in  good  yield  by  passing  acetylene  into  a  sulphuric 
acid  solution  of  mercury  nitrate  kept  at  15°  to  25°,  an  atmosphere  of  acetylene  being  main- 
tained at  the  surface,  while  superposed  on  the  liquid  is  a  solvent  which  dissolves  the  alde- 
hyde as  it  forms  and  thus  prevents  it  from  polymerising ;  the  same  end  may  be  attained 
by  causing  separation  of  the  aldehyde  by  dissolving  sodium  sulphate. in  the  mass  or  by 
occasional  distillation  of  the  aldehyde.  Transformation  of  the  aldehyde  into  acetic  acid 
or  alcohol  appears  to  be  easy  and  to  give  good  yields. 

Shortly  before  the  outbreak  of  the  European  War  the  Lonza  Company  of  Vallese 
(Switzerland)  erected  a  works  for  the  large  scale  manufacture  of. acetic  acid  and  anhydride 
from  acetylene  by  a  process  analogous  to  that  of  the  Griesheim-Elektron  Company ;  they 
attempted  also  to  produce  synthetic  alcohol.  Messrs.  Dreyfus  of  Basle  likewise  succeeded 
in  preparing  acetic  acid,  acetic  anhydride  and  alcohol  from  acetylene,  and  during  the  war 
built  three  large  plants — in  Italy,  France,  and  England;  these  were,  however,  failures, 
and  seem  to  be  speculations  on  the  part  of  unscrupulous  bankers  and  business  men.  A 
painful  and  clamorous  echo  of  this  entanglement  of  more  than  £4,000,000  was  heard  in 
the  House  of  Commons  early  in  1918. 

Prior  to  the  war,  alcohol  from  grain  cost  about  £14  per  ton,  whilst  that  from  acetylene 
cost  at  least  £22,  2000  kilos  of  calcium  carbide  and  500  cu.  metres  of  hydrogen  being  required, 
without  taking  into  account  the  sulphuric  acid  and  catalyst  lost,  the  coal,  patent  rights, 
and  sinking  fund  for  such  colossal  plant. 


172 


ORGANIC    CHEMISTRY 


REFINING  AND  PURIFICATION  OF  SPIRIT.  After  the  introduction  of  rational 
methods  of  fermentation  with  selected  yeasts  and  of  more  perfect  rectifying  appliances, 
the  quantity  of  actual  alcohol  was  considerably  increased  and  it  was  generally  sufficiently 
pure  for  ordinary  commercial  purposes.  When,  however,  it  became  recognised  that  the 
harmful  effects  of  alcoholism  are  aggravated  by  the  presence  in  commercial  alcohols  for 
liquors,  etc.,  of  even  minimal  quantities  of  aldehydes  and  amyl  alcohol,  recourse  was  some- 
times had  to  a  special  purification  or  refining  of  rectified  spirits  in  order  to  give  them  a  slight 
ethereal  odour,  which  is  greatly  valued.  Of  the  many  and  varied  substances  suggested 
for  the  purification,  mention  need  only  be  made  of  wood  charcoal  in  lumps  calcined  and 
cooled  out  of  contact  with  air  and  placed  in  batteries  of  tall  iron  cylinders  through  which 
the  alcohol  is  passed ;  when  the  charcoal  becomes  inactive  it  is  revivified  by  means  of  super- 
heated steam  at  600°.  The  charcoal  has  an  oxidising,  esterifying,  and  decolorising  action, 
but  it  does  not  fix  the  amyl  alcohol.  Treatment  with  fatty  oils  (which  retain  the  aldehydes ) 
and  subsequent  distillation  are  also  used,  as  also  is  addition  of  carbonates  of  the  alkalis  and 
alkaline  earths.  Treatment  with  oxidising  agents — ozonised  air,  potassium  permanganate 
or  dichromate,  nitric  acid,  chloride  of  lime,  etc. — has  the  disadvantage  of  forming  acetic 
acid  and  ethyl  acetate.  Consequently  Naudin  prefers  reducing  the  aldehydes  with  nascent 
hydrogen  formed  in  the  liquid  itself  by  means  of  a  copper-zinc  couple. 

R.  Pictet  has  devised  a  totally  different  process  :  owing  to  the  variations  (at  different 
temperatures)  of  the  maximum  vapour  pressure  of  volatile  liquids,  he  ascertained  that 
the  vapours  obtained  from  a  mixture  of  water  or  other  substances  with  alcohol  are  the 
richer  in  alcohol  the  lower  the  temperature  to  which  the  mixture  is  heated.  He  boils  the 
mixture  at  50°  to  60°  in  a  vacuum  and  then  rectifies  the  vapours  in  a  column  at  a  tempera- 
ture of  —  30°  or  —  40°,  obtained  by  means  of  a  sulphur  dioxide  refrigerating  machine. 
The  apparatus  is  somewhat  complex,  but  it  yields  a  well-refined  pure  spirit.1 

1  Tests  for  the  Purity  of  Alcohol.    The  tests  mentioned  on  p.  131  will  detect  traces  of 

water  in  so-called  absolute  alcohol. 

If  alcohol  is  highly  purified  (puriss.),  10  c.c.  of  it,  mixed  with  1  c.c.  of  water  and  1  c.c.  of  0-1  per 

cent,  potassium  permanganate  solution,  should  retain  its  red  colour  for  twenty  minutes, 
or  for  at  least  five  minutes  if  the  alcohol  is  termed  pure  ;  it  should  not  become 
turbid  on  dilution  with  water,  should  give  neither  an  acid  nor  an  alkaline  reaction 
(with  phenolphthalein),  and  should  remain  unchanged  with  ammoniacal  silver 
nitrate  solution.  To  test  for  aldehyde  the  alcohol  is  diluted  with  water  and  a  few 
drops  distilled  and  tested  by  Rimini's  reaction  (see.  p.  131);  or,  for  aldehydes  in 
general,  by  Schiff' s  reagent  (fuchsine  solution  decolorised  with  sulphur  dioxide  : 
0-5  gram  of  fuchsine  is  dissolved  in  500  c.c.  of  water  and  decolorised  with  10  c.c. 
of  sodium  hydrogen  sulphite  solution  of  sp.  gr.  1-26  and  10  c.c.  of  concentrated 
HC1);  a  few  cubic  centimetres  of  this  reagent  are  coloured  red  when  shaken  with 
a  few  drops  of  alcohol  containing  traces  of  aldehydes. 

Of  more  importance  is  the  quantitative  estimation  of  the  fusel  oil  (see  Note, 
p.  165). 

Traces  of  fusel  oil  may  be  detected  by  Kamarowsky's  reaction,  i.  e.,  with 
salicylic  aldehyde  and  sulphuric  acid;  H.  Kreis's  modification  (1907)  of  this 
colorimetric  reaction  yields  moderately  accurate  results.  In  the  commercial 
control  of  the  purity  of  alcohol  use  is  generally  made,  for  the  quantitative 
estimation  of  the  fusel  oil,  of  Herzfeld  and  Windisch's  modification  of  Rose's 
apparatus  (Fig.  144);  the  method  is  based  on  the  property  possessed  by 
chloroform  of  dissolving  the  higher  alcohols  and  a  very  little  ethyl  alcohol,  at  the 
same  time  increasing  in  volume.  The  alcohol  is  first  diluted  very  exactly  to  a 
concentration  of  30  per  cent,  by  volume,  or,  better,  to  the  sp.  gr.  0-9657  at  15-5° 
(see  Table,  p.  177 ;  if  the  alcohol  has  a  concentration,  v,  less  than  30  per  cent., 


then 


10(30  -  v) 


c.c.  of  absolute  alcohol  should  be  added ).    The  Rose  tube  (washed 


with  alkali,  acid,  water,  alcohol,  and  ether  and  well  dried)  has  a  cylindrical 
expansion  at  the  bottom  containing  20  c.c.  up  to  the  first  mark ;  then  comes  a 
tube  18  cm.  long,  holding  2-5  c.c.  and  graduated  in  0-01  c.c.;  at  the  top  is  a 
pear-shaped  bulb  of  about  200  c.c.  capacity,  closed  with  a  ground  stopper.     The 
tube  is  placed  in  water  at  15°  and  into  it  arc  introduced  by  a  long  funnel  reaching 
to  the  lower  bulb  20  c.c.  of  pure  chloroform  at  15°,  and  then  100  c.c^of  the 
alcohol  diluted  to  30  per  cent,  at  15°  and  1  c.c.  of  sulphuric  acid  of  sp.  gr?"  1-2857 
(38  per  cent.  H2S04).     The  tube  is  then  closed,  inverted  so  that  all  the  liquid 
FIG.  144.        passes  into  the  pear-shaped  bulb,  shaken  vigorously  for  a  minute  (150  shakes) 
and  placed  erect  in  the  water-bath  at  15°,  where  it  is  left  for  fifteen  minutes 
after  a  rotatory  movement  has  been  imparted  to  the  liquid  so  as  to  collect  the  drops  of 
chloroform  adhering  to  the  walls.    The  increased  volume  of  the  chloroform  is  then  compared 
with  that  obtained  in  a  similar  test  with  pure  alcohol  of  the  same  concentration.     If  no  blank 
experiment  is  made,  1-64  c.c.  is  subtracted  from  the  increase  in  volume  as  being  due  to  the 


ALCOHOL    METERS 


173 


ALCOHOL  METERS  OR  MEASURES.  These  are  important  instruments,  as  in 
nearly  all  countries  the  manufacture  of  alcohol  is  subject  to  taxation  which  is  calculated 
on  the  quantity  of  alcohol  passing  through  a  sealed  meter  indicating  automatically  the 
corresponding  amount  of  pure  alcohol  (100  per 
cent. ).  The  Siemens  measurer  is  the  one  most 
commonly  used  (Figs.  145  and  146),  and  some- 
what resembles  the  gas-meter  (see  p.  56) 


FIG.  145. 


Fio.  146. 


even  in  its  registration.  The  alcohol,  which  enters  laterally  by  the  tube  I,  is  discharged 
into  the  inner  central  part  of  the  drum,  B,  i.  e.,  into  D,  this  being  divided  longi- 
tudinally into  three  small  chambers  furnished  with  apertures,  r1,  r2,  r3;  when  the  small 

ethyl  alcohol  dissolved.  Each  0-01  c.c.  increase  in  volume  of  the  chloroform  corresponds  with 
0-006634  per  cent,  by  volume  of  fus,el  oil.  For  an  alcohol  rich  in  fusel  oil  which  gave  a  final 
volume  of  chloroform  of  22-14  c.c.  the  true  increase  in  volume  will  be  22-14  —  1-64  —  20'=  0-5  c.c. 
The  percentage,  /,  of  fusel  oil  by  volume  on  the  original  alcohol  (not  on  that  diluted  to  30  per 
cent. )  is  calculated  by  the  following  formula  : 

t  -  (c-&)  (100  +  a) 
1 "  150 

where  c  is  the  unconnected  increase  in  volume  of  the  chloroform,  b  is  the  correction,  1-64,  due  to 
the  ethyl  alcohol,  and  a  indicates  the  number  of  cubic  centimetres  of  water  or  absolute  alcohol 
added  to  100  c.c.  of  the  original  spirit  to  bring  it  to  30  per  cent.  Example :  If  80  per  cent, 
alcohol  is  used,  171-05  c.c.  of  water  must  be  added  to  100  c.c.  to  break  it  down  to  30  per  cent. ; 
100  c.c.  of  this  then  increases  the  volume  of  the  chloroform  from  20  to  21-94  c.c.,  so  that : 


(1-94  -  1-64)  (100  -{-  171-06) 
150 


=  0-54  per  cent,  by  volume  of  fusel  oil. 


The  furfural  is  determined  in  10  c.c.  of  distilled  alcohol,  to  which  are  added  10  drops  of  colour- 
less aniline  and  2  c.c.  of  acetic  acid ;  if  a  red  coloration  appears  after  twenty  to  thirty  minutes 
furfural  is  present. 

The  estimation  of  small  quantities  of  benzene  in  denatu rated  alcohol  may  be  carried  out  by 
means  of  Rose's  apparatus  (for  more  than  1  per  cent,  of  benzene).  The  best  method  is  to  dilute 
100  c.c.  of  the  alcohol  to  a  concentration  of  24-7  per  cent,  by  weight  and  to  distil  the  whole ;  the 
first  10  c.c.  of  the  well-cooled  distillate  is  diluted  to  20  to  25  c.c.  with  water  in  a  graduated 
cylinder;  the  volume  of  the  benzene  which  separates  is  increased  by  0-3  per  cent.,  which  is  a 
constant  error  of  the  method.  This  method  of  Holde  and  Winterfeld  (1908)  is  based  on  the 
fact  that  when  the  alcohol  is  diluted  with  water,  the  vapour  pressure  of  the  benzene  is 
considerably  augmented,  whilst  that  of  the  alcohol  is  diminished. 

To  ascertain  if  methyl  alcohol  is  present  in  alcohol,  1  c.c.  of  it  is  treated  with  1  c.c.  of  chromic 
acid  solution  and  5  c.c.  of  water,  the  whole  being  then  carefully  distilled  until  only  0-5  c.c. 
remains.  The  distillate  is  condensed  in  a  long,  air-cooled  tube  and  collected  in  a  test-tube, 
the  condenser-tube  being  washed  out  with  2  c.c.  of  distilled  water.  One  drop  of  ferric  chloride 
and  two  of  albumin  solution  are  added  to  the  test-tube,  which  is  shaken ;  5  c.c.  of  concentrated 
sulphuric  acid  is  then  cautiously  added.  The  immediate  appearance  of  a  violet  ring  at  the  zone 
separating  the  two  layers  indicates  that  the  original  alcohol  contained  more  than  5  per  cent, 
of  methyl  alcohol ;  if  the  coloration  appears  after  a  minute,  the  proportion  is  1  to  5  per  cent, 
and  if  after  two  minutes  less  than  1  per  cent.  (A.  Vorisek,  1909).  Another  sensitive  test  is  as 
follows  :  1  c.c.  of  the  spirit  is  shaken  in  a  test-tube  with  5  c.c.  of  1  per  cent,  potassium  perman- 
ganate solution  and  0-2  c.c.  (not  more)  of  pure,  concentrated  sulphuric  acid;  after  a  rest  of 
two  to  three  minutes  the  liquid  is  shaken  with  1  c.c.  of  8  per  cent,  oxalic  acid  solution.  When 
the  mixture  has  assumed  a  brownish -yellow  coloration,  1  c.c.  of  concentrated  sulphuric  acid  is 
added,  decolorisation  then  occurring  in  a  few  seconds.  The  liquid  is  then  mixed  with  5  c.c.  of 
rosaniline  bisulphite  and  allowed  to  stand  :  in  presence  of  ethyl  alcohol  alone  a  greenish  to 
intense  violet  coloration  appears,  this  vanishing  in  a  few  minutes;  with  spirit  containing  as 
little  as  1  per  cent,  of  methyl  alcohol  the  more  or  less  pale  violet  colour  persists  for  several  hours. 


174  ORGANIC    CHEMISTRY 

chamber  is  about  half  full  the  alcohol  falls  into  the  large  lower  chamber  (e.  g.,  I),  which 
has  a  capacity  of  4  litres.  When  this  chamber  is  filled  with  alcohol  the  level  of  the  latter 
reaches  the  chamber  D,  the  alcohol  then  falling  through  r2  into  //  and  displacing  the 
equilibrium,  so  that  the  drum,  B,  is  forced  round  in  the  sense  of  the  arrow.  At  the  same 
time  the  first  4  litres  of  alcohol  is  discharged  into  the  vessel  C,  which  communicates  with 
the  storage  reservoir  by  means  of  the  tube  G.  The  compartment  //  then  occupies  the 
position  of  /,  and  so  on.  The  axis  of  the  drum  is  connected  with  a  suitable  automatic 
registering  device.  At  the  same  time,  in  the  cylinder  A  in  front  of  the  drum,  the  alcohol 
which  passes  through  raises  the  float,  P,  more  or  less  according  to  its  strength,  and  a  screw, 
Q,  operates  the  lever,  T,  and  so  moves  the  index,  8,  the  point  of  which  registers  the  alcoholic 
strength  on  a  paper  ribbon  moving  along  a  carefully  calculated  curve,  X.  In  order  that 
alcohols  of  different  concentrations  may  be  well  mixed  and  so  influence  the  float  correctly, 
they  are  delivered  at  E,  where  there  are  two  tubes ;  one  of  these,  a,  collecting  the  lighter 
alcohol,  rises  and  then  descends  (c),  discharging  into  the  bottom  of  A  by  the  perforated 
tube,  e;  the  denser  alcohol  passes  preferably  along  b  and  is  discharged  through  the  per- 
forated tube,  d,  at  the  top  of  A,  so  that  mixing  is  rapid  and  complete.  The  registration 
is  also  independent  of  the  temperature  of  the  alcohol,  as  its 
expansion  (or  contraction)  is  allowed  for  by  that  of  the  float. 

QUANTITATIVE  ESTIMATION  OF  ALCOHOL  AND 
ALCOHOLOMETRY.  As  a  rule  alcohol  is  sold  by  volume 
and  not  by  weight;  1  litre  of  absolute  alcohol  weighs  0-7937 
kilo  or  1  kilo  measures  1-2694  litres.  Industrially  alcohol  is 
stated  to  be  of  so  many  litre-degrees;  thus  100  litres  of  2  per 
cent,  alcohol  would  contain  200  litre-degrees  (100  X  2),  and  100 
litres  of  50  per  cent,  alcohol  would  indicate  5000  litre-degrees, 
which  would  also  be  given  by  1000  litres  of  5  per  cent,  alcohol; 
so  also  75-48  litres  of  100  per  cent,  alcohol  would  be  expressed 
as  7548  litre-degrees.  Alcohol  is  taxed  on  the  basis  of  the  number 
of  litres  of  absolute  alcohol. 

The  alcohol-content  of  an  aqueous  alcoholic  solution  is  deduced 
from  the  specific  gravity  determined  by  the  Westphal  balance,  or 
„  directly  by  the  Gay-Lussac  alcoholometer  (at  15°)  in  France,  or  by 

the  Tralles  official  alcoholometer  (at  15-56°)  in  Italy  and  Germany, 

these  giving  the  percentage  of  alcohol  by  volume  contained  in  100  vols.  of  the  aqueous 
alcohol.  The  reading  on  the  alcoholometer  is  made  at  the  point  of  the  stem  coincident 
with  the  lower  meniscus,  which  is  well  seen  by  looking  rather  below  the  surface  of  the 
liquid  (Fig.  147);  to  avoid  error,  the  alcoholometer  must  be  so  immersed  that  the  whole 
of  the  graduated  stem  is  not  wetted  (see  Vol.  I.,  p.  78).  To  determine  the  percentage  by 
weight  contained  in  100  vols.  the  percentage  by  volume  is  multiplied  by  0-7939  (specific 
gravity  of  absolute  alcohol)  and  divided  by  the  specific  gravity  of  the  alcohol  examined 
(see  Table  on  p.  175). 

To  correct  the  alcohol  reading  determined  at  a  temperature  different  from  15°  (or 
15-56°  for  the  Gay-Lussac  alcoholometer),  the  following  moderately  exact  formula  of  Fran- 
cceur  is  used :  x  =  c  ^  0-39<,  where  x  is  the  number  of  Gay-Lussac  degrees  at  15°,  c  the 
number  of  degrees  found  at  the  non-normal  temperature,  and  t  the  number  of  degrees 
the  latter  is  above  or  below  15° ;  the  +  sign  of  the  formula  is  used  if  the  temperature  is 
below  15°  and  the  —  sign  if  it  is  above  15°.  Thus  an  alcohol  showing  72°  on  the  Gay- 
Lussac  alcoholometer  at  a  temperature  of  28°  would  have  :  x  =  72  —  0-39  X  13  =  66-93° 
Gay-Lussac  at  15°. 

With  dilute  alcoholic  liquids  of  complex  composition  (wine,  beer,  spirits,  etc.)  the 
alcoholic  degrees  cannot  be  deduced  from  the  specific  gravities.  If,  however,  a  given 
volume,  e.  g.,  100  c.c.,  is  taken  and  distilled  in  the  usual  way  (p.  2)  or  in  the  Salleron 
apparatus  (Fig.  149)  until  all  the  alcohol  has  passed  over  (about  70  c.c.),  the  distillate 
may  be  made  up  to  the  original  volume  with  distilled  water  and  its  specific  gravity  and 
alcoholic  strength  determined  in  the  usual  manner.  In  order  to  prevent  frothing  during 
the  distillation  of  beer  and  wine  a  piece  of  tannin  or  a  few  drops  of  oil  are  added.1 

1  The  original  type  of  the  Salleron  apparatus  used  by  small  wine  merchants  is  that  shown  in 
Fig.  149. 

In  some  cases  the  alcohol  of  wines  and  other  liquors  is  determined  by  the  Geissler  vapori- 
meter,  which  indicates  the  pressure  of  the  vapours  from  the  liquid  heated  at  100°.  By  means 


STRENGTH    OF    AQUEOUS    ALCOHOL      175 

WINDISCH'S  TABLE  FOR  CALCULATING  THE  STRENGTH  OF  AQUEOUS 
ALCOHOL  SOLUTIONS 


Sp.  gr. 

Grams  of 

C.o.  of 

Grams  of 

Sp.  gr. 

Grams  of 

C.c.  of 

Gram?  of 

at 

alcohol  iu 

alcohol  in 

alcohol  in 

at 

alcohol  in 

alcohol  in 

alcohol  in 

15°  0. 

100  grms. 

100  c.c.  ' 

100  c.c. 

15°  0. 

100  grms. 

100  c.c. 

100  c.c. 

0-9999 

0-05 

0-07 

0-05 

0-9550 

31-66 

38-06 

30-21 

0-9992 

0-42 

0-53 

0-42 

0-9535 

32-55 

39-07 

31-01 

0-9985 

0-80 

1-00 

0-80 

0-9520 

33-42 

40-06 

31-79 

0-9978 

1-17 

1-48 

1-17 

0-9505 

34-28 

41-02 

32-55 

0-9970 

1-61 

2-02 

1-60 

0-9490 

35-11 

41-95 

33-30 

0-9963 

2-00 

2-51 

1-99 

0-9470 

36-21 

43-17 

34-26 

0-9956 

2-39 

3-00 

2-38 

0-9455 

37-01 

44-06 

34-96 

0-9949 

2-79 

3-49 

.     2-77 

0-9440 

37-80 

44-93 

35-66 

0-9942 

3-19 

4-00 

3-17 

0-9420 

38-84 

46-07 

36-56 

0-9935 

3-60 

4-51 

3-58 

0-9405 

39-61 

46-90 

37-22 

0-9928 

4-02 

5-03 

3-99 

0-9385 

40-62 

47-99 

38-09 

0-9922 

4-39 

5-48 

4-35 

0-9365 

41-61 

49-06 

38-93 

0-9915 

4-81 

6-01 

4-77 

0-9345 

42-59 

50-11 

39-76 

0-9909 

5-19 

6-47 

5-14 

0-9330 

43-31 

50-88 

40-38 

0-9902 

5-63 

7-02 

5-57 

0-9305 

44-51 

52-14 

41-38 

0-9896 

6-02 

7-50 

5-95 

0-9290 

45-22 

52-89 

.    41-97 

0-9889 

6-48 

8-07 

6-40 

0-9265 

46-39 

54-12 

42-95 

0-9884 

6-81 

8-48 

6-73 

0-9245 

47-32 

55-08 

43-71 

0-9877 

7-29 

9-06 

7-19 

0-9225 

48-24 

56-03 

44-47 

0-9872 

7-63 

9-48 

7-53 

0-9205 

49-16 

56-97 

45-21 

0-9866 

8-05 

10-00 

7-94 

0-9180 

50-29 

58-13 

46-13 

0-9860 

8-48 

10-52 

8-35 

0-9160 

51-20 

59-05 

46-86 

0-9854 

8-91 

11-05 

8-77 

0-9140 

52-09 

59-95 

47-57 

0-9849 

9-28 

11-50 

9-13 

0-9115 

53-21 

61-06 

48-46 

0-9843 

9-72 

12-05 

9-56 

0-9095 

54-10 

61-95  • 

49-16 

0-9838 

10-10 

12-50 

9-92 

0-9070 

55-20 

63-04 

50-03 

0-9832 

10-55 

13-06 

10-36 

0-9050 

56-09 

63-91 

50-71 

0-9827 

10-94 

13-53 

10-74 

0-9025 

57-18 

64-98 

51-56 

0-9822 

11-33 

14-01 

11-12 

0-9000 

58-27 

66-03 

52-40 

0-9817 

11-72 

14-48 

11-49 

0-8975 

59-36 

67-08 

53-23 

0-9811 

12-20 

15-07 

11-96 

0-8955 

60-23 

67-91 

53-89 

0-9807 

12-52 

15-46 

12-27 

0-8930 

61-31 

68-94 

54-71 

0-9801 

13-00 

16-04 

12-73 

0-8905 

62-39 

69-95 

55-51 

0-9796 

13-41 

16-54 

13-13 

0-8880 

63-47 

70-96 

56-31 

0-9791 

13-82 

17-04 

13-52 

0-8855 

64-54 

71-96 

57-10 

0-9786 

14-23 

17-54 

13-92 

0-8830 

65-61 

72-94 

57-88 

0-9781 

14-65 

18-04 

14-31 

0-8805 

66-67 

73-92 

58-66 

0-9776 

15-06 

18-54 

14-71 

0-8775 

67-95 

75-07 

59-57 

0-9771 

15-48 

19-04 

15-11 

0-8750 

69-01 

76-02 

60-33 

0-9766 

15-90 

19-55 

15-51 

0-8725 

70-06 

76-97 

61-08 

0-9761 

16-32 

20-05 

15-91 

0-8695 

71-33 

78-08 

61-97 

0-9756 

16-73 

20-55 

16-31 

0-8670 

72-37 

79-00 

62-60 

0-9751 

17-15 

21-06 

16-71 

0-8640 

73-63 

80-09 

63-56 

0-9747 

17-49 

21-46 

17-03 

0-8615 

74-67 

80-99 

64-27 

0-9741 

17-98 

22-06 

17-50 

0-8585 

75-91 

82-05 

65-11 

0-9736 

18-40 

22-55 

17-90 

0-8555 

77-15 

83-10 

65-94 

•0-9731 

18-81 

23-05 

18-29 

0-8530 

78-17 

83-96 

66-63 

0-9726 

19-22 

23-54 

18-68 

0-8500 

79-40 

84-97 

67-43 

0-9721 

19-63 

24-02 

19-07 

0-8470 

80-62 

85-97 

68-23 

0-9716 

20-04 

24-51 

19-45 

0-8440 

81-83 

86-95 

69-CO 

0-9710 

20-52 

25-08 

19-91 

0-8405 

83-23 

88-08 

69-90 

0-9705 

20-92 

25-56 

20-28 

0-8365 

84-42 

89-02 

70-65 

0-9695 

21-71 

26-50 

21-03 

0-8340 

85-80 

90-09 

71-50 

0-9685 

22-49 

27-42 

21-76 

0-8310 

86-97 

90-99 

72-21 

0-9675 

23-25 

28-32 

22-47 

0-8275 

88-31 

92-01 

73-02 

0-9665 

24-00 

29-20 

23-17 

0-8240 

89-64 

93-00 

73-80 

0-9655 

24-73 

30-06 

23-86 

0-8200 

91-13 

94-09 

74-66 

0-9645 

25-45 

30-91 

24-53 

0-8165 

92-41 

95-00 

75-39 

0-9630 

26-51 

32-14 

25-50 

0-8125 

93-85 

96-00 

76-19 

0-9620 

27-19 

32-93 

26-13 

0-8080 

95-34 

97-08 

77-04 

0-9605 

28-19 

34-10 

27-06 

0-8040 

96-79 

97-99 

77-76 

0-9590 

29-17 

35-22 

27-95 

0-7990 

98-46 

99-05 

78-61 

0-9580 

29-81 

35-95 

28-53 

0-7925 

100-00 

100-00 

79-36 

0-9565 

30-74 

37-02 

29-38 

There  are  also  Tables  by  Hehner,  Haas,  Tralles-Brix,  Gay-Lussac,  etc.,  which  differ  little  (at  most  O'l  to  0'2  per 
cent.)  from  that  of  Windisch. 

For  any  specific  gravity  not  given  in  the  Table  the  corresponding  alcoholic  degree  may  be  obtained  easily  and 
with  sufficient  accuracy  by  proportional  interpolation. 


176 


ORGANIC    CHEMISTRY 


USES  AND  DENATURATION  OF  ALCOHOL.     The  uses  of  alcohol  are  very  varied, 
but  are  sometimes  limited  by  the  high  price  resulting  from  the  taxation,  which  should  be 

of  a  Table  the  alcoholic  strength  may  be  read  off,  knowing  the  vapour  pressure ;  the  latter  is 
measured  on  a  special  barometric  U-tube,  B  (Fig.  148),  to  one  end  of  which  is  fixed  the  bottle, 
0,  containing  mercury  and  the  alcoholic  liquid  and  placed  in  the  jacketed  vessel,  D,  filled  with 
steam  from  the  boiler,  A.  This  apparatus  gives  results  which  are  influenced  by  several  factors 
(dissolved  carbon  dioxide,  salts,  etc.),  so  that  little  use  is  made  of  it.  In  more  general  use  is 
the  ebullioscope  devised  in  1823  by  Groningen  and  subsequently  improved  by  Tabarie  (1833), 
Brossard-Vidal  (1842),  Malligand  (1874),  Salleron  (1880),  and  Amagat  (1885).  Malligand's 
form  (Fig.  150)  is  the  most  commonly  used,  and  is  based  on  the  different  boiling-points  possessed 
by  alcoholic  liquids  of  different  concentrations.  The  reservoir,  F,  is  provided  with  a  cover, 


FIG.  149. 


FIG.  148. 


FIG.  150. 


through'which  pass  a  thermometer,  T,  bent  at  a  right-angle  and  a  tube  surrounded  by  the  con- 
denser, R.  This  cover  is  unscrewed  and  water  poured  into  the  reservoir  as  far  as  the  lower 
mark  inside,  the  cover  being  then  screwed  on  (the  bulb  of  the  thermometer  does  not  touch  the 
water).  The  burner,  L,  is  then  lighted  under  the  small  chamber,  S,  which  is  traversed  by  a 
brass  tube  communicating  with  the  reservoir ;  the  part  a'  being  rather  higher  than  a,  circulation 
of  liquid  takes  place  through  the  tubes  and  reservoir.  When  the  mercury  thread  of  the  ther- 
mometer remains  stationary  owing  to  the  water  boiling  and  the  steam  hence  having  a  constant 
temperature,  the  scale  is  adjusted  by  the  screw,  E,  so  that  the  zero-point  corresponds  with  the 
end  of  the  mercury  column.  The  reservoir  is  then  emptied,  rinsed  out  with  the  wine,  etc. 
(containing  less  than  15  per  cent,  of  alcohol),  and  then  filled  with  the  wine  to  the  upper  mark, 
so  that  the  thermometer  bulb  dips  into  the  liquid  when  the  cover  is  screwed  on.  The  condenser 
is  filled  with  cold  water,  the  burner  lighted,  and  the  heating  continued  until  the  thermometer 
again  shows  a  constant  reading;  the  corresponding  scale-reading  then  gives  directly  the  per- 
centage of  alcohol  by  volume.  In  the  case  of  sweet  wines  or  beers  it  is  advantageous  to  dilute 
with  an  equal  volume  of  water,  the  result  given  by  the  instrument  then  being  doubled. 

An  ingenious  and  simple  capillarimeter,  recently  devised  by  Bosia  and  constructed  by  the 


DENATURANTS 


177 


borne  more  especially  by  alcoholic  beverages.  In  most  countries  alcohol  for  industrial 
purposes  is  almost  free  from  taxation  (see  later),  the  use  of  such  alcohol  for  drinking  being 
prevented  by  addition  of  denaturing  agents. 

Since  1903  the  manufacturing  tax  has  been  reduced  in  Italy  to  12s.  per  hectolitre  of 
100  per  cent,  alcohol  (denatured),  the  ordinary  tax  being  £8  per  hectolitre  (a  bonus  of 
25  per  cent,  or  40  per  cent,  is  allowed  if  made  from  vinasse  or  wine).  Denaturation  was, 
however,  allowed  only  for  alcohol  for  making  ether,  collodion,  mercury  fulminate,  varnishes, 
photographic  papers  or  artificial  silk,  or  for  use  as  fuel  or  illuminant.  In  1905,  the  tax 
of  12^.  was  abolished  for  denatured  alcohol  of  any  origin  (cereals,  vinasse,  etc.),  although 
the  expense  of  denaturant  remains,  this  amounting  sometimes  to  2s.  6d.  or  more  for  about 
3  per  cent,  of  the  general  denaturant  (wood  spirit,  acetone,  pyridine  and  benzene). 

Denaturants  vary  in  different  countries  x  but  are  always  substances  which  are  coloured 

Italian  (Enological  Agency,  Milan,  gives  the  alcoholic  strength  of  wines  or  spirits  with  sufficient 
accuracy  in  three  or  four  minutes. 

The  following  table  indicates  the  volume  of  water  to  be  added  to  100  c.c.  of  alcohol  of  known 
strength  in  order  to  bring  it  to  a  definite  lower  concentration — 


Concen- 
tration 
desired 

GIVEN  ALCOHOL  AT 

95% 
by  vol. 

90  o/o 
by  vol. 

85% 
by  vol. 

80% 
by  vol. 

75% 
by  vol. 

70% 
by  vol. 

65% 
by  vol. 

60% 
by  vol. 

55  % 
by  vol. 

50% 
by  vol. 

90% 

6-4 

85 

13-3 

6-56 

80 

20-9 

13-79 

6-83 

75 

29-5 

21-89 

14-48 

7-20 

70 

39-1 

31-10 

23-14 

15-35 

7-64 

65 

50-2 

41-53 

33-03 

24-66 

16-37 

8-15 

60 

63-0 

53-65 

44-48 

35-44 

26-47 

17-58 

8-76 

55 

78-0 

67-87 

57-90 

48-07 

38-32      28-63 

19-02 

9-47 

50 

95-9 

84-71 

73-90 

73-04 

52-43 

41-73 

31-25 

20-47 

10-35 

45 

117-5 

105-34 

93-30        81-38 

69-54      57-78      48-09 

34-46 

22-90 

11-41 

40 

144-4       130-80 

117-34      104-01 

90-76 

77-58 

64-48 

51-43 

38-46 

25-55 

35 

178-7        163-28 

148-01 

132-88 

107-82 

102-84 

87-93 

70-08 

58-31 

43-58 

30 

224-4 

206-22 

188-57      171-05 

153-53     136-34 

118-94 

101-71 

84-54 

67-45 

25' 

287-0 

266-12 

245-15      224-30 

203-61     182-83     162-21 

141-65 

121-16 

100-73 

20 

381-8 

355-80 

329-84      304-01     278-26    252-58    226-98 

201-43 

175-96 

150-55 

15 

539-5       505-27 

471-00 

436-85     402-81    368-83    334-91 

301-07 

267-29 

233-64 

10 

859-0 
v 

804-50 

753-65 

702-89     652-21    601-60    551-06    500-50 

460-19 

399-85 

c.c.  of  water  to  be  added  to  100  c.c.  of  the  more  concentrated  alcohol. 

For  example,  if  an  alcohol  of  90  per  cent,  by  volume  is  to  be  diluted  to  50  per  cent,  by  volume, 
to  100  c.c.  of  the  former  must  be  added  84-71  c.c.  of  water. 
This  Table  is  calculated  from  the  formula  : 


where  v  is  the  strength  of  the  more  concentrated  alcohol,  S  its  specific  gravity,  8'  and  V  the 
specific  gravity  and  alcoholic  strength  required,  and  x  the  quantity  of  water  to  be  added  to  100  c.c. 


DENATURANTS 

Grade 
wood  spirit 

Crude 
pyridine 

Acetone 

Benzene 

Crude 
benzine 

per  cent. 

per  cent. 

per  cent. 

per  cent. 

per  cent. 

France 

7-5 

— 

2-5 

— 

0-5 

Germany 

1-5 

0-5 

0-5 

— 

— 

,,        (motors) 

0-75 

0-25 

0-25 

2-0 

— 

Austria     . 

3-75 

0-5 

1-25 

— 

— 

,,       (motors) 

0-5 

traces 

traces 

2-5 

— 

Russia 

10-0 

0-5 

5-0 

— 

.  — 

Switzerland 

5-0 

0-32 

2-2 

— 

— 

In  the  United  States  methyl  alcohol  and  pyridine  are  used,  and,  for  special  purposes,  ether, 
cadmium  iodide,  ammonium  iodide,  etc. ;   denaturation  has  been  allowed  only  since  1907. 

In  France  denaturation  costs  about  9  fr.  (7s.)  plus  a  fixed  tax  of  2-2  fr.  per  hectolitre,  and 
VOL.  II.  12 


178  ORGANIC    CHEMISTRY 

or  of  bad  taste  or  smell  and  cannot  be  separated  from  the  alcohol  by  any  of  the  ordinary 
means  (distillation,  etc. ),  but  which  do  not  damage  the  alcohol  for  its  industrial  use.  The 
denaturant  should  vary  according  to  the  use  to  which  the  spirit  is  to  be  put.  There  are 
hence  in  all  countries  a  general  denaturant  (see  preceding  note)  for  alcohol  as  fuel,  for 
motors,  etc.,  and  special  denaturants.  As  colouring-matter,  traces  of  crystal  violet 
(hexamethyl-^-rosaniline  hydrochloride)  are  used  in  Germany.  Alcohol  intended  for  the 
manufacture  of  ether,  collodion,  and  artificial  silk  is  denatured  by  the  addition  of  ether 
and  sometimes  of  a  little  acetone ;  in  Italy,  for  varnishes,  2  per  cent,  of  wood  spirit,  2  per 
cent,  of  light  acetone  oils,  and  20  per  cent.'  of  a  50  per  cent,  solution  of  sealing-wax  are 
used.  It  has  also  been  proposed  to  use  part  of  the  stinking  products  obtained  on  distilling 
certain  bituminous  shales  (see  p.  103). 

The  consumption  of  denatured  spirit  in  different  countries  is  as  follows  (thousands  of 
hectolitres) : 


1905-6 

1908-9 

1909-10 

1910-11 

1911-12 

1912-13 

1913-14 

1914-15 

Italy 
France 

.       36 
.     550 

91 
630 

95 
656 

112 

676 

109 
681 

124 
724 

143 

121 

United  States 

— 

173 

477 

526 

530 

'640 

— 

— 

Austria 

— 

— 

— 

363 

275 

— 

— 

— 

Germany  . 
Norway    . 

.   1400 

1582 

1883 

0-4 

1574 

1720 

— 



The  consumption  of  alcohol  as  a  fuel  for  engines  and  for  illuminating  purposes  is  des- 
tined to  increase  rapidly  in  competition  with  petrol,  which  is  continually  rising  in  price 
(see  p.  86).  In  all  countries,  more  especially  France  and  Germany,  experiments  have 
been  made  on  the  improvement  of  apparatus  for  the  generation  of  light,  motive  power, 
and  heat  by  means  of  alcohol  or  of  suitable  mixtures  of  alcohol  with  petrol  or  benzene. 

Alcohol  engines  are  still  imperfect,  and  would  give  better  results  if  the  pressure  could 
be  increased,  the  distribution  improved,  and  suitable  arrangements  devised  for  super- 
heating and  for  starting.  Existing  petrol  motors  may,  however,  be  worked  with  a  mixture 
of  alcohol,  ether,  and  hydrocarbons  in  such  proportions  that  they  are  mutually  soluble. 

Commercial  benzene  (85  per  cent,  benzene,  14  per  cent,  toluene,  and  1  per  cent,  xylene) 
is  highly  soluble  in  90  per  cent,  alcohol,  and  60  vols.  of  petrol  require  40  vols.  of  95  per 
cent,  alcohol  for  solution.  Hence  95  per  cent,  alcohol  must  be  prepared,  100  vols.  of  it 
dissolving  900  vols.  of  benzene  and  150  vols.  of  petrol.  If  benzene  were  too  dear  (this 
will  not  be  so  for  many  years)  use  could  be  made  of  ether  if  its  price  were  only  7  to  8  per 
cent,  above  that  of  alcohol;  with  ether,  ordinary  lamp  oil  would  remain  dissolved.  A 
good  mixture  for  engines,  distinguished  in  France  by  the  letters  E.H.A.,  contains  65  per 
cent,  of  95  per  cent,  alcohol,  10  per  cent,  of  ether,  and  25  per  cent,  of  hydrocarbons  (benzene 
and  petrol ;  the  latter  facilitates  evaporation  of  the  alcohol  at  a  low  temperature  and  the 
ether  aids  in  the  starting  of  the  cold  engine)  and  has  the  calorific  value  5850  cals.  in 
comparison  with  over  10,000  for  petrol.1 

In  the  United  States,  de  Keghel  has  prepared  a  carburetted  alcohol  by  distilling  60  kilos 
of  93  per  cent,  alcohol  in  presence  of  23  kilos  of  wood-tar  or  masut  and  17  kilos  of  coal, 
with  or  without  addition  of  small  amounts  of  pyridine  materials.  The  alcohol  distilling 
over  carries  with  it  various  hydrocarbons  from  the  tar  or  masut  and  extracts  others  from 
the  coal,  66  kilos  of  carburetted  90  per  cent,  greenish-yellow  alcohol  already  denatured 
being  obtained;  this  is  redistilled  after  neutralisation  with  phosphoric  acid. 

In  1911,  denatured  90  per  cent,  alcohol  cost  46s.  per  quintal  in  Italy,  whilst  in  Germany 
in  1909  it  cost  only  about  half  this,  namely,  25  marks  (shillings)  per  hectolitre  (after  1909, 

the  Government  makes  a  rebate  of  9  fr.  In  Germany  it  costs  only  2  marks  (shillings),  since 
much  less,  although  sufficient,  denaturant  is  added.  In  Italy  denaturation  is  possibly  excessive 
and  too  expensive. 

1  An  automobile  weighing  1200  kilos,  on  a  journey  of  174  kiloms.  (109  miles)  at  30  kiloms. 
(19  miles)  per  hour,  consumed  11-3  litres  of  alcohol;  under  similar  conditions,  10  litres  of  petrol 
are  required.  For  an  8  h.p.  car,  360  grams  of  alcohol  or  500  of  petrol  are  used  per  h.p. 
hour.  For  automobiles  and  explosion  engines  in  general,  the  Paris  Omnibus  Company  uses 
alcohol  mixed  with  50  per  cent,  of  benzene,  this  giving  a  better  thermal  efficiency  (34  per  cent.). 
A  domestic  25-candle  lamp  with  an  Auer  mantle  uses  about  2-36  grams  of  alcohol  per  candle- 
hour.  The  use  of  alcoholene,  a  mixture  of  alcohol  and  ether,  has  now  been  proposed,  and  from 
a  technical  standpoint  presents  advantages  over  alcohol  alone  and  also  over  other  mixtures. 


ALCOHOL    STATISTICS 


179 


with  the  new  tax,  48s.),  in  Austria  26s.,  in  Switzerland  24s.  (retail),  in  Belgium  25s.,  and 
in  France  32s.1 

STATISTICS  AND  FISCAL  REGULATIONS.  The  alcohol  industry  owes  its  great 
development  to  the  enormous  use  made  of  alcohol  in  numerous  manufactures,  and  the 
chemical  industries  of  a  country  in  which  relaxation  of  the  ordinary  fiscal  duty  does  not 
render  this  possible  are  at  a  disadvantage  compared  with  those  of  countries  where  alcohol, 
after  denaturation,  is  procurable  tax-free. 

The  production,  importation,  and  exportation  of  alcohol  in  various  countries  are  as 
follows  (thousands  of  hectolitres,  calculated  anhydrous) : 


1905-6 

1908-9 

1909-10 

1910-11 

1911-12 

1912-13 

1913-14 

1914-15 

Germany        .    prod. 

4,020 

4,263 

3,647 

3,473 

3,451 

3,750 

— 

— 

exp. 

194 

10 

12 

— 

— 

— 

— 

— 

imp. 

— 

— 

— 

— 

— 

— 

— 

— 

Austria-Hun- 

2,700 

2,650 

1,765 

2,086 

1,804 

1,989 

— 

— 

>  exp. 

.1 

. 

...   .. 

-.     . 

..  --. 

—  —  - 

-'••- 

•      '    ' 

gary 

J  imp. 

~~* 

"^ 

*"""' 

~~ 

Russia            .    prod. 

4,500 

— 

— 

— 

— 

5,580 

— 

— 

exp. 

— 

— 

— 

— 

— 

— 

— 

— 

imp. 

— 

—  •  • 

— 

— 

— 

—     - 

— 

— 

United  States   prod. 

2,900 

2,700 

— 

— 

— 

3,650 

— 

— 

exp. 

— 

— 

— 

— 

— 

— 

— 

— 

imp. 

— 

— 

— 

— 

— 

— 

— 

— 

France           .    prod. 

2,700 

2,428 

2,392 

2,182 

2,987 

2,596 

— 

— 

exp. 

— 

— 

— 

— 

— 

— 

— 

— 

imp. 

— 

— 

— 

— 

— 

— 

— 

— 

Great  Britain    prod. 

1,284 

— 

1,500 

— 

— 

.  — 

— 

— 

exp. 

— 

— 

— 

— 

— 

— 

— 

— 

imp. 

— 

15,300 

— 

— 

— 

— 

— 

— 

Holland          .    prod. 

351 

— 

— 

— 

— 

— 

— 

— 

exp. 

— 

— 

— 

— 

-    — 

— 

— 

— 

imp. 

— 

— 

— 

— 

— 

— 

— 

— 

Belgium          .    prod. 

389 

— 

— 

— 

— 

— 

— 

— 

exp. 

— 

— 

— 

— 

— 

— 

— 

— 

imp. 

— 

— 

— 

— 

— 

—  • 

— 

— 

Sweden          .    prod. 

200 

220 

— 

— 

402 

451 

— 

— 

exp. 

— 

— 

— 

— 

— 

— 

— 

— 

imp. 

— 

12 

— 

— 

— 

— 

— 

— 

Norway          .    prod. 

43-7 

— 

— 

11-3 

— 

— 

— 

— 

imp. 

7-3 

— 

— 

30-5 

— 

— 

— 

— 

Italy     .          .    prod. 

293 

800  2 

419 

297 

260 

349 

372 

398 

exp. 

25 

59 

71 

95 

— 

220 

— 

— 

imp. 

— 

— 

— 

— 

— 

— 

— 

— 

Denmark        .    prod. 

154 

— 

— 

155 

— 

— 

— 

— 

exp. 

— 

— 

— 

— 

— 

— 

— 

— 

Switzerland    .    prod. 

— 

— 

— 

54 

57 

53 

— 

— 

imp. 

— 

— 

— 

130 

112 

129 

— 

— 

Turkey            .    prod. 

— 

— 

— 

— 

— 

— 

— 

— 

exp. 

— 

— 

— 

— 

— 

— 

— 

— 

imp. 

— 

175 

— 

— 

— 

— 

— 

— 

Bulgaria         .    prod. 

— 

— 

— 

27 

45 

— 

— 

— 

Whole  world  .    prod. 

— 

21,000 

— 

— 

— 

— 

— 

— 

1  When,  after  the  European  War,  the  State  monopoly  of  alcohol  was  mooted  in  Italy  and 
France,  the  producers  advised  the  respective  Governments  to  lower  the  price  of  power  alcohol 
to  f  1  per  hectolitre  so  as  to  render  advantageous  its  use  on  a  large  scale  for  motive  power,  lighting 
and  heating,  any  loss  being  counterbalanced  by  an  increase  in  the  price  of  potable  alcohol. 

2  This  exceptional  production  corresponds  with  the  famous  cognac  year  (see  Note,  p.  181). 
The  output  was  80,000  hectolitres  in  1878,  165,000  in  1888,  and  187,000  in  1898-1899. 


180 


ORGANIC    CHEMISTRY 


For  every  100  litres  of  alcohol  consumed  as  beverages  the  following  amounts  are  used 
for  industrial  purposes  :  54  litres  in  Germany,  19  in  Austria,  18  in  France,  and  14  in  Great 
Britain.  These  figures  indicate  the  countries  most  addicted  to  alcoholism  (see  p.  184). 
The  importation  and  exportation  of  alcohol  for  Italy  are  as  follows  (hectolitres) : 


1905 

1908 

1910 

1911 

1913 

1915 

1917 

fimp. 
Spirit  in  cask        -{ 
^exp. 

2,508 
19,688 

822 
31,756 

641 

38,604 

647 
2,067 

624 

4,476 

133 
137,715 

9,853 

485 

Cognac,      casks  /imp.  about 
and  bottles      \exp.     _„ 

1,330 
940 

1,460 
300 

1,500 
4,250 

1,200 
1,420 

1,175 
715 

265 
5,600 

690 
170 

Sweetened    and  1  . 
spiced  spirits,   >• 
casks  &  bottles  Jexp> 

3,145 
18,540 

2,940 
38,540 

3,974 
46,815 

2,480 
33,600 

2,420 
25,600 

980 
22,300 

555 
6,690 

The  alcohol  produced  in  Italy  is  obtained  from  the  following  raw  materials  (the  numbers 
represent  hectolitres) :  l 


Cereals 

Molasses 

Beet 

Wine 

Vinasse 

Fruit,  etc. 

Campaign  of  1904-5     . 

90,000 

72,600 



59,000 

83,000 

1,725 

„          „  1908-9     . 

— 

— 

— 

— 

128,883 

— 

„  1910-11    . 

64,934 

154,195 

8,857 

16,436 

46,698 

5,520 

„  1911-12   . 

59,865 

125,538 

9,653 

1,251 

57,848 

6,330 

„  1912-13   . 

112,143 

141,609 

22,942 

2,941 

62,341 

7,155 

„  1913-14   . 

561,390 

175,784 

31,075 

10,281 

88,062 

10,246 

„  1914-15   . 

129,994 

177,496 

13,214 

10,849 

72,622 

10,785 

1  In  1913  there  were  in  Italy  26  large  distilleries  using  starchy  substances,  molasses,  beet 
and  dried  grapes  and  2673  using  fruit,  wine,  vinasse,  honey,  etc.  In  1904-1905  the  spirit  dis- 
tilleries consumed  23,400  tons  of  maize,  600  of  durra,  and  1700  of  barley,  rye,  millet  and  rice; 
also  28,000  tons  of  molasses  and  5300  of  other  materials.  To  these  must  be  added  575,000 
hectolitres  of  wine,  260,000  tons  of  vinasse,  and  1370  tons  of  fruit. 

In  1908-1909,  368,000  tons  of  vinasse  containing  3  to  4  per  cent,  of  cream  of  tartar  and 
about  4  per  cent,  of  alcohol  were  treated ;  the  mean  production  of  vinasse  is  800,000  tons. 

In  Italy  there  are  three  sugar  works  which  also  make  alcohol  (in  1911-1912  about  75,000 
hectolitres  of  molasses)  and  one  factory  at  Cavarzere  (Venetia)  which  obtains  alcohol  directly 
from  the  beet  (4000  hectolitres  in  1911-1912).  In  1911-1912  the  distilleries  of  the  Italian 
Distilling  Company  (at  Milan,  Savona,  Padua,  etc.)  produced  25,000  hectolitres  from  cereals; 
the  Corradini  Distillery  of  Leghorn  produced  10,000  hectolitres  from  cereals  and  the  firm  of 
Schiapparelli  of  Turin,  8000  hectolitres. 

In  the  United  States  spirit  distilleries  consumed  1,270,000  tons  of  maize  and  about  100,000 
tons  of  molasses  (besides  about  5000  tons  of  molasses  for  rum )  in  1912. 

In  1912-1913  there  were  in  the  United  States  398  (in  1911-1912,  417)  grain  distilleries, 
22  (18)  molasses  distilleries,  and  450  (386)  fruit  distilleries,  the  materials  used  being  11,000,000 
(12,000,000)  hectolitres  of  grain  giving  almost  6,000,000  hectolitres  of  whisky,  and  2,300,000 
hectolitres  of  molasses  giving  1,000,000  hectolitres  of  whisky.  Further  130,000  hectolitres  of 
molasses  were  used  to  make  103,000  hectolitres  of  rum,  while  300,000  hectolitres  of  fruit  spirit  are 
also  produced. 

In  Germany  80  per  cent,  of  the  alcohol  comes  from  potatoes  (the  cultivation  of  which  occupies 
3,300,000  hectares  out  of  a  total  cultivated  area  of  26,000,000  hectares).  In  1 911-1912  the  output 
was  3,451,000  hectolitres  of  spirit,  the  materials  used  being  :  1,856,626  tons  of  potatoes  (2,520,000 
tons  in  the  previous  year),  508,737  tons  of  grain,  49,100  tons  of  other  starchy  substances,  82,360 
tons  of  molasses,  193,701  tons  of  beer  residues,  336,000  tons  of  fruit,  324,000  tons  of  wine  and 
vinasse,  and  35,600  tons  of  yeast  and  fermentation  residues. 

In  1912,  150,000  hectolitres  of  alcohol  were  used  in  Germany  to  manufacture  vinegar,  3300  for 
lead  acetate,  36,500  for  celluloid,  5500  for  pegamoid,  32,500  for  esters,  2100  for  photographic 
gelatine,  8350  for  dyestuffs,  225  for  chloroform,  208  for  iocloform,  4200  for  coloured  lacquers  and 
32,000  for  other  lacquers,  2650  for  solid  soaps,  etc.,  and  5641  for  scientific  purposes. 

In  Hungary  1,000,000  hectolitres  of  alcohol  were  consumed  in  1910,  the  distilleries  employing 
4500  workpeople. 

In  Austria  60  per  cent,  of  the  alcohol  made  is  obtained  from  potatoes,  about  one-half  of  the 
Austrian  output  being  furnished  by  Galicia,  where  there  were  900  distilleries  in  1911.  In  1912 
about  29,000  hectolitres  of  alcohol  were  converted  into  vinegar. 

In  France  alcohol  was  protected  by  a  Customs'  duty  of  £2  16s.  per  hectolitre  before  the 


TAXATION    OF    ALCOHOL 


181 


In  Italy  the  tax  for  manufacturing  alcohol  was  21s.  per  hectolitre  at  100  per  cent,  in 
1871,  £4  in  1883,  £6  in  1885,  and  £7  4s.  in  1887;  to  this  the  sale-tax  of  £2  Ss.  was  added 
in  1888  (so  that  the  consumer  paid  about  23  pence  per  litre  in  taxation  alone  ! ) ;  the  sale-tax 
was  abolished  in  1904.  A  rebate  of  90  per  cent,  of  the  tax  is  made  on  exported  alcohol 
(added  to  marsala,  vermouth,  etc. ).  In  1903  alcohol  obtained  by  distilling  wine  and  vinasse 
and  destined  for  industrial  use  was  exempted  of  all  taxation,  and  to  alleviate  the  crisis  in 
the  wine  industry  it  was  proposed,  but  in  vain,  to  grant  a  substantial  bounty  to  the  distillers 
of  wine  and  vinasse.  In  1911  the  tax  was  raised  to  £10  16s.  per  anhydrous  hectolitre  at 
15-56°,  in  1914  to  £13  4s.,  and  in  1919  to  £20. 

In  other  countries  also,  modifications  have  been  made  during  the  past  few  years  in  the 
fiscal  regulations  regarding  alcohol,  for  the  purpose  principally  of  increasing  the  revenue.1 

European  War.  In  1910  the  output  of  2,182,074  hectolitres  of  industrial  alcohol  was  obtained  : 
21-6  per  cent,  from  cereals,  23-5  per  cent,  from  molasses,  and  54-9  per  cent,  directly  from  beet; 
420,000  hectolitres  of  potable  spirit  were  made  from  wine.  In  preceding  years  the  quantities  of 
alcohol  (hectolitres)  obtained  from  different  materials  were  as  follows  : 


From  starchy 
matters 

From 
molasses 

From 
beetroot 

From 
wine 

From 
cider 

Total 

1885. 

567,768 

728,523 

465,451 

23,240 

20,908 

1,864,514 

1897  . 

484,637 

734,819 

798,484 

83,719 

26,579 

2,208,140 

1901  . 

269,074 

1,006,933 

578,628 

330,966 

115,220 

2,437,964 

1904  . 

380,710 

626,722 

992,149 

88,509 

— 

2,181,362 

C            t\  V»     i    4* 

1908  . 

362,500 

448,000 

1,260,000 

468,000 

\    2,600,000 

In  1911  1,073,628  hectolitres  of  alcohol  were  obtained  from  beet  and  in  1912,  owing  to  the 
smaller  beet  crop,  1,014,690;  510,400  hectolitres  were  made  from  molasses  in  1911  and  465,123 
in  1912. 

In  Russia  50  per  cent,  of  the  alcohol  is  derived  from  potatoes,  which  grow  well  under  the  soil 
and  climatic  conditions  prevailing  there;  the  mean  starch  content  of  Russian  potatoes  is  18  per 
cent.,  the  limiting  proportions  being  11  per  cent,  and  22  per  cent. 


1   France 
Germany   . 
Great  Britain 
Austria-Hungary 
Belgium     . 
Italy 
Spain 

Netherlands 
Sweden      .   . 
Norway 
United*  States 
Switzerland 

Russia 


Tax  per 

hectolitre 

£   s. 

8  16 
6   3 

28   8 

3  15 

16  0 

10  16 

2  4 

15  0 

5  16 
13  6 

9  16 
Monopoly 

Monopoly 


Year 

1913 
1912 
1913 
1911 
1912 
1911 
1913 
•1911 
1913 
1913 
1911 
1912 

1911 


In  Italy  the  revenue  from  the  alcohol  tax  has  amounted  to  : 


Bevenue 
£ 

15,978,312 

10,145,612 

18,595,435 

4,477,373 

2,179,677 

1,658,080 

739,757 

3,299,664 

1,288,992 

288,000 

32,182,061 

289,965 

(63,501,812  (net) 
\83,534,099  (gross) 


1906 

£1,556,004 


1907 
1,206,053 


1908 

575,902 


1909 

954,320 


1910 

1,546,768 


1912 
1,917,512 


1914 
1,315,457 


In  Germany  the  manufacturing  tax  of  ordinary  non -denatured  alcohol  varied  prior  to  1909 
from  64s.  to  72s.  per  hectolitre,  this  being  entirely  repaid  on  exported  alcohol,  which  in  certain 
cases  also  enjoyed  a  bounty  of  9s.  Before  1909  the  tax  was  based  on  the  volume  of  the  wort, 
so  that  all  distillers  tried  to  work  with  concentrated  worts  (up  to  25°  Brix).  Nowadays  the 
payment  is  made  on  the  volume  of  anhydrous  alcohol  produced,  and  the  tax  varies  according  to 
the  production,  which  is  established  every  ten  years  for  each  factory  (contingent  production}. 
On  this  contingent  quantity  the  tax  is  105  marks  (shillings)  per  anhydrous  hectolitre,  excess  pro- 
duction paying  125  marks.  There  are  then  supplementary  taxes  of  4  to  14  marks  to  protect  the 
small  factories,  so  that  a  hectolitre  of  alcohol,  costing  of  itself  28s.  to  32s.,  costs,  with  taxes,  £7  4s. 
to  £8  8s.  The  German  Government  received  about  £8,000,000  in  alcohol  taxes  in  1908-1909  and 
expect  in  the  future  to  raise  this  to  £14,000,000.  The  increase  in  the  tax  for  military  expenditure 
was  opposed  by  the  socialists  and  clerical  party  with  abstinence  propaganda,  and  the  consumption 
of  alcohol  fell  in  1909-1910  by  over  600,000  hectolitres.  After  1909  the  tax  amounted  to  about 
37s.  for  ordinary,  and  19s.  for  denatured,  spirit,  and  was  increased  still  further  later;  as  a  result 


182 


ORGANIC    CHEMISTRY 


UTILISATION  OF  DISTILLERY  RESIDUES.  All  the  components  of  the  prime 
materials  used  in  the  production  of  alcohol  are  found  (excepting  the  carbohydrates  :  starch 
and  sugar)  in  the  residues  (grains,  spent  wash)  left  after  the  distillation  of  the  alcohol. 

These  residues  formerly  formed  inconvenient  refuse  (1  ton  of  grain  gives  60  hectolitres 
of  residues),  since  they  readily  undergo  putrefaction  and,  if  discharged  into  rivers  or  canals, 
contaminate  the  water.  In  exceptional  cases,  when  the  distilleries  are  in  large  agricultural 
centres,  the  residues  are  used  in  the  wet  state  for  cattle-food,  but  more  commonly  they  are 
evaporated  and  dried,  these  dried  grains  being  highly  valued  as  a  concentrated  fodder,  rich 
in  proteins  1  and  having  a  restricted  ( 1  :  3  to  1  :  5 )  nutritive  ratio  (ratio  between  nitrogenous 
and  non-nitrogenous  substances).2  In  the  fresh  residues  two-thirds  of  the  part  which  is 
not  water  is  dissolved  and  the  remaining  third  suspended  in  the  water.  Potatoes  give 
about  10  per  cent,  of  dried  residue,  malt  about  40  per  cent.,  and  maize  45  to  50  per  cent. 

It  will  hence  be  understood  how  distilleries  have  greatly  increased  the  raising  of  cattle 
and  consequently  production  of  stable  manure,  thus  contributing  to  the  fertilisation  of 
lands  formerly  unfertile. 

The  economics  of  the  drying  of  these  residues  has  always  constituted  a  difficult  problem 
owing  to  the  presence  of  more  than  90  per  cent,  of  water  in  which  part  of  the  nutritive 
products  is  dissolved  and  to  the  fact  that  the  dried  residues  sell  at  £4  to  £5  10s.  per  ton. 
In  many  cases  the  liquid  portion  is  abandoned  and  the  solid  part  separated  by  filter-presses 
or  centrifuges,  but  if  the  liquid  part  cannot  be  got  rid  of,  even  after  addition  of  lime,  ferrous 
sulphate,  etc.,  it  is  best  to  evaporate  it  by  means  of  the  hot  fumes  from  the  flues,  the  opera- 
tion being  hastened  with  disc-stirrers  of  large  surface  and  with  fans.  The  evaporation 
is  sometimes  carried  out  in  a  vacuum  apparatus  (see  Sugar)  furnished  with  stirrers,  by 
which  means  a  marked  economy  in  fuel  is  effected  (see  also  Vol.  I.,  pp.  563  and  568). 

Of  the  various  drying  systems  (Hatschek,  Meeus,  Porion  and  Mehay,  Venuleth  and 
Ellenberg,  Theisen,  Biittner  and  Meyer,  etc. ),  we  shall  deal  only  with  that  of  Donard  and 
Boulet,  which  has  been  applied  with  advantage  in  France  and  recently  also  in  Italy. 

The  solid  residue  from  the  filters  or  centrifuges  (perhaps  mixed  with  the  evaporated 
residue  of  the  liquid  portion),  still  containing  more  than  50  per  cent,  of  water,  is  carried 
by  mechanical  transporters  into  the  vacuum  drying  apparatus  (Fig.  151),  consisting  of 
a  horizontal  cast-iron  cylinder  rotatable  about  a  hollow  axis  through  which  the  steam 
enters  or  issues ;  its  length  and  diameter  are  2-5  metres.  Inside  are  a  number  of  tubes 
(heating  area  about  60  sq.  metres)  into  which  steam  is  passed  from  D,  the  condensed 
water  being  discharged  without  coming  into  contact  with  the  mass  to  be  dried.  At  the 

the  consumption  of  industrial  spirit,  which  had  ri?en  from  0-32  litre  to  2-3  litres  per  head,  dimin- 
•  ished  in  1912  to  1-3  litres  per  head  per  annum,  while  that  of  spirits  fell  from  6-2  litres  to  3  litres  in 
1912.  Potato  spirit  is  made  in  6400  large  factories,  that  from  cereals  in  730  large  and  6600  small 
factories,  that  from  molasses  in  27  special  distilleries,  and  that  from  wine,  fruit,  and  yeast  in  about 
60,000  small  distilleries.  In  Germany,  besides  the  concession  of  untaxed  denatured  alcohol  to  all 
industries,  non-denatured  alcohol  is  also  allowed  free  of  tax  to  scientific  laboratories  and  for 
medicinal  uses  and  military  explosives.  The  alcohol  of  spirituous  beverages  imported  into 
Germany  pays  a  Customs'  tax  of  about  £14  16s.  per  quintal.  In  Great  Britain  the  spirit  duty 
amounted  to  about  £30,000,000  in  1907. 

In  France  alcohol  for  drinking  pays  a  tax  of  £10  per  hectolitre,  whilst  industrial  spirit  is 
untaxed  (as  in  Germany),  and  is  sold  at  about  4-5  pence  per  litre. 

1  AVERAGE  PERCENTAGE  COMPOSITIONS   OF  THE  PRINCIPAL  RESIDUES 


Beetroot 

Potato 

Rye 

Maize 

Durra 

Barley 

Liquid 

Dried 

Liquid 

Dried 

Liquid 

Dried 

Liquid 

Dried 

Liquid  Dried 

Liquid,  Dried 

Water      . 

91-0 

10-12 

94-0 

8-10 

91-0 

10-12 

90'6 

10-12 

I 
90.3    10-12 

75-0 

14-0 

Proteins  . 

0-9 

6-7 

1-3 

18-24 

1-9 

22-28 

2'0 

24-26 

2-0  ,24-26 

4-0 

20-0 

Non  -  nitrogenous   \ 
matter                  / 

7-2 

60-65 

2-6 

45-55 

5-2 

48-52 

4'9 

35-40 

5-1     30-34 

10-0 

46-0 

Fatty  matter   . 

—       1-3-1-6 

0-2 

3-4 

0-3 

5-6 

1-0 

12-16 

0-7    12-14 

1-7 

7-0 

Cellulose                   I 

0-9      I13'15 

0-9 

9-11 

1-0 

5-7 

ro 

10-12 

1-1     14-16 

5-0 

16-0 

Ash                            / 

t  10-12 

0-5 

1-2 

0-6 

4-6 

0'5 

5-6 

0'8  i    7-8 

1-3 

5-0 

2  For  fodder,  the  nutritive  values  of  the  proteins,  fats,  and  digestible  non -nitrogenous  substances 
are  in  the  proportions  3  :  2  :  1,  so  that  the  commercial  value  of  a  fodder,  expressed  in  nutritive  units, 
is  given  by  :  nitrogenous  substances  X  3  +  fatty  substances  X  2  -f  non -nitrogenous  substances, 
given  by  the  percentage  composition  of  the  digestible  components, 


DISTILLERY    RESIDUES 


183 


other  end,  by  means  of  the  perforated  axis,  Gf,  the  interior  of  the  cylinder  communicates 
with  a  double-action  exhaust  pump  to  carry  away  the  vapour  from  the  grains  which  are 
heated  in  a  vacuum  of  700  mm.,  while  the  cylinder  slowly  rotates  (three  turns  per  minute). 
The  charge  consists  of  2£  to  3  tons  of  solid  grains,  which  are  dried  (to  15  per  cent,  moisture, 
it  then  keeping  well)  in  less  than  four  hours,  the  coal  consumption  being  about  150  kilos. 
By  thus  drying  at  a  relatively  low  temperature  (in  a  vacuum )  and  out  of  contact  with  air, 
the  oil  of  the  grains  does  not  become  rancid. 

Since  maize-grains  contain  as  much  as  15  to  18  per  cent,  of  fat,  it  is  sometimes  con- 
venient to  extract  them  in  one  of  the  forms  of  apparatus  described  in  the  section  on  Fats. 

Special  interest  attaches  to  the  residues  from  Molasses  and  Beet,  since  these  contain 
special  nitrogenous  compounds  (amino-acids)  and  a  large  proportion  of  potassium  salts 
utilisable  for  fertilisers  or  for  chemical  products.  The  evaporation  of  the  liquid  part  of 
these  residues  may  be  carried  to  a  certain  stage  (11°  Be.  in  the  hot  or  14°  in  the  cold)  in  the 
ordinary  vacuum  plant,  the  mass  being  subsequently  completely  evaporated  and  the  residue 
calcined  in  suitable  furnaces  (Porion  model  in  France  and  Belgium)  which  are  similar  to  the 
reverberatory  furnaces  or  muffles  used  in  the  preparation  of  sodium  sulphate  (see  Vol.  I., 
p.  174).  Care  must  be  taken  riot  to  fuse  the  mass,  which,  when  discharged,  should  still  be 


FIG.  151. 

carbonaceous  and,  indeed,  sufficiently  so  to  cause  it  to  burn  when  placed  in  heaps  outside 
the  furnaces ;  the  greyish  or  blackish  mass  thus  obtained  is  known  in  France  as  salin  (see 
Vol.  I.,  p.  545;  process  for  recovering  pure  potassium  carbonate).1 

By  this  treatment,  however,  all  the  nitrogen  compounds  are  lost,  but  in  some  cases  these 
are  used  for  the  extraction  of  methyl  chloride  (see  p.  116). 

During  recent  years  the  utilisation  of  these  nitrogenous  substances  has  assumed  great 
importance  :  according  to  the  Effront  patents  (1907),  the  amino-acids  are  utilised  by 
enzymic  processes  2  for  the  preparation  of  organic  acids  and  ammonium  sulphate  (with 

1  A  sample  from  an  Italian  distillery  showed  the  following  percentage  composition  :  water,  11 ; 
insoluble  matter  (carbon,  sand,  etc.),  10;    KjS04,  9-5;    KC1,  18;    KzC03,  43-7;    Na2C03,  6-5; 
potassium  phosphate,  0-5. 

2  Ehrlich  was  the  first  to  show  that  the  fermentation  of  amino-acids  is  produced  by  amidases. 
Effront  (1908)  found  that  amidases  occur  especially  in  top  beer-yeasts  and  in  aerobic  yeasts 
which,  in  seventy -two  hours  at  40°  are  able  to  transform,  e.  g.,  all  the  nitrogen  of  an  alkaline 
asparagine  (see  this)  solution,  and  almost  all  the  nitrogen  of  the  yeast  itself  into  ammoniacal 
nitrogen,  organic  acids  being  formed  at  the  same  time.     Use  is  made  more  especially  of  butyric 
bacteria  (or  tho?e  often  occurring  in  the  soil),  which  act  in  an  alkaline  medium.     From  1911  to 
1914  the  Effront  process  was  employed  in  the  Nesle  (Somme)  works  with  satisfactory  results. 
The  hot  wash  from  the  spirit  rectifying  column  is  cooled  in  large  vessels  (900  hectolitres)  to  40° 
to  45°,  neutralised  with  lime  or  crude  potash  and  given  an  alkalinity  of  15  to  20  c.c.  of  normal 
caustic  soda  per  litre;    a  little  colophony  (see  note,  p.  167)  is  added   together  with  nutrient 
material  for  the  bacteria,  e.  g.,  50  to  200  grams  of  aluminium  sulphate  and  10  to  50  grams  of 
manganese  and  magnesium  phosphates  and  chlorides  per  hectolitre.     A  pure  5  to  7  per  cent. 


184  ORGANIC    CHEMISTRY 

each  hectolitre  of  alcohol  produced  correspond  25  kilos  of  ammonium  sulphate  and  35  grams 
of  organic  acids,  principally  acetic,  propionic,  and  butyric).  Since  1902,  the  Dessau  Sugar 
Refinery,  and  since  1904  the  Ammonia  Company  of  Hildesheim,  have  utilised  the  nitrogen 
compounds  as  potassium  cyanide  and  ammonium  sulphate.  In  1907  the  Ammonia  Com- 
pany utilised  60  per  cent,  of  the  nitrogen  of  the  residues,  producing  potassium  cyanide 
to  the  value  of  £80,000  and  ammonium  sulphate  to  the  value  of  £20,000. 


ALCOHOLIC   BEVERAGES1 

WINE.  Only  the  liquid  obtained  by  the  spontaneous  alcoholic  fermentation  of  the 
must  of  fresh  grapes,  without  any  addition,  should  be  called  wine.  The  fermentation  is 
spontaneous  owing  to  the  presence  on  the  grapes  of  Saccharomyces  cerevisice. 

culture  of  butyric  acid  bacteria,  already  acclimatised  to  the  concentrated  wash  is  then  introduced 
and  a  current  of  air  passed  through  the  liquid  for  six  to  ten  hours.  Vigorous  action  then  ensues 
with  evolution  of  carbon  dioxide  and  hydrogen,  the  whole  of  the  organic  nitrogen  being  trans- 
formed in  three  days  into  ammonia  and  various  proportions  of  trimethylamine,  acetic  and  pro- 
pionic acids,  considerable  amounts  of  butyric  acid,  glycerol  and  tartaric,  citric  and  succinic  acids, 
etc.,  as  potassium  salts.  The  Nesle  works  obtains  per  hectolitre  of  100  per  cent,  alcohol,  30  kilos  of 
ammonium  and  trimethylamine  sulphates,  30  kilos  of  fatty  acids,'  4  kilos  of  succinic  acid,  2-5 
kilos  of  malic,  citric  and  tartario  acids,  2  to  4  kilos  of  glycerine,  and  30  kilos  of  potassium  sulphate. 
When  this  mixture  is  rendered  distinctly  alkaline  and  distilled,  the  trimethylamine  and  ammonia 
are  evolved,  these  being  passed  over  a  mixture  of  ammonium  and  trimethylamine  sulphates.  In 
this  way  the  gaseous  ammonia  displaces  the  trimethylamine  from  its  sulphate,  forming  ammonium 
sulphate,  the  trimethylamine  liberated  being  either  fixed  by  passing  it  into  water,  or  sent  through 
a  tube  heated  to  1000°  and  thus  transformed  into  hydrocyanic  acid  (from  which  cyanides  are 
made)  and  methane.  The  alkaline  residue  left  in  the  distilling  vessel  is  acidified  with  sulphuric 
acid  and  the  volatile  monobasic  acids  (acetic,  butyric,  etc. ;  the  dibasio  acids  and  the  glycerol  do 
not  distil)  together  with  water  distilled  off;  to  the  distillate  is  added  anhydrous  aluminium 
sulphate  to  absorb  the  water  (which  cannot  be  separated  by  distillation),  the  insoluble  acids  thus 
separated  being  rectified. 

In  the  Nesle  works  600  kilos  of  acetic  acid  and  1000  kilos  of  butyric  acid  were  produced  per 
day  in  1914.  The  glycerine,  dibasic  acids  and  potassium  sulphate  were  recovered  by  evaporating 
the  residue  to  dryness.  These  works  were  closed  in  1914  owing  to  the  nauseous  odours  emitted. 

1  The  average  annual  consumption  per  head  in  litres  of  absolute  alcohol  in  the  form  of  different 
beverages  is  as  follows  : 

Beer  Wine  Spirits  Total 

Germany  .  .4-8  0-66  4-1  9-5 


Austria -Hungary 
France 
Great  Britain 
Belgium   . 
Denmark 
Sweden     . 
Russia 

United  State* 
Italy 


1-7  2-1  5-1  8-9 

1-3  17-5  3-5  22-3 

8-3  0-2  2-3  10-8 

8-7  0-6  3-7  13-0 

2-6  7-0  9-6 

2-3  0-06  3-9  fi-26 

0-2  2-5  2-7 

3-4  0-28  2-7  6-38 

0-1  12-0  2-0  14-1 


In  Sweden  27  litres  of  alcohol  in  the  form  of  spirits  were  consumed  per  inhabitant  in  1830.  In 
Italy  the  consumption  was  6-5  litres  per  head  in  1874  and  10-23  litres  in  1898.  In  Norway  the 
consumption  of  spirits,  which  was  40,000  hectolitres  in  1864,  fell  to  15,000  in  1910,  but  increased 
in  1911. 

The  abuse  of  alcoholic  beverages  is  leading  to  the  ruin  and  decadence  of  certain  nations,  since 
it  is  largely  the  cause  of  depopulation  and  produces  actual  decay  of  the  human  organism.  Alco- 
holism produces  a  diminution  in  stature,  as  is  shown  by  the  increased  numbers  of  those  unfit  for 
military  service ;  it  quickly  leads  to  crime  and  folly,  and  renders  the  organism  easily  attackable 
by  all  kinds  of  disease,  its  effect  being  felt  to  the  third  generation. 

Alcohol  acts  as  a  poison  which  first  excites  and  exalts,  then  intoxicates  and  depresses  the 
psychic  faculty  more  or  less  permanently.  The  abuse  of  wine  and  spirits  is  the  real  cause  of  much 
intestinal  catarrh  and  of  certain  visceral  lesions,  and  sometimes  leads  to  chronic  nephritis,  heart- 
injury,  enlargement  and  inflammation  of  the  liver,  hepatic  cirrhosis,  cerebral  apoplexy,  progressive 
paralysis,  and  often  to  madness. 

Among  the  industrial  classes  it  is  thought  that  alcohol  warms,  prevents  cold,  and  gives  greater 
strength  during  work,  but  this  is  a  great  error  based  on  appearances.  Almost  as  soon  as  it  is 
swallowed,  the  alcohol  of  wine  and  spirits  is  absorbed  by  the  blood  by  means  of  the  capillaries 
and  brought  into  contact  with  all  parts  of  the  organism ;  the  nervous  centres  are  then  more  or 
less  paralysed,  and  the  numerous  capillaries  under  the  skin  dilate,  since  an  increased  amount  of 
blood  rushes  to  the  skin  itself.  The  drinker  has,  indeed,  a  red  face,  but  the  sensation  of  great  heat 
is  only  superficial;  if  the  surroundings  are  cold,  the  heat  of  the  body  is  more  easily  dispersed. 


ALCOHOLISM  185 

In  many  districts  the  fermentation  is  carried  out  on  rational  lines,  selected  yeasts  being 
employed  to  impart  the  taste  and  aroma  of  wines  of  definite  types. 

This  explains  why  drunken  men,  sleeping  on  the  roads  in  the  winter,  quickly  die  of  cold.  Nansen, 
the  famous  Polar  explorer,  withstood  temperatures  52°  below  zero  without  using  alcoholic  liquors. 

The  International  Congress  on  Industrial  Diseases,  held  at  Milan  in  1906,  declared  that  the 
use  of  alcohol  "  is  unnecessary  for  the  nourishment  of  the  workman,  and  becomes  harmful  where 
the  work  is  heavy  or  long.  As  regards  useful  effects  in  the  food  rations  of  the  worker,  alcohol 
may  be  advantageously  replaced  by  sugar,  coffee,  and  tea."  Alcohol  may  diminish  the  using-up 
of  fat  in  the  organism  and  hence  the  consumption  of  proteins,  but  as  a  food  it  is  very  costly  and  of 
little  effect.  Those  accustomed  to  wine  and  beer  may  use  it  in  moderation,  although  these  bever- 
ages are  of  no  advantage  to  the  organism ;  the  use  01  spirits  should  be  abolished  and  it  should  be 
made  a  crime  to  give  spirits  or  even  wine  to  children. 

During  the  last  few  years  alcohol-free  wines  have  been  prepared  by  crushing  grapes  from  the 
best  vineyards  and  subjecting  the  must  to  nitration  and  pasteurisation  (heating  to  60°)  so  as  to 
render  it  clear  and  to  prevent  fermentation ;  the  wine  is  then  stored  in  hermetically  sealed ,  sterilised 
bottles.  These  wines  retain  the  taste  and  fragrance  of  the  grape  and  have  considerable  nutritive 
value,  since  the  sugar  of  the  grape  remains  unchanged  (15  to  20  per  cent.). 

Alcohol  also  has  a  harmful  effect  on  the  reproduction  of  man,  this  explaining  the  slou-ness 
or  the  absence  of  increase  in  population  of  nations  consuming  much  alcohol ;  as  in  France,  where 
£6,000,000  was  spent  in  1898  on  so-called  aperitives  (absinthe,  bitters,  etc.)  alone.  In  Great 
Britain  £60,000,000  is  spent  annually  on  spirits,  and  even  in  Switzerland  £6,000,000.  In  1913 
England  alone  spent  £140,000,000  on  alcoholic  beverages,  Scotland  £16,000,000  and  Ireland 
£14,000,000,  the  average  being  £3  12s.  per  inhabitant;  the  number  of  public-houses  was  141,000 
(1  for  330  persons).  In  the  same  year  there  were  364,400  police-court  cases  of  drunkenness, 
2802  men  and  2074  women  dying  of  alcoholism,  which  also  caused  3605  suicides  and  2488 
attempted  suicides.  Drink  causes  the  direct  or  indirect  death  of  about  45,000  people  annually 
in  France,  40,000  in  Germany,  50,000  in  England,  20,000  in  Belgium,  and  100,000  in  Russia.  In 
Italy,  L.  Ferriani  stated  that  627  cases  of  death  in  1904  were  evidently  due  to  acute  alcoholism. 
Dr.  Ma  ram  bat  affirms  that  in  France  72  per  cent,  of  the  criminals  and  70  per  cent,  of  the  individuals 
(121,688)  appearing  annually  before  the  courts  make  excessive  use  of  alcoholic  liquors.  In  Ger- 
many, A.  Baerfpund  that  41-7  percent.  (13,706)  of  the  prisoners  (32,837)  were  addicted  to  drink; 
in  Switzerland,  it  is  41  per  cent.,  and  in  England,  33  per  cent,  of  those  sentenced  at  the  Assizes. 
In  Holland,  four-fifths  of  the  crime  is  attributed  to  alcohol,  and  in  Sweden  three-fourths.  Similar 
figures  to  the  above  have  been  given  for  Italy.  In  various  countries  it  has  been  found  that 
25  per  cent,  of  the  lunatics  are  excessive  alcohol  drinkers.  In  the  Salpetriere  Hospital  of  Paris, 
60  out  of  83  babies  afflicted  with  epilepsy  had  alcoholic  parents.  In  Germany,  30,000  persons  are 
attacked  every  year  by  alcoholic  delirium  and  other  cerebral  disturbances  due  to  abuse  of  alcohol. 

Alcoholism  in  Germany  was  a  national  calamity  as  early  as  the  fifteenth  and  sixteenth 
centuries,  when  to  the  enormous  consumption  of  beer  was  added  that  of  brandy  and,  later,  of 
cereal  and  potato  spirit.  After  the  eighteenth  century,  when  the  production  of  cereal  and  potato 
spirit  became  a  great  industry,  their  consumption  as  beverages  increased  enormously.  In  1905 
the  annual  expenditure  for  alcoholic  drinks  amounted  to  47.v.  per  head,  or  £8  for  every  person 
over  fifteen  years  old,  making  a  total  of  £120,000,000  for  the  whole  of  Germany,  or  about 
£80,000,000  for  the  working  classes,  corresponding  with  12  per  cent,  of  their  wages.  Every  year 
there  are  200,000  cases  of  inebriety,  and  75  per  cent,  of  the  crimes  against  the  person  are  the  result 
of  drunkenness.  The  question  of  alcoholism  is  closely  connected  with  the  social  problem,  as  it 
is  especially  among  the  working  classes  and  the  ignorant  and  ill-nourished  that  the  victims  are 
found. 

Abstainers  are  less  liable  to  illness  and  usually  live  longer,  as  is  shown  by  the  following  statistics. 
The  Tables  of  the  Sceptre  Life  Association  for  eleven  years  (1884-1894)  show  that  the  mortality 
in  the  temperance  section  (abstainers)  was  57  per  cent.,  and  that  in  the  general  section  (non- 
abstainers  )  81  per  cent.  In  times  of  epidemics  nine  out  of  ten  non -abstainers  die  and  only  two  out 
of  ten  abstainers. 

The  introduction  of  the  alcoholic  tendency  into  Africa,  as  a  result  of  colonisation,  wrought  such 
havoc  among  the  natives  that  the  International  Congresses  against  Alcoholism  held  in  Brussels 
in  1899  and  1906  adopted  various  prohibitive  and  fiscal  measures  to  save  the  black  race  of  Africa 
from  the  terrible  plague.  Many  remedies  for  alcoholism  have  been  proposed,  but  singly  they  are 
almost  all  inefficacious,  though  more  useful  if  combined. 

Increase  of  the  price  of  drink  and  diminution  of  the  number  of  shops  have  proved  almost 
useless  in  France,  Belgium,  and  England.  In  England,  however,  the  latest  increase  in  taxation 
has  diminished  by  one-third  the  consumption  of  spirit;  the  amount  of  beer  drunk  has  fallen  from 
31-4  to  25-8  litres  per  head  per  annum,  whilst  the  consumption  of  tea  and  wine  has  increased. 
In  the  United  States  the  enormous  taxes  on  alcohol  have  not  diminished  the  consumption  of 
liquors.  Sweden  has  obtained  good  results  by  making  a  State  monopoly  of  alcoholic  drinks,  by 
granting  licence  to  sell  only  to  trustworthy  persons,  by  giving  them  special  facilities  for,  and 
large  profits  on,  the  sale  of  other  beverages  and  of  food,  by  abolishing  profit  on  alcoholic  drinks, 
and  by  making  the  licensees  responsible  for  cases  of  drunkenness  on  their  premises.  This  example 
has  been  partially  followed  in  America  and  England,  and  many  temperance  associations  have 
helped  by  opening  establishments  where  good  food  and  drink  are  obtainable  at  low  prices,  alcohol 
being  banned.  In  the  United  States  from  1920  onwards  the  manufacture  of  any  alcoholic  drink, 
including  wine  and  beer,  will  be  prohibited,  so  that  the  grapes  (250,000  tons  per  annum)  of  the 
prolific  Californian  vineyards  will  be  used  to  make  alcohol-free  wine,  syrups,  jams,  etc.  Another 


186  ORGAN  1C    CHEMISTRY 

Grape  must  has  the  sp.  gr.  1-08  to  1-10  and  contains  70  to  86  per  cent,  of  water,  16  to  36 
per  cent,  of  sugar  (glucose  and  levulose,  which  reduce  Fehling's  solution) ;  1  to  3  per  cent,  of 
cream  of  tartar,  tartaric,  malic,  and  tannic  acids ;  0-4  to  1  per  cent,  of  colouring,  aromatic, 
extractive,  gummy,  and  protein  substances,  and  mineral  salts.  If  the  musts  have  to  be 
transported  over  long  distances,  either  they  are  concentrated  in  a  vacuum  or  by  freezing, 
or  the  fermentation  is  interrupted  for  a  time  by  filtering  them.  One  ton  of  grapes  gives 
600  to  700  litres  of  must  and  300  to  350  kilos  of  unpressed  or  160  to  200  of  pressed  residue 
(marc). 

By  fermentation  in  open  vats  the  sugar  is  transformed,  more  or  less  completely,  in 
seven  or  eight  days  into  alcohol,  large  quantities  of  carbon  dioxide  being  developed  and 
a  little  glycerol,  succinic  acid,  etc.,  always  being  formed.  With  more  than  25  per  cent, 
of  sugar,  sweet  wines  are  obtained,  and  with  less,  dry  wines.  Fermentation  cannot  yield 
more  than  15  to  16  per  cent,  of  alcohol,  as  with  more  than  this  proportion  the  yeast  dies. 
After  the  principal  fermentation,  when  the  wine,  without  the  marc,  is  placed  in  casks 
of  chestnut  or  oak,  a  slow  fermentation  goes  on,  this  ceasing  in  the  winter ;  with  increase 
in  the  alcohol-content  and  lowering  of  the  temperature,  the  yeast  and  part  of  the  tartar 
(slightly  soluble  in  alcoholic  liquids )  are  deposited.  In  the  spring,  the  clear  wine  is  decanted 
into  clean  (sulphured  ? )  casks,  which  are  kept  full.  It  may  now  be  placed  on  the  market,  or 
it  may  be  further  matured  by  clarifying  it  in  the  cask  (by  shaking  with  albumin  and  a  little 
tannin  and  allowing  to  stand)  and  by  decanting  and  filtering  it  several  times  during  the 
course  of  a  year  or  more  before  placing  in  well-cleaned  bottles ;  the  latter  are  corked  by 
machinery  with  paraffin-waxed  corks.  As  time  goes  on,  the  wine  acquires  a  pleasing  aroma 
owing  to  esterification  of  small  quantities  of  the  alcohol,  this  process  being  hastened  some- 
times by  pasteurisation,  which  consists  in  passing  the  wine  rapidly  through  coils  heated  to 
about  60°;  this  treatment  also  arrests  certain  incipient  diseases,  which  would  otherwise 
end  by  spoiling  the  wine  (acidity,  etc. ).  Sparkling  wines  are  obtained  by  saturating  the  cold 
wine  with  carbon  dioxide  during  bottling  or  by  bottling  sweet  wines,  the  ^rmentation  of 
which  continues  slowly  in  the  corked  bottle ;  in  the  latter  case,  however,  a  deposit  forms  at 
the  bottom  of  the  bottle. 

In  order  to  obtain  wines  of  constant  type  on  a  large  scale,  co-operative  wineries  have 
been  recently  instituted  in  France,  these  collecting  the  grapes  or  must  from  a  whole  district, 
mixing  it  and  preventing  it  from  fermenting  by  saturating  it  in  the  cold  with  sulphur 
dioxide  (70  grams  liquid  S02  per  hectolitre);  in  this  way,  not  only  the  yeasts,  but  also 
the  moulds,  bacteria,  and  unpleasant  odours  are  destroyed  and  the  must  can  then  be  kept 
for  months  in  closed  vessels.  When  part  of  the  must  is  to  be  converted  into  wine,  it  is 
heated  at  50°  to  60°  in  a  vacuum  by  allowing  it  to  pass  down  a  kind  of  rectifying  column 
(Barbet,  Ger.  Pat.  195,235,  1906),  the  sulphur  dioxide  thus  removed  being  recovered; 
selected  yeast  or  other  wine  rich  in  yeast  is  then  added,  the  resulting  wmes  being  of  uniform 
and  improved  character,  although  somewhat  rich  in  sulphates.  These  desulphurated  musts 
might  well  be  used  as  non-alcoholic  wines.  There  are  also  special  yeasts  capable  of  destroy- 
ing SO2  in  the  musts  and  of  starting  fermentation.  In  Italy  much  was  said  in  favour  of 
co-operation  in  1909  and  1910,  but  no  trial  has  been  made  on  a  large  scale. 

The  proportions  of  the  most  important  components  of  wine  vary  between  wide  limits, 
owing  to  variation  of  the  vines,  soil,  climate,  system  of  wine-making,  and  season  (certain 
wines  contain  manganese,  sometimes  as  much  as  27  mgrms.  per  litre). 

It  is  hence  difficult  to  ascertain  if  there  has  been  an  artificial  addition  of  constituents 
similar  to  those  naturally  present  in  the  wine,  so  that  considerable  dilution  with  water  and 
addition  of  alcohol,  glycerol,  tartar,  sugar,  etc.,  are  not  easy  to  detect  if  they  do  not  exceed 
such  limits.  Natural  wines  may  contain  8  to  16  per  cent,  of  alcohol,  1-6  to  4  per  cent, 
(for  dry  wines,  and  as  much  as  20  per  cent,  or  more  for  sweet  wines)  of  dry  extract  (obtained 
by  evaporating  a  definite  volume  to  dryness  on  a  water-bath  and  drying  in  an  oven  at  100°), 
0-5  to  1-5  per  cent,  of  various  acids  and  tartar  (expressed  as  tartaric  acid)  and  0-15  to  0-45 
per  cent,  of  mineral  substances  (ash,  obtained  by  calcining  the  dry  extract);  the  glycerol 

effective  factor  against  alcoholism  is  education  and  explanation  of  the  evil  effects  of  the  habit : 
in  schools,  churches,  barracks,  the  streets,  workshops,  books,  reviews,  newspapers,  advertisements 
— indeed  everywhere  should  an  intelligent  campaign  be  waged  against  alcoholic  liquor  which,  as 
Gladstone  said  in  the  House  of  Commons,  commits  more  slaughter  in  our  days  than  the  three  historic 
plagues :  famine,  pestilence,  and  war,  since  it  decimates  more  than  famine  and  pestilence  and  kills 
more  than  war,  and  is  in  all  cases  a  disgrace  often  lowering  man  below  the  level  of  the  brute. 


WINE    STANDARDS  187 

varies  from  one-seventh  to  one-fourteenth  part  of  the  alcohol.  Naturally  these  variations 
are  much  smaller  for  wines  of  a  certain  quality  and  year  and  obtained  from  one  and  the  same 
district,  for  which  the  results  of  numerous  analyses  have  been  collected. 

In  Italy  the  following  minimum  legal  limits  have  been  established  as  those  which  must 
be  reached  for  a  wine  to  be  called  natural  (except  in  cases  where  genuine  wines  of  the  same 
origin  and  year  are  shown  to  give  lower  limits) :  alcohol,  8  per  cent,  by  volume  in  white 
wines,  9  per  cent,  in  red;  dry  extract  without  sugar,  1-6  (white),  2-1  (red);  total  acidity 
expressed  as  tartaric  acid,  0-5  (white),  0-6  (red);  ash,  0-15  (white),  0-2  (red);  alkalinity  of 
the  ash  (for  nonplastered  wines)  in  cubic  centimetres  of  normal  alkali  per  litre,  11  (white), 
16  (red);  the  glycerol  should  be  from  one-seventh  to  one-fourteenth  by  weight  of  the 
alcohol,  and  the  relation  between  ash  and  extract  (for  dry  wines  or  for  sweet  wines  after 
deducting  the  sugar)  should  be  about  1  :  10;  plastering,1  expressed  as  sulphuric  acid,  should 
not  exceed  0-2  per  cent. 

In  France  and  now  also  in  Italy,  in  deciding  if  a  wine  is  watered,  use  is  made  of  Gautier's 
rule  (corrected),  according  to  which  the  sum  of  the  percentage  of  alcohol  by  volume  and  the 
total  acidity  (as  sulphuric  acid)  per  litre  should  reach  the  value  12-5  for  red  wines  and  11-5 
for  white  wines. 

Use  is  sometimes  made  of  Halphen's  rule  (1906-1913),  the  results, of  which  are  credited 
by  some  and  discredited  by  others  (Issoglio  and  Possetto,  1914;  Astruc  and  Mahoux,  1908- 
1911;  Prandi,  1914;  Pratolongo,  1917;  Scurti  and  .Rolando,  1917;  Galeazzi,  1916,  etc.). 
According  to  this  rule,  the  ratio  (x)  between  the  fixed  acidity  (expressed  as  sulphuric  acid 
and  increased  by  0-7)  and  the  percentage  of  alcohol  by  volume  (y)  should  differ  by  not  more 
than  0-120  from  the  theoretical  value  calculated  from  the  expression  x  =  1-160  —  0-07  y; 
thus,  for  a  wine  with  10-2  per  cent,  of  alcohol  and  fixed  acidity  3-88,  x  =  (3'88  +  0-7)/10-2  = 
0-449,  while  the  theoretical  value  would  be  1-160  —  (10-2  x  0-07)  =  0-446. 

Wines  weak  in  alcohol  or  tartar  do  not  keep  well  in  the  warm  weather.  A  weak  wine 
may  be  improved  by  either  mixing  with  stronger  wines  or  concentrating  by  freezing,  water 
then  separating  in  the  form  of  ice  (this  method,  in  use  even  in  the  Middle  Ages,  has  recently 
been  patented  in  Italy  ! ). 

New  wine  has  sometimes  the  smell  and  taste  of  rotten  eggs,  i.  e.,  of  hydrogen  sulphide; 
this  may  be  remedied  by  decanting  it  into  casks  in  which  sulphur  has  been  burnt : 
2H2S  +  S02  =  2H20  +  3S.2 

1  In  order  to  prevent  certain  diseases  to  which  southern  wines  low  in  acidity  are  liable,  recourse 
is  had  to  the  addition  of  sulphites,  or  potassium  metabisulphite  (see  Vol.  I.,  p.  544),  which  increase 
the  quantities  of  sulphuric  acid  and  sulphates.     Thus  some  wines  remain  clear  in  the  bottle,  but 
become  turbid  and  dark  on  exposure  to  the  air ;  this  disease,  termed  casse,  is  prevented  by  addition 
of  potassium  metabisulphite,  which  also  arrests  secondary  fermentation.     To  make  certain  weak 
wines  keep  better  in  summer  in  tapped  casks,  calcium  sulphite  is  added,  this  giving  a  slow  evolu- 
tion of  sulphur  dioxide. 

The  keeping  qualities  of  certain  wines  are  improved  by  'plastering,  which  consists  in  adding  to 
the  fermenting  must  a  certain  quantity  of  gypsum  (calcium  sulphate),  but  the  total  sulphates  are 
restricted  by  law  to  2  grams  per  litre  (calculated  as  normal  potassium  sulphate),  excessive  pro- 
portions of  sulphates  being  considered  injurious  to  health.  It  was  formerly  thought  that  the 
gypsum  with  the  cream  of  tartar  would  give  rise  to  insoluble  calcium  bitartrate  and  acid  potassium 
tartrate,  but  instead  of  the  latter  normal  potassium  sulphate  is  the  more  probably  formed  : 
2C4H5OeK  +  CaS04  =  C4H406Ca  +  C4H606  +  K2S04  (Magnanini  and  Ventura,  1902;  Bussy 
and  Buignet,  1865;  Pollacci,  1878;  Roos  and  Thomas,  1896;  Manzato,  1896  and,  especially, 
Borntrager,  1917  and  1918).  Incipient  sourness  of  wine  may  be  corrected  by  adding  normal 
potassium  tartrate  or,  better,  potassium  carbonate  in  amount  calculated  on  the  quantity  of  volatile 
acids  (acetic,  etc.)  present,  and  subsequently  clarifying. 

2  To  desulphur  musts  and  wines  use  is  sometimes  made  of  a  small  quantity  of  urotropine 
(hexameihylenetetramine),  which  decomposes  into  ammonia  and  formaldehyde,  the  latter  fixing 
the  sulphur  dioxide;    such  addition  may  be  detected,  according  to  Fonzes-Diacon  and  Bonis 
(1910),  by  distilling  25  c.c.  of  the  \vine  with  3  drops  of  sulphuric  acid,  acidifying  the  first  5  c.c. 
of  distillate  with  1  c.c.  of  sulphuric  acid,  and  observing  if  it  colours  a  solution  of  ruchsine  decolorised 
with  sulphur  dioxide.     The  residue  from  the  distillation  is  rendered  alkaline  with  magnesium 
hydroxide  and  distilled,  the  vapours  distilling  over  being  condensed  in  a  known   volume  of 
N/10  sulphuric  acid,  which  is  titrated  back  to  ascertain  how  much  ammonia  distils  over  from  the 
urotropine. 

Even  in  a  dilution  of  1  :  50,000,  urotropine  may  be  detected  by  addition  of  mercuric  chloride, 
which  forms  a  precipitate  in  the  shape  of  many-rayed  stars.  With  white  wine  the  reaction  is 
obtained  directly  after  addition  of  a  little  hydrochloric  acid;  red  wine  is  shaken  first  with  solid 
lead  acetate  and  then  with  sodium  phosphate,  and  filtered,  the  filtrate  being  tested  with  HgCl2. 
Milk  is  acidified  with  HC1,  shaken  with  solid  ammonium  sulphate,  filtered  and,  if  turbid,  shaken 
with  petroleum  ether,  the  reaction  being  then  applied  (Rosenthaler,  1913). 


188 


ORGANIC    CHEMISTRY 


From  the  vinasse  remaining  after  the  wine  is  drawn  off  a  little  rather  rougher  wine 
may  still  be  obtained  by  subjecting  it  to  considerable  pressure,  and  from  the  pressed  vinasse 
alcohol  (see  above)  and  tartar  (see  later)  may  be  extracted. 

The  testing  or  analysis  of  wine  is  usually  limited  to  determining  the  alcohol  (by  the 
method  described  on  p.  174),  dry  extract,  ash  (see  above),  glycerol,  plastering,  and  total 
acidity,  and  to  testing  for  the  addition  of  colouring-matter  and  other  adulterations.  The 
complete  analysis  of  wine  is  described  in  Villa vecchia's  "Applied  Analytical  Chemistry," 
Vol.  II.,  pp.  175  et  seq. 

Statistics.  The  countries  which  produce  the  most  wine  are  France,  Italy,  and  Spain. 
For  Italy  the  statistics  are  very  contradictory,  and  even  the  official  ones  are  erroneous ; 
for  instance,  the  production  for  1909,  which  was  given  officially  as  40,000,000  hectolitres, 
was  officially  corrected  in  1910  to  60,000,000  hectolitres.  In  various  countries  the  output 
has  been  greatly  diminished  owing  to  invasion  by  phylloxera.1 

The  average  annual  output  of  grapes  in  Italy  in  1909-1916  was  6,400,000  tons ;  in  1912, 
67,000,000  and  in  1913  8,000,000  tons  were  produced. 

Italy  imports  on  an  average  900,000  bottles  of  fine  wines,  of  the  value  £100,000,  per 
annum.2 

In  Milan  in  1909  duty  was  paid  on  1,000,000  hectolitres,  the  Corporation  receiving 
£420,000,  and  the  consumption  per  head  being  200  litres. 

In  1905  Italy  exported  to  Germany  124,000  quintals  of  dessert  grapes,  whilst  France 
exported  only  78,000  quintals.  In  1892  Italy  exported  about  260,000  hectolitres  of  wine 
to  Germany,  but  less  amounts  in  subsequent  years.3 

1  Phylloxera  (P.  vastatrix  and  P.  viti folia)  is  an  insect  allied  to  the  aphides  and  about  1  mm. 
long.     It  lives  on  the  roots,  leaves  and  tendrils  of  the  vine,  and  quickly  kills  the  latter,  the  roots 
blackening  and  decomposing.     It  was  introduced  into  Europe  on  vines  imported  from  America. 
The  French  vineyards  were  devastated  by  it  in  the  period  1876-1889  (see  above  :  "  Statistics  "). 
the  ordinary  remedies  (flooding,  carbon  disulphide,  potassium  trithiocarbonate,  etc.;  see  Vol.  I., 
pp.  495,  547)  being  without  avail,  owing  to  the  violence  of  the  attack.     Almost  all  the  French 
vines  had  to  be  destroyed  and  replaced  by  American  phylloxera-resisting  vines  on  which  were 
grafted  the  French  vines,  these  giving  grapes  of  the  original  qualities.     Hungary  was  also  hit 
hard  by  phylloxera,  the  output  of  wine  falling  from  7,000,000  hectolitres  in  1880  to  2,000,000  in 
1902.     In  Italv  phylloxera  has  spread  alarmingly,  the  vineyard  areas  attacked  being  :    2458 
hectares  in  1879;   75,612  in  1889;  351,033  in  1899;  410,260  in  1909,  and  605,305 in  1911. 

2  The  output  of  wine  in  other  countries  is  as  follows  (thousands  of  hectolitres)  : 


1902 

1907 

1908 

1909 

1910 

1911 

1912 

1913 

1914          1915 

Germany   . 

2,000 

2,4^2 

3,135       2,020 

846 

2,922 

2,019 

1,005 

921     2,698 

Austria 

5,200 

4,250 

8,142       6,252 

2,546 

3,836 

3,970 

4,352 

3,615        — 

Hungary    . 

2,000 

3,792     8,023 

4,364 

2,764 

4,939 

— 

.  — 

— 

— 

Bulgaria    . 

2,300 

866 

1,643 

1,318 

770 

551 

715 

— 

— 

— 

Spain 

16,000  118,384 

18,557 

14,716 

11,283 

14,747 

16,465 

17,105   16,168 

8,789 

Greece 

1,000 

— 

— 

— 

•  — 

3,230 

— 

— 

3,182 

3,042 

Portugal    . 

5,000 

— 

6,869 

— 

— 

4,074 

— 

— 

.  — 

4,910 

Roumania  . 

2,700 

967 

2,283 

1,270 

1,713 

993 

1,589 

1,158 

660 

1,670 

Russia 

2,300 

— 

.  — 

— 

2,310 

— 

2,600 

— 

— 

— 

Serbia 

500 

536 

856 

394 

153 

— 

— 

— 

— 

— 

Switzerland 

.  — 

681 

925 

408 

408 

854 

903 

264 

507 

870 

Corsica 

— 

— 

254 

194-4 

193-4 

159 

147 

.  — 

.125 

42 

Algeria 

— 

7,853 

7,803 

8,228 

8,414 

8,833 

— 

.  — 

'  — 

— 

Tunisia 

—  - 

357 

345 

350 

250 

440 

290 

300 

200 

125 

Turkey  &  Cyprus* 

2,000 

•  — 

— 

— 

— 

— 

1,800 

— 

— 

— 

Argentine  . 

1,500 

2,843 

3,350 

3,900 

3,817 

4,085 

5,000 

5,144 

4,823 

4,515 

Chile 

2,500 

1,893 

2,260 

2,227 

1,331 

1,904 

2,262 

2,943 

3,080 

1,614 

Uruguay 

— 

185 

162 

170 

147 

105 

194 

165 

165         114 

Australia   . 

327 

202 

250 

209 

266 

226 

277 

214 



— 

United  States     . 

1,100 

— 

.  — 

1,166 

— 

— 

— 

— 

— 

— 

(tons  of 

grapes) 

Whole  World      . 

126,000  142,000 

161,560 

157,500 

89,850 

127,500  144,000 

138,000  146,000  105,500 

3  The  import  duties  levied  by  different  countries  on  Italian  wines  before  the  war  were  as 
follows:  Germany,  29s.  per  quintal;  Belgium  18s.  Qd.;  Holland  34s.;  Great  Britain  23s.  for 
wines  with  less  than  14-84  per  cent,  of  alcohol,  and  54s.  Qd.  for  stronger  ones;  Russia,  45s.; 
United  States,  54«.  6df. ;  and  British  India,  33s.  Qd. 


PRODUCTION    OF    WINE 

The  following  figures  represent  hectrolitres  (1  hectolitre  =  22  gallons) : 


189 


France 

Italy 

Production 

Production 

Exportation  * 

1875 

83,000,000 

28,000,000 

363,000 

1879 

25,000,000 

34,000,000 

1,075,000 

(phylloxera) 

1887 

24,333,000 

34,000,000 

3,603,000  (2,800,000  to  France) 

1889 

23,000,000 

22,000,000 

1,440,000  (commercial  treaty  with  France  broken 

in  1887) 

1893 

59,000,000 

32,000,000 

2,362,000  (750,000  to  Austria-Hungary  ;    300,000 

to    Switzerland,2    and   426,000  to 

America) 

1897 

32,000,000 

28,000,000 

2,400,000 

1901 

58,000,000 

44,000,000 

1,334,000 

1902 

— 

35,000,000 

2,164,000  (976,300  to  Austria-Hungary) 

1904 

— 

42,000,000 

1,200,000  (Austro-Hungarian    market     lost    by 

new  commercial  treaty) 

1905 

57,000,000 

28,000,000 

980,000  (worth  £1,400,000) 

1908 

66,500,000 

52,000,000 

1,200,000 

1909        66,000,000 

60,000,000 

1,450,000  (France  has  a  vine  area  of  1,625,630 

and  Italy  of  3,500,000  hectares) 

1910        28,723,000 

29,293,000 

1,812,000  (£2,400,000) 

1911        53,879,156 

42,655,000 

960,722    (plus  bottled  wine  to  the   value   of 

(of  which 
8,900,000  in   Al- 

£400,000) 

:  geria  and  160,000 

in  Corsica) 

1912        63,831,000 

44,123,000 

863,970  (£1,440,000) 

1913        52,000,000 

52,240,000 

1,466,600   (£2,440,000,  plus  bottled  wine  worth 

(wjth  Algeria) 

£520,000) 

1914        70,134,160 

43,000,000 

1,785,500 

(with  Algeria) 

1915        25,000,800 

19,000,000 

742,000 

(European  war) 

1916        44,800,000 

39,000,000 

398,000  (£1,280,000) 

(of  which 

8,800,000  in  Al- 

geria) 

1917 

42,000,000 

48,000,000 

1,024,000  (£3,840,000) 

(with  Algeria) 

1918 

— 

36,408,000 

2,560,000  (£9,600,000,  plus   bottled  wine  worth 

£560,000) 

1919 

— 

30,000,000 

The  wine  (hectolitres)  exported  from  Italy  to  different  countries  is  as  follows  : 


1909                  1910                  1911 
France      ....        43,725         73,560         45,446 
Germany            .          .          .       193,960         93,868         85.130 
Switzerland       .         .          .      922,950       637,300       332,415 
Egypt       ....        32,000         23,420           9,620 
Argentine           .         .          .      211,620       241,900        165,977 
Brazil       ....       129,589        156,226        136,980 
United  States    .          .          .       138,180        126,522         70,200 
Other  countries           .          .       124,613        140,887        111,760 

2  The  following  is  a  statistical  resume  of  the  wine  imported  into 

From                    1906                      1908                      1910                      1912 
Italy    .         .       137,843           531,776           828,559      -    200,000 
France          .      273,731           363,769           216,909 
Spain  .          .       123,587           415,052           422,775 
Austria         .        53,411             69,634           110,608 
Greece          .          9,370             12,209            64,874 

1912 
23,679 
19,022 
200,565 
7,000 
153,720 
176,695 
73,320 
84,200 

Switzerland 

1913 
570,000 

1913 
235,578 
46,640 
569,465 
8,300 
148,954 
186,485 
99,224 
117,985 

(hectolitres) 

1914 
693,000 

190 

Among  the  many  taxes  imposed  by  Italy  to  settle  the  enormous  war  debts  was  one  (dated 
September  30,  1919)  of  9*.  6d.  per  hectolitre  on  wine  produced  and  on  that  remaining  from 
1918. 

MARSALA.  This  is  a  liqueur  wine  made  for  the  first  time  at  Trapani  in  1773  by 
J.  Woadhouse  of  Liverpool  to  compete  with  the  world-famous  Madeira.  In  1812  another 
large  establishment  was  started  by  the  Englishman,  Benjamin  Ingham,  and  in  1840 
Vincenzo  Florio's  factory,  which  has  since  become  the  most  celebrated.  The  prime  material 
for  the  manufacture  of  Marsala  is  white  Trapani  wine  with  13  per  cent,  of  alcohol,  to  which 
is  added  (in  quantity  varying  for  different  types  of  Marsala)  the  must  (cotto)  of  very  mature 
white  grapes,  concentrated  in  open  boilers  until  two-thirds  has  evaporated ;  then  is  added, 
in  varying  amount,  sifone,  obtained  by  filling  a  cask  to  the  extent  of  three-fourths  with 
clear  must  from  a  very  ripe  white  grape,  and  one-fourth  with  pure  alcohol  (free  from  tax 
if  for  export),  mixing  and  allowing  to  age  so  as  to  develop  the  Marsala  aroma. 

Mixtures  of  these  three  components  in  different  proportions  give  the  various  brands 
of  Marsala  :  the  Italian  brand  is  the  least  alcoholic  (16  to  17  per  cent.),  the  original  English 
brand  the  strongest  (up  to  24  per  cent,  of  alcohol),  while  the  Margherita  and  Garibaldi 
brands  are  of  intermediate  strengths  and  are  sweeter. 

In  1905  Italy  exported  in  cask  29,765  hectolitres  of  Marsala,  worth  £83,280,  and  51,000 
bottles,  value  £2040;  in  1908,  24,900  hectolitres;  in  1910,  32,500;  in  1912,  30,381  and  in 
1913,  28,695  hectolitres  (£103,302)  in  cask  and  3000  (£19,200)  in  bottle. 

VERMOUTH.  This  was  prepared  formerly  in  Tuscany,  but  nowadays  almost  exclu- 
sively in  Piedmont,  where  the  industry  was  started  in  1835  by  Giuseppe  Cora  and  A. 
Marendazzo. 

The  prime  material  for  manufacturing  vermouth  is  the  muscat  wine  of  Asti  and  of 
the  Monferrato  heights,  which  contains  6  to  1 1  per  cent,  of  alcohol  and  2  to  4  per  cent,  of 
sugar;  with  this  is  mixed  2  to  5  per  cent,  of  a  vinous  infusion  of  aromatic  drugs, in  which 
worm  wood  predominates,  and  which  contains  also  sweet  flag,  juniper,  gentian,  etc. ;  finally 
alcohol  is  added  to  bring  the  strength  up  to  15  to  18  per  cent,  and  sugar  to  the  density  of 
5°  to  9°  Be.  (if  for  exportation,  90  per  cent,  of  the  alcohol  and  sugar  taxes  are  refunded). 
Sparkling  vermouth  is  made  by  saturating  it  with  CO2  in  the  cold  under  pressure. 

It  cannot  be  said  that  in  the  manufacture  of  Marsala  and  vermouth  all  the  rational 
methods  prescribed  by  modern  cenotechnics  are  followed.1 

The  production  of  vermouth  in  Piedmont  is  now  about  300,000  hectolitres,  the  exports 
(especially  to  America)  being  8960  hectolitres  in  cask  and  64,980  in  bottle  in  1906;  7874 
in  cask  and  83,300  in  bottle  in  1908;  10,176  (£27,680)  in  cask  and  100,000  (£464,920)  in 
bottle  in  1909;  20,400  (£53,040)  in  cask  and  173,760  (£760,000)  in  bottle  in  1910; 
25,000  in  cask  and  94,000  in  bottle  in  1911 ;  32,000  in  cask  and  131,500  in  bottle  in  1912, 
and  34,300  (£119,360)  in  cask  and  133,600  (£720,000)  in  bottle  in  1913. 

CIDER.  This  is  an  alcoholic  drink  obtained  by  the  partial  fermentation  of  the  juice 
of  apples  and  pears  (perry).  It  is  largely  used  in  the  north  of  France,  in  Germany,  and  in 
Switzerland.  It  is  consumed  almost  immediately  it  is  made.  In  France  the  production 
varies  from  8,000,000  to  30,000,000  hectolitres,  part  of  which  is  distilled  to  produce  alcohol 
(30,000  to  70,000  hectolitres  of  alcohol). 

LIQUEURS.  These  contain  40  to  70  per  cent,  of  alcohol.  The  finest  are  those  obtained 
by  collecting  the  first,  more  highly  alcoholic  distillate  from  other  fermented  liquors.  Such 
are  brandy  (prepared  by  distilling  vinasse  or  wine  and  containing  45  to  55  per  cent,  of 
alcohol),  cognac,  kirschwasser  (obtained  especially  from  the  cherries  of  the  Black  Forest), 
rum  (prepared  principally  in  Jamaica  by  distilling  fermented  cane-sugar  molasses),  mara- 
schino (prepared  from  small  Zara  cherries), -gin  (from  juniper  berries),  atole  or  chica  of 
South  America,  arrack  of  the  Arabs  and  Indians  (prepared  from  rice,  cane-sugar,  and 
coconuts),  schnapps  of  the  Germans  (potato  spirit),  etc. 

The  other  class  of  liqueurs  comprises  those  obtained  from  aromatic  substances,  sugar, 
and  more  or  less  concentrated  pure  alcohol.  In  this  way  are  obtained  rosoli,  anisette, 
absinthe  (alcoholic  decoction  and  distillation  with  wormwood) — much  used  in  France 
and  the  principal  cause  of  the  terrible  effects  of  alcoholism  (p.  184) — creme  de  menthe,  creme 
de  cafe,  etc. ;  ratafia  from  fruit  must,  spirit,  and  sugar ;  Chartreuse  (the  most  celebrated 

1  In  Italy  and  also  in  other  countries  vermouth  may  not  be  coloured  with  aniline  dyes,  but 
the  Municipal  Hygiene  Authority  of  Milan  limits  such  prohibition  to  vermouth  wine,  colouring 
being  allowed  if  the  product  is  declared  simply  as  vermouth  (as  with  liqueurs). 


KEFIR  191 

was  that  prepared  by  the  Carthusian  monks,  before  their  expulsion  from  France  in  1904, 
from  balm-mint,  cinnamon,  saffron,  hyssop,  angelica,  sugar,  alcohol,  and  other  ingredients), 
coca  (from  Bologna),  curacao  (first  prepared  from  two  kinds  of  orange  in  the  island  of  Curasao 
in  the  Antilles),  kummel  (in  Russia  the  best  kinds  are  obtained  by  distilling  brandy  or 
alcoholic  liquids  with  Dutch  cumin  seeds  and  dissolving  pure  sugar  in  the  highly  alcoholic 
distillate).  It  is  unnecessary  to  mention  that  all  liqueurs,  even  the  most  celebrated,  are 
more  or  less  poorly  imitated  in  all  countries  with  mixtures  in  no  way  resembling  the  original 
types,  but  the  latter  always  command  very  high  prices. 

Cognac  is  a  brandy  prepared  especially  in  Charente  by  very  carefully  distilling  weak 
wines  of  special  vintages  and  refining  and  maturing  the  product  in  casks  of  Angouleme 
or  Limousin  oak,  which  gradually  imparts  to  the  spirit  a  pale  yellow  colour  and  a  character- 
istic aroma.  The  finer  and  older  brands  sell  at  as  much  as  £40  per  hectolitre  (see  note, 
p.  180). 

FERMENTED  MILK.  This  bears  the  following  names  according  to  the  locality 
and  method  of  its  preparation  and  the  nature  of  the  milk  from  which  it  is  made  :  kephir, 
koumis,  galazin,  leben  (Egypt),  and  mazun.  The  first  three  of  these  are  the  best  known. 

KEPHIR,  or  Kefir,  is  of  very  ancient  origin  among  the  Caucasian  highlanders,  who 
nowadays  make  enormous  use  of  it  and  jealously  keep  the  secret  of  its  preparation.  There 
is  a  legend  to  the  effect  that  Allah  was  the  first  to  make  it,  and  that  he  recommended  it 
as  a  remedy  for  various  diseases.  Kephir  is  simply  cows'  milk  (fresh  or  skim)  fermented 
by  the  addition  of  a  special  ferment  in  the  form  of  granules,  which  the  Russians  call  "fungi  " 
and  the  Tartars  "grain  or  millet  of  the  Prophet,"  as  they  regard  it  as  discovered  by  Mahomet. 
It  was  only  in  1882  that  Dr.  Dmitrieff  called  the  attention  of  the  rest  of  Russia  and  of 
Europe  to  kephir  and  its  great  recuperative  properties  in  cases  of  lung  diseases. 

Kern  and,  later,  Freudenreich  showed  that  the  alcoholic  fermentation  of  milk  with 
millet  of  the  Prophet  is  due  to  the  simultaneous  action  (symbiosis)  of  the  new  Saccharomyces 
kephiri  (similar  to  ordinary  Saccharomyces  ellipsoideus),  a  streptococcus,  and  a  bacillus. 
The  alcoholic  fermentation  of  milk-sugar  with  evolution  of  CO2  takes  place  rapidly  and 
is  always  accompanied  and  followed  by  acid  fermentation  (lactic  acid),  which  partially 
dissolves  the  casein  (propeptones )  and  forms  a  very  fine  coagulation,  almost  a  frothy 
emulsion.  In  practice  the  kephir  granules  (or  about  2  grams  of  kephir-extract  per  litre 
of  milk)  are  softened  with  tepid  water  (30°  to  35°)  for  a  couple  of  hours,  the  milk  being 
then  added  and  the  mixture  shaken  every  hour  for  eight  hours ;  it  is  then  sealed  in  clean 
bottles  fitted  with  mechanical  stoppers  and  is  shaken  now  and  then,  the  temperature 
being  maintained  at  15°  to  20° ;  in  twenty-four  hours'  time  the  kephir  is  ready ;  it  forms  a 
slightly  alcoholic  and  acidulated  dense,  frothing  liquid.  If  the  kephir  is  left  in  closed 
bottles  for  two  days,  the  pressure  increases  and  the  mass  becomes  more  acid  and  more 
liquid ;  by  the  third  day  it  becomes  extremely  acid  and  contains  up  to  about  2  per  cent,  of 
alcohol,  and  after  this  it  is  inadvisable  to  drink  it. 

In  Italy  kephir  or  kephir-extract  is  placed  on  the  market  by  the  Borgosatollo  Dairy 
(Brescia)  and  kephir  dried  in  vacua  is  also  prepared  (Rosemberger,  Ger.  Pat.  198,869, 
1907). 

KOUMIS  is  similar  to  kephir,  and  of  equally  ancient  origin,  but  is  prepared  from  mares' 
milk.  In  Russia  there  are  various  sanatoria  which  make  efficacious  use  of  large  quantities 
of  koumis.  The  composition  of  the  latter  has  been  found  to  be :  Water,  94  per  cent. ; 
CO2,  0-9;  ethyl  alcohol,  1-7;  lactic  acid,  0-7 ;  lactose,  1-3  (before  fermentation  5-5);  fats, 
1-3;  proteins,  2-3  (largely  peptonised);  salts,  0-3. 

GALAZIN  is  obtained  by  placing  skim  (cow's)  milk,  with  2  per  cent,  of  sugar  and 
0-3  per  cent,  of  beer-yeast  in  strong,  tightly  stoppered  bottles,  and  allowing  fermentation 
to  proceed  for  twenty-four  hours  at  16° ;  from  the  second  to  the  sixth  day  the  proportion 
of  alcohol  rises  from  0-3  to  1-5  per  cent.  Galazin  is  less  nutritious  than  kephir  or  koumis. 

BEER 

This  is  another  alcoholic  liquor  saturated  with  CO2  and  is  obtained  by 
fermenting  aqueous  decoctions  of  barley-malt  and  hops. 

The  ancient  Egyptians  were  acquainted  with  the  manufacture  of  beer  and  held  it  in 
great  regard.  Later  it  became  known  to  the  Ethiopians  and  the  Hebrews,  but  the  Greeks 


192 


ORGANIC    CHEMISTRY 


never  acquired  a  taste  for  beer.  The  industry  was  taken  by  the  Armenians  from  Egypt 
into  the  interior  of  Asia,  and  still  later  beer  was  manufactured  in  Spain  and  France,  but 
it  was  never  consumed  by  the  Romans.  In  Germany  beer  has  been  made  from  time 
immemorial. 

A  marked  improvement  in  the  manufacture  of  beer  dates  from  the  time  of  Charles 
the  Great,  when  hops  were  first  used. 

Lager  beer  (see  later)  was  prepared  as  early  as  the  thirteenth  century,  and  its  use  has 
since  greatly  extended  in  various  countries. 

In  England  the  manufacture  has  flourished  since  the  fifteenth  century,  the  famous 
porter  being  first  made  at  the  beginning  of  the  eighteenth  century. 

The  improvement  made  in  brewing  operations  by  the  introduction  of  scientific  methods 
has  led  to  a  very  considerable  development  of  the  industry  in  Germany  and  elsewhere. 

In  all  stages  of  the  manufacture  the  greatest  cleanliness  is  now  practised,  the  walls 
and  floors  as  well  as  the  vessels  being  frequently  disinfected  by  means  of  dilute  calcium 
bisulphite  solution  (1  per  cent.),  or  hydrofluoric  acid  solution,  or  ozone  (see  Vol.  I.,  p.  202). 

1.  A.  BARLEY  x  should  satisfy  the  following  requirements  : 

1  Barley  (botanical  species  Hordeum)  used  for  making  beer  is  of  two  types  :  two-rowed  (Fig. 
152),  in  which  the  corns  are  arranged  in  the  ear  in  two  rows,  one  on  each  side,  and  six-rowed 


FIG.  152. 


FIG.  153. 


(Fig.  153),  in  which  there  are  three  rows  of  corns  on  each  side  of  the  ear.  Barleys  of  different  kinds 
may,  to  some  extent,  be  recognised  by  the  form  of  the  small  bo-tal  bristle  found  at  the  base  of  the 
corn  inside  the  longitudinal  furrow.  The  value  of  barley  for  brewing  purposes  is  largely  influenced 
by  the  nature  of  the  soil,  climate,  methods  of  cultivation,  and  manuring.  Barley  is  cultivated  in 
all  countries  and  in  all  climates — in  Holland  and  also  in  Sicily.  It  is  difficult  to  keep  varieties 
pure,  since  they  become  modified  during  growth  owing  to  crossing.  Only  by  the  rational  system 
of  selection  initiated  by  Dr.  Nilsson  at  the  Svalof  Institute  is  it  possible  to  fix  different  varieties 
with  constant,  well-marked  characters  suited  to  the  various  districts  in  which  at  one  time  they 
originated. 

From  a  commercial  point  of  view,  the  weight  of  a  barley  is  of  importance  and  good  qualities 
give  a  weight  of  40  grams  per  1000  corns,  or  62  to  67  kilos  per  hectolitre  for  thin  barleys  and  as 
much  as  70  kilos  per  hectolitre  for  the  larger  ones.  The  grains  should  have  a  floury  and  not  a 


HOPS 


193 


(a)  When  moistened  and  kept  at  25°  to  30°,  80  per  cent,  of  the  corns  should  germinate 
in  forty-eight  hours  and  90  to  95  per  cent,  in  seventy-two  hours. 

(b)  Those  are  preferred  which  are  heaviest  (60  to  70  kilos  per  hectolitre)  and  contain 
about  62  per  cent,  of  starch,  about  10  per  cent,  of  protein,  and  12  to  14  per  cent,  of  moisture. 

The  richer  the  barley  in  proteins,  the  less  is  the  amount  of  dry  extract  yielded  by  the 
malt;  thus  a  barley  with  11  per  cent,  of  albuminoids  gives  a  malt  yielding  at  most  76  per 
cent,  of  dry  extract,  whilst  one  with  7  per  cent,  of  albuminoids  gives  a  malt  yielding  81  to  82 
per  cent.     Often,  however,  the 
barleys    richer    in    starch    are 
poorer  in  nitrogen. 

(c)  The  skin  should  be  thin 
and  the  colour  pale  yellow,  the 
ends   of   the    corns   not   being 
brown. 

Barley  starch  swells  at  50°, 
and  with  water  forms  a  paste 
at  80°.  With  diastase  it  begins, 
unlike  potato  starch,  to  sac- 
charify as  soon  as  it  is  com- 
pletely transformed  into  paste. 

B.  Wheat  is  sometimes  used, 
together  with  barley,  for  pale 
beers. 

C.  Maize  is  used  in  America 
after    being   skinned   and    de- 
germed,    the   germ   being   rich 
in    oil.     Prepared    maize    and 
rice  are  used  in  Great  Britain. 

D.  Rice  is  used  in  America 
and     Scandinavia     with      the 
barley. 

2.  HOPS.  The  female 
flowers,  dry  and  mature,  of 


FIG.     154. 


Humulus  lupulus  (Fig.  154)  are 

used,  these  containing  10  to  17 

per  cent,  of  a  powder,  lupulin 

which  can  be  separated  by  shaking  and  sieving),  possessing  the   aromatic   and  bitter 

principles  which  bestow  on  the  beer  its  aroma  and  keeping  qualities.1 

vitreous  appearance  when  cut  through,  and  there  should  be  few  broken  corns,  as  these  do  not 
germinate  and  become  mouldy  on  the  malting  floor.  Germination  tests,  made  on  500  or  1000 
corns,  should  show  at  least  95  per  cent,  of  germinated  corns  in  five  to  six  days.  With  barley 
harvested  under  wet  conditions,  the  ends  of  the  corns  are  darkened. 

The  world's  -production  of  barley  in  1906  was  31,500,000  tons,  in  1910  31,000,000  tons,  and  in 
1913  36,600,000  tons.  In  1910  (and  also  in  1913)  France  produced  1,080,000  tons  (17,000,000 
hectolitres  from  an  area  of  737,300  hectares).  In  1913  Germany  produced  3,673,200  tons, 
Austria  1,750,000,  Hungary  1,730,000,  Bulgaria  300,000,  Denmark  600,000,  Spain  1,500,000, 
Great  Britain  1,500,000,  Roumania  600,000,  Russia  12,100,000,  United  States  3,900,000,  Canada 
1,050,000,  Japan  2.370,000  and  Algeria  1,090,000.  Italy  produces  on  the  average  220,000  tons 
of  barley  per  annum  and  imported  the  following  quantities  of  malt  (mainly  from  Austria  and 
Germany)  : 

1908  1910  1912  1913  1914  1916 

Tons   .          .       12,400  17,800  19,108  15,843  18,200  8,890 

£         .         .      89,240         128,080         244,582         202,790         276,800         157,000 

1  In  regions  where  hops  are  cultivated  on  an  industrial  scale,  the  agriculturists  whose  lands 
border  on  the  hop  gardens  are  compelled  by  law  to  destroy  any  male  hop  plants  accidentally 
growing  in  their  fields.  The  non -fertilised  female  flowers  do  not  bear  fruit. 

The  best  hops  are  cultivated  in  Bohemia  (at  Saaz),  Bavaria,  Posen,  Wiirtemberg,  Baden, 
and  Alsace-Lorraine,  where  they  are  picked  towards  the  end  of  August.  If  they  are  too  ripe  the 
bracts  of  the  hop-cones  open  and  lupulin  is  lost.  The  most  extensive  cultivation  of  hops  takes 
place  in  the  United  States. 

The  hop  should  have  a  bright  yellowish  green,  and  not  a  brown,  colour,  and  the  bracts  should 
not  be  open ;  a  too  green  colour  indicates  that  the  hops  have  been  picked  in  an  unripe  condition. 
VOL.  II.  13 


194 


ORGANIC    CHEMISTRY 


3.  WATER.  Formerly  water  for  brewing  purposes  was  invested  with  a  mysterious 
importance,  but  nowadays  the  water  is  tested  in  a  much  more  rational  and  rigorous 
manner.  Preference  used  to  be  given  to  moderately  soft  water,  but  now  waters  of 
medium  hardness  are  regarded  as  best,  as  it  is  found  that  a  certain  quantity  of  calcium 
sulphate  aids  fermentation,  but  if  the  water  is  too  hard,  less  extract  is  obtained  from  the 

The  seeds  have  no  value  for  brewing  purposes,  the  largest  hops  being  of  least  value.  They  should 
not  have  an  unpleasant  odour.  Since  the  fresh  hops  contain  75  to  85  per  cent,  of  moisture,  so 
that  they  will  not  keep,  it  is  necessary  to  dry  them  in  the  air  or  in  ovens  at  25°  to  30°  in  a  strong 
current  of  dry  air,  until  they  contain  only  12  to  15  per  cent,  of  moisture ;  they  will  then  keep  well, 
even  for  a  year  or  more.  Their  keeping  qualities  may  be  improved  by  sulphuring  them  (with  S02 ) 
either  when  dry  or  during  the  drying.  Sulphuring  is,  however,  often  applied  to  inferior  hops  to 
mask  their  defects. 

The  better  qualities  are  seldom  sulphured  and,  when  they  are  well  dried,  are  kept  tightly 
compressed  in  large  sacks  or  in  evacuated  metal  cylinders.  They  may  also  be  kept  in  a  very  cool 
place  (cold  store). 

The  bitter  flavour  and  keeping  properties  imparted  by  the  lupulin  of  hops  depend  mainly 
on  their  content  of  humuUne,  which  is  a  sesquiterpene,  C15H21,  and  on  that  of  the  a-  and  fi-bitter 
aciclf,  which  varies  from  6  to  18  per  cent.  The  o-acid  is  humulene,  C20H3205,  and  the  £-acid, 
lupitlinic  acid,  C25H36O4 ;  both  are  insoluble  in  water  and  very  bitter,  and  may  be  determined  by 
Lintner's  method  as  follows  :  10  grams  of  an  average  sample  of  the  hops  are  heated  in  a  flask 
graduated  at  505  c.c.,  with  350  c.c.  of  light  petroleum  (b.-pt.  30°  to  50°)  for  six  hours  on  a  water- 
bath  at  40°  to  45°,  an  efficient  reflux  condenser  being  fitted  to  the  flask.  When  the  latter  is  cold, 
it  is  filled  to  the  mark  with  light  petroleum  and  shaken,  the  contents  then  being  filtered.  100  c.c. 
of  the  filtrate,  mixed  with  80  c.c.  of  alcohol,  is  titrated  with  decinorma"!  potassium  hydroxide 
solution  in  presence  of  10  to  15  drops  of  phenolphthalein  solution.  If  much  fat  is  present  an 
aliquot  part  of  the  light  petroleum  solution  is  evaporated  and  the  residue  extracted  with  methyl 
alcohol,  which  does  not  dissolve  the  fat  and,  on  evaporation,  gives  the  bitter  acids ;  these  may 
then  be  weighed. 

The  quality  and  commercial  value  of  hops  are  influenced  largely  by  the  nature  of  the  soil  and 
the  quality  of  the  manure  used,  as  well  as  by  the  variety  of  the  hop  itself. 

Chemical  composition  does  not  always  give  satisfactory  indications  for  judging  of  the  value 
of  hops,  and  this  is  almost  always  done  by  men  experienced  in  valuing  hops.  Hops  eive  up 
to  alcohol  22  to  30  per  cent,  of  extract,  about  two-thirds  of  which  is  composed  of  a  resin"  giving 
the  bitter  flavour  and  acting  as  an  antiseptic  towards  certain  bacteria  injuriously  affecting  the 
keeping  of  the  beer,  although  it  has  no  influence  on  the  yeast.  The  flavour  of  the  beer  is  also 
considerably  affected  by  the  tannin  contained  in  the  hop  to  the  extent  of  2  to  4  per  cent. 

The  determination  of  the  ethereal  extract  is  also  employed  in  judging  of  the  quality  of  hops ; 
with  good  qualities,  after  evaporation  of  the  ether,  27  to  28  per  cent,  of  residue  is  left  (see  above, 
Lintner  Test). 

Germany  imported  2800  tons  of  hops  in  1908  and  2636  tons  in  1909,  the  exports  being  12,400 
and  8800  tons  respectively  in  1908  and  1909.  The  United  States  imported  2800  tons  in  1911 
and  exported  7000  tons. 

The  International  Agricultural  Institute  of  Rome  gives  the  following  statistics  of  hop 
production  : 


TT  ftons    . 

Hungary     {  hectarfcs 


Belgium 


France     . 

Great 
Britain 

Russia 

United 

States 


/ tons    . 
\hectares 

( tons    . 
\hectares 

/ tons     . 
\hectares 

tons    . 

/ tons     . 
\  hectares 


1908 

1910 

1911 

1912 

1913 

1914 

1915 

26,340 
35,865 

20,411 
27,460 

10,628 
26,658 

20,563 
26,966 

10,618 

27,048 

23,237 

27,685 

14,563 
23,737 

18,748 
25,364 

16,512 
21,281 

8,613 
19,919 

20,146 
20,304  ' 

8,564 
20,260 

16,444 

18,480 

— 

867 
1,142 

834 
926 

1,153 
1,357 

1,796 
2,176 

— 

, 

~ 

3,863 
2,060 

3,102 

2,047 

3,075 
2,101 

4,612 
2,283 

3,355 
2,405 

2,485 

— 

5,157 
3,030 

3,232 
2,741 

2,630 
2,843 

3,973 

2,832 

3,568 
2,951 

3,191 
2,731 

2,227 
2,214 

23,916 
15,751 

15,377 
13,308 

16,664 
13,377 

18,971 
14,095 

12,987 
14,437 

25,770 
14,836 

12,935 
14,060 

4,428 

2,949 

3,293 

4,423 

7,699 

6,388 

— 

19,913 

22,514 

23,438 

24,208 

28,530 

19,693 

26,907 

Whole         /  tons     . 
world       \hectares 


103,894       85,784       70,015       99,635       77,022       96,725       82,599 
84,000        68,515       67,000       69,489       69,068       71,586       66,875 


The  output  of  hops  per  hectare  (2-47  acres)  varies  from  14  to  30  cwt. 

Australia  produces  800  to  900  tons  of  hops,  the  area  under  their  cultivation  being  500  to  600 
hectares. 


STEEPING 


195 


malt  and  hops.     Iron  is  also  harmful,  and  especially  so  are  waters  contaminated  with 
bacteria.1 

The  principal  operations  in  the  manufacture 
of  beer  are  as  follow  : 

(1)  CLEANING     OF    THE     BARLEY,     to 
remove    dust,    soil,   stones,'  damaged    and    light 
corns,  etc.,  by  means  of  sieves,  fans,  etc. 

(2)  STEEPING  OF  THE  BARLEY  for  two 
or  three  days  in  water  at  11°  to  12°  in  order  that  it 
may  absorb  the  water  necessary  for  germination 
(about  45  per  cent.). 

For  this  purpose  use  is  generally  made  of  the 
Neubecker  tank  (Fig.  155),  made  of  iron  plates, 
open  at  the  top  and  cone-shaped  at  the  bottom. 
In  the  middle  is  a  wide  perforated  pipe,  E,  which 
is  surrounded  by  the  barley  (500  to  3000  kilos). 
The  water  is  supplied  by  the  pipe  W ,  and  is 
discharged  through  the  perforations  of  E,  thus 
covering  the  barley ;  it  is  then  discharged  from  the 
top  of  the  tank  through  the  pipe  U,  the  lighter 


FIG.  155. 


1  Water  for  brewing  should  contain  only  small  proportions  of  carbonates,  since  these  partially 
neutralise  the  primary  phosphates  of  the  wort,  whereas  for  the  enzymic  functions  inherent  to 
the  mashing  of  the  malt  the  acidity  of  the  malt  (primary  phosphates)  should  be  preserved. 
The  mashing  process  is  characterised  by  the  degradation  of  the  starch  by  diastase  and  by  the 
decomposition  of  the  protein  substances  by  means  of  peptases.  The  secondary  phosphates  are 
alkaline  to  methyl  orange  (the  primary  phosphates  being  neutral)  and  hinder  these  enzymic 
processes. 

Carbonates  tend  to  diminish  the  acidity,  thus  :  4KH2P04  +  3CaC03  =  3C02  +  3H20  + 
Ca3(P04)2  +  2K2HP04.  Sulphates,  however,  tend  to  restore  the  acidity  and  transform  the 
secondary  into  primary  phosphates  :  4K2HP04  +  3CaS04  =  Ca2(P04)2  +  JSKjSOj  +  2KH2P04 ; 
the  beneficial  effect  of  gypsum  is  thus  explained. 

The  carbonates  (calcium  bicarbonate)  may  be  eliminated  by  boiling  the  water  or  by  passing 
air  for  half  ah  hour  through  the  water  at  85°,  all  the  calcium  carbonate  and  most  of  the 
magnesium  carbonate  being  thus  deposited ;  if  the  temperature  is  lowered  to  60°  magnesium 
carbonate  redissolves,  so  that  the  water  should  be  filtered  hot.  The  cautious  decomposition  of 
the  carbonates  with  mineral  acids  or,  better,  with  lactic  acid  has  been  suggested. 

The  proportion  of  gypsum  present  in  the  water  is  often  increased  artificially.  For  pale 
beers  (Pilsener)  the  water  is  preferably  less  hard,  even  though  it  contains  only  little  gypsum. 
Excess  of  the  latter  affects  the  flavour  of  the  beer,  as  it  is  left  finally  as  potassium  sulphate  (see 
above),  which  has  a  decided  taste ;  this  is  readily  observed  on  adding  20  to  25  grams  of  potassium 
sulphate  per  hectolitre  to  beer  made  with  a  moderately  soft  water. 

In  the  case  of  dark  beers  the  influence  of  the  salts  of  the  water  is  less  apparent,  since  the 
torrefied  malt  is  more  acid  and  the  caramel  and  sugar  impart  to  the  beer  a  marked  taste,  which 
masks  other  flavours.  Even  for  dark  beers,  however,  a  water  of  only  moderate  hardness  is  to 
be  preferred. 

The  water  of  the  Munich  breweries  contains  a  medium  proportion  of  carbonates  (the  residue, 
28  grams  per  hectolitre,  contains  25  grams  of  carbonates)  and  very  little  gypsum ;  artificial 
increase  of  the  latter  is,  however,  never  suggested,  although  common  in  Britain. 

Also  for  steeping  barley  a  moderately  hard  water  is  best. 

The  compositions  of  various  waters  are  as  follows  (parts  per  1,000,000)  : 


Good 

Medium 

Bad 

Dry  residue         ...... 

250-450 

450-550 

550-700 

Ferric  oxide  and  alumina  (Fe203,Al2O3) 

0-1-5 

1-5-2-5 

3 

Lime  (CaO)         

120-150 

150-200 

200-300 

Magnesia  (MgO)            ..... 

20-50 

50-80 

80-120 

Sulphuric  acid  (S03)     

20-60 

60-80 

100-200 

Ammonia             .          . 

— 

— 

trace-1-5 

Nitrites  and  Nitrates   ..... 

— 

0-0-5 

0-5-1-5 

Organic  matter  (as  oxygen  absorbed) 

0-4-1-5 

1-5-2-0 

2-3 

Hardness  (French  degrees)    .... 

15-25 

25-35 

35-50 

Number  of  bacteria  per  1  c.c. 

50--500 

500-4000 

4000-10,000 

These  numbers  are  only  indicative  and  must  not  be  taken  too  strictly. 


196 


ORGANIC    CHEMISTRY 


floating  corns  being  carried  away.  After  seven  or  eight  hours  the  water  is  run  off  through 
the  tap  C,  and  the  moist  barley  left  exposed  to  the  air  for  five  or  six  hours.  Fresh  water  is 
then  introduced  and  left  for  ten  to  twelve  hours,  after  which  it  is  run  off  and  the  grain 
exposed  for  five  or  six  hours,  and  so  on.  This  procedure  is  continued  for  thirty  to  fifty 
hours  in  summer  or  seventy  to  one  hundred  hours  in  winter,  the  corns  having  in  that  time 
absorbed  about  40  per  cent,  of  water.  Steeping  of  the  barley  in  lime-water  has  been 
suggested  as  a  means  of  preventing  abnormal  fermentations  (Windisch,  1901)  and  of 
obtaining  beer  of  improved  aroma  and  flavour.  In  some  cases  steeping  is  preceded  by 
washing  of  the  barley  in  running  water  in  rotating  cylinders,  or  else  compressed  air  is 
forced  into  the  steeping  vessels  at  frequent  intervals,  so  as  to  stir  the  barley.  The  steep- 
water  becomes  yellowish  brown  and  acid,  and  after  some  time  undergoes  lactic  and  butyric 
fermentations.  At  the  end  of  the  operation,  the  barley  is  discharged  through  the  lower 
aperture,  A,  by  undoing  the  screw,  B,  and  raising  the  tube  E,  by  means  of  the  lever,  D. 

(3)  GERMINATION  OF  THE  BARLEY.  The  steeped  barley  is  carried  to  the  spacious 
malting  floor,  which  is  fitted  with  numerous  windows  to  allow  of  the  renewal  of  the  air  when 
desired,  and  is  arranged  so  that  the  temperature  may  be  maintained  constant  at  12°  to  16° ; 
this  end  is  often  attained  by  the  use  of  semi-underground  cellars,  which  should,  however, 
be  well  ventilated.  On  the  impermeable  floor  (of  cement  or  asphalte),  the  barley  is  spread 
out  in  a  layer  50  to  60  cm.  deep,  and  on  the  second  day  the  mass  is  moved  with  wooden 
shovels  so  as  to  reduce  the  depth  to  30  to  35  cm.,  this  being  further  reduced  to  15  cm.  on 
the  third  day.  Every  eight  or  ten  hours  the  grain  is  turned,  the  floor  being  kept  well 
ventilated.  The  temperature  gradually  rises,  but  should  not  be  allowed  to  exceed  20° ;  if 
necessary  it  may  be  moderated  by  turning  more  often  and  thinning  out  the  barley.  After  the 

second  day  the  radicles  begin  to  sprout  and 
later  the  plumule.  In  eight  to  ten  days  the 
rootlets  become  twice  or  three  times  as  long  as 
the  corn  and  the  transformation  of  nitrogenous 
material  into  diastase  is  at  its  maximum 
(Fig.  156  shows  the  various  stages  in  the  ger- 
mination of  barley).  The  germination  should 
then  be  interrupted  so  as  not .  to  lose  any 
part  of  the  diastase  formed,  the  green  malt 
then  containing  about  40  per  cent,  of  moisture. 
A  floor  of  20  sq.  metres  is  sufficient  for  only  1000  litres  of  steeped  grain.  If  the  piece  dries 
too  much,  it  is  moistened  by  sprinkling  with  water.  In  order  to  prevent  mould-growth 
when  the  floor  is  free,  it,  and  also  the  walls,  are  washed  with  1  per  cent,  calcium  bisulphite 
solution,  the  floors  being  then  well  dried  by  ventilation.1 

The  germination  is  now  sometimes  carried  out  on  the  pneumatic  system,  use  being 
made  of  the  Galland  apparatus  (Figs.  157  and  158),  which  consists  of  a  double  sheet-iron 
drum,  T,  rotated  by  means  of  the  wheels,  b  (two  rotations,  each  occupying  forty  minutes, 
every  six  to  eight  hours).  The  inner  drum  is  perforated  and  is  filled  to  the  extent  of  four- 
fifths  with  barley  from  the  steeping  tank,  W ;  along  the  axis  of  the  cylinder  passes  a  pipe 
which  is  also  perforated.  Air  sucked  in  by  a  fan,  Z,  is  moistened  in  A  by  means  of  pulverised 
water,  and  from  L  passes  into  the  jacket  of  the  drum,  then  through  the  perforations  and  the 

1  In  Germany  beer  must  be  made  from  malted  barley  alone;  in  1912  the  German  breweries 
used  1,300,000  tons  of  barley  (almost  exclusively  two-rowed),  of  which  a  small  part  only  was 
imported  from  Austria. 

Barley  contains  60  to  70  per  cent,  of  starch,  0-5  to  2  per  cent,  of  saccharose,  2  to  3  per  cent, 
of  fat,  and  8  to  14  per  cent,  of  proteins. 

At  least  95  per  cent,  of  the  barley  corns  should  germinate  (germinative  capacity),  the 
germinative  power,  i.e.,  the  rapidity  of  germination,  also  being  of  importance;  with  a  good 
barley,  not  less  than  95  per  cent,  of  the  corns  should  germinate  within  three  days.  A  barley 
with  a  germinative  capacity  of  85  to  90  per  cent.,  and  a  similar  germinative  power  is  preferable 
to  one  having  a  germinative  capacity  of  100  per  cent,  and  a  germinative  power  of  only 
70  per  cent. 

In  general  barley  rich  in  proteins  is  poor  in  starch  and  hence  yields  a  malt  of  low  extract, 
whereas  protein-poor  barley  is  rich  in  starch  and  gives  a  malt  yielding  a  high  extract.  During 
mashing  the  starch  passes  almost  completely  into  solution,  whilst  only  about  one-third  of  the 
protein  substances  is  dissolved,  the  remaining  two-thirds  being  found  in  the  grains. 

Barley  contains  a  diastase  capable  of  saccharifying  dissolved  starch,  but  incapable  of  dissolving 
starch ;  the  latter  end  is  attained  by  means  of  the  diastase  formed  during  the  germination  of 
the  barley. 


FIG.  156. 


GROWING    OF    MALT 


197 


grain  to  the  central  pipe,  TO.  Thence  it  proceeds  to  8,  and  so  through  the  fan  Z  to  the  shaft ; 
a  thermometer  here  shows  the  temperature  of  the  air,  and  if  this  becomes  too  high  the  speed 
of  the  fan  is  increased.  If  100  kilos  of  barley  is  taken  and  the  air  enters  at  12°  and  issues 
at  20°,  4500  cu.  metres  of  air  is  required  per  hour;  if  the  air  is  to  leave  at  16°,  10,000  cu. 
metres  per  hour  is  necessary.  The  germination  lasts  eight  to  nine  days. 


FIG.  157. 


FIG.  158. 


To  stop  the  germination,  a  current  of  dry  air,  heated  to  22°  to  25°  or  mixed  with  gas 
rich  in  CO2  (to  diminish  the  supply  of  oxygen),  is  supplied;  in  a  short  time  the  moisture 
content  of  the  grain  is  reduced  from  40  per  cent,  to  20  to  25  per  cent. 

For  a  malting  to  give  continuously  2000  to  5000  kilos  per  day,  three  to  four  steeping-tanks 
are  used,  these  feeding  six  to  eight  Galland  drums  arranged  in  batteries  (Fig.  159) ;  6  to  10 
horse-power  is  required  for  turning  the  drums,  driving  the  fans,  etc. 


FIG.  159. 

The  water  necessary  for  steeping  amounts  to  about  10  to  12  times  the  weight  of 
the  barley,  rather  less  being  required  to  moisten  the  air  for  pneumatic  malting.  The  steep- 
water  may  hence  be  used  again  for  the  latter  purpose  if  at  any  time  the  water-supply 
is  scarce. 

Another  system  of  malting,  used  especially  in  France,  is  that  of  Saladin  (shown  in 
perspective  in  Fig.  160,  while  Fig.  161  shows  a  longitudinal  section  of  one  of  the  vessels, 


198 


ORGANIC    CHEMISTRY 


and  Fig.  162  a  transverse  section  of  the  vessels).  There  is  one  vessel,  made  of  concrete 
and  fitted  with  a  perforated  false  bottom  of  sheet-iron,  for  each  day  that  the  germination 
lasts  (eight  to  nine  days).  These  vessels,  B,  communicate  under  the  false  bottom  with  a 
channel  containing  a  fan  which  draws  moistened  air  through  the  mass  of  barley  in  the  vessel 
(50  cm.  deep).  Above  each  vessel  is  a  slow  mechanical  turner,  A,  with  a  number  of  screws 
which  rotate  in  the  barley  as  the  turner  passes  along  the  vessel.  The  turner  may  be  trans^ 
ported  from  one  vessel  to  another  and  is  put  into  operation  twice  a  day  at  first  (the  tempera- 
ture of  the  barley  being  12°  to  14°),  then  four  times  a  day  (at  15°  to  18°),  and  finally  twice 
a  day  (at  18°  to  15°).  In  some  maltings  a  saving  is_effected  by  operating  the  fan  only  at 


FIG.  160. 

intervals — when  the  temperature  rises.  Dry  air,  drawn  along  the  channels,  8,  is  finally 
passed  through  the  malt. 

The  advantages  of  the  various  mechanical  processes  over  the  old  system  of  malting 
are  that  they  may  be  worked  continuously  and  at  any  season  of  the  year,  while  they  occupy 
less  space,  allow  of  efficient  regulation  of  temperature,  economise  labour  and  general  expenses 
and  diminish  the  percentage  of  waste. 

(4)  KILNING  OF  MALT.  The  germinated  barley  is  too  moist  to  keep  sound,  and 
as  breweries  require  large  stocks  of  malt  this  must  be  dry  and  capable  of  being  kept.  If 
the  moisture  is  reduced  to  6  per  cent,  by  air  alone  the  germination  process  is  stopped,  and 
on  subsequently  raising  the  temperature  to  60°  a  slight  diastatic  saccharification  occurs, 


1 

I 

p 

p~ 

®[7r^)A 

(Sri 

*-,0^ 

\ 

"1 

i 

1 

1 

:  « 

QDnTJOOGTinDDCtinn 

3DCDDDDOOD 

'      L      r  1  '  1 

i       |c      L  i     1 

s- 

• 

FIG.  161. 


FIG.  162. 


this  being  greater  in  amount  if  the  moisture  is  kept  at  12  to  15  per  cent. ;  beyond  70°  the 
diastase  is  destroyed  and  certain  substances  formed  which  give  good  flavour,  aroma  and 
fullness  of_taste  to  the  beer  and  at  the  same  time  furnish  food  for  the  yeast.  When  the 
temperature  exceeds  100°  part"of  the  maltose  is  caramelised — for  the  making  of  dark  beers 
— and  a  considerable  amount  of  nitrogenous  substances,  which  would  cause  the  beer  to 
keep  badly,  rendered  insoluble. 

In  order  not  to  destroy  too  much  of  the  diastase  and  to  make  malt  suitable  for  pale 
beers  the  drying  must  first  be  conducted  with  only  slightly  warm  air.  When  the  proportion 
of  moisture  has  reached  5  to  6  per  cent,  the  diastase  is  able  to  withstand  a  temperature  of 
60°  to  70°  without  losing  much  of  its  activity,  whilst  if  the  malt  is  heated  when  it  contains 
too  much  moisture  (15  to  20  per  cent.)  the  diastase  is  rapidly  destroyed.  The  drying  is 
carried  out  in  a  current  of  warm  air  (or  of  air  mixed  with  the  hot  gases  from  a  coke  or 


KILNING    OF    MALT 


199 


anthracite  fire),  which  passes  through  the  green  malt  placed  in  layers  15  to  20  cm.  deep  on 
wire  or  tile  floors,  often  arranged  one  above  the  other.  Above  the  upper  floor  is  a  chimney, 
which  increases  and  facilitates  the  draught  started  by  suitable  fans.  The  air  is  heated  by 
passing  directly  over  a  fire  or  through  batteries  of  tubes  heated  in  the  usual  way.  During 
the  drying  the  malt  is  turned  by  a  suitable  mechanical  device,  at  first  every  two  hours  and 
later  on  continuously.  The  temperature  of  the  air  gradually  rises,  during  the  course  of 
eighty-four  to  ninety  hours,  by  30°  to  35°  (during  the  first  few  hours  germination  still  pro- 
ceeds feebly,  causing  increase  in  the  diastase),  and  ends  at  100°  to  110°  (for  dark  beers). 
Drying  is  usually  effected  in  less  than  forty-eight  hours,  and  it  is  only  beyond  80°  that  the 
diastase  partially  loses  its  saccharifying  properties  (at  90°  it  loses  50  per  cent,  and  at  100° 
85  per  cent. ) ;  this  loss  is,  however,  an  advantage,  since  a 
too  highly  diastatic  malt  leads  to  excessive  saccharification 
and  hence  to  increased  attenuation  in  the  subsequent 
fermentation,  so  that  the  beer  tastes  less  full.  The  peptases 
also  are  destroyed  beyond  90°,  so  that  the  nitrogenous 
substances  are  dissolved  to  a  less  extent  and  the  beer  hence 
keeps  better. 

Fig.  163  shows  diagrammatically  a  section  of  a  two- 
floor  malt-kiln  in  which  the  air  is  heated  in  the  tubing,  t, 
surrounding  the  ducts  carrying  the  hot  fumes  from  the  coal 
burning  on  the  grate,  F.  The  hot  air  then  traverses  the 
malt  on  the  floors,  B  and  C,  and  issues  from  the  chimney, 
D,  the  turning  apparatus,  a,  being  kept  in  motion  mean- 
while. To  obtain  100  kilos  of  dry  malt  in  twenty-four 
hours  (maximum  temperature  90°  to  100°)  20  kilos  of  coal 
are  required.  For  making  dark  beers  of  the  Munich  type 
part  of  the  kilned  malt  is  further  roasted  at  about  200°  in 
suitable  rotating  iron  cylinders  heated  by  direct  fire ;  this 
treatment  leads  to  the  formation  of  caramel,  which  colours 
the  beer,  the  malt  being  then  called  coloured  malt.  The 
temperatures  on  the  malting-floors  and  kiln  are  registered 
by  automatic  devices  which  construct  diagrams  showing 
the  temperature  at  any  particular  moment. 

Nowadays  malt  for  pale  beers  is  sometimes  heated  only 
to  25°  to  30°. 

The  kilned  malt  leaves  the  kiln  with  2  to  5  per  cent,  of  moisture,  and  is  then  cooled  and 
stored  in  silos  or  large  bins.  A  malt  kept  for  only  one  or  two  months  is  to  be  preferred  to  an 
older  one.1 

1  The  commercial  value  of  a  malt  is  determined  largely  by  its  yield  of  extract,  which  is  measuied 
as  follows  :  45  grams  of  ground  malt  are  placed  in  a  tared  flask  with  200  c.c.  of  water,  the 
temperature  being  kept  at  exactly  45°  for  half  an  hour  and  then  raised  1°  per  minute  up  to  70°, 
this  temperature  being  maintained  until  the  liquid  no  longer  gives  a  blue  colour  with  iodine; 
the  time  required  at  70°  to  reach  this  point  is  noted  (saccharification  test}.  The  mass  is  then 
cooled  and  water  added  to  bring  its  total  weight  up  to  450  grams;  after  mixing  and  filtering 
through  a  dry  filter,  the  density  of  the  liquid  is  determined  at  15°  and  by  Windisch's  or  Schulze's 
tables  the  corresponding  quantity  of  extract  deduced.  The  latter  may  also  be  obtained  from 
Balling's  tables  (see  below),  note  being  taken  that  they  yield  low  values,  the  deficit  being  0-08 
gram  per  cent,  for  specific  gravities  up  to  1-01 ;  0-345  for  specific  gravities  up  to  1-05;  0-48  for 
specific  gravities  up  to  1-06;  and  0-4  for  specific  gravities  up  to  1-08.  If  the  maltose  is  to  be 
determined  directly,  10  grams  of  the  filtered  saccharine  liquid  (corresponding  with  1  gram  malt) 
are  diluted  to  100  c.c.,  various  quantities  of  this  liquid  being  then  titrated  with  Fehling's 
solution,  1  c.c.  of  which  corresponds  with  0-0075  gram  of  maltose. 

C.  Lintner  (1886-1908)  has  modified  the  Kjeldahl  method  for  determining  the  diavtatic  power 
of  malt  as  follows  :  25  grams  of  the  ground  malt  are  extracted  for  6  hours  with  500  c.c.  of  water 
at  the  ordinary  temperature,  the  mixture  then  being  filtered;  2  c.c.  (for  pale  malts)  or  8  c.c. 
(for  dark  malts)  of  the  filtrate  is  added  to  100  c.c.  of  2  per  cent,  soluble  starch  solution  and  the 

N 
mixture  left  for  exactly  half  an  hour,  at  the  end  of  which  time  10  c.c.  of  .^  caustic  soda  solution 

is  added.  Into  a  number  of  test-tubes,  each  containing  5  c.c.  of  Fehling's  solution,  are  intro- 
duced varying  quantities  of  the  saccharified  starch  solution  (e.  g.,  from  1  to  6  c.c.);  the  tubes 
are  next  immersed  for  ten  minutes  in  a  boiling  water-bath  and  then  taken  out,  and  the  pre- 
cipitated cuprous  oxide  allowed  to  settle ;  it  can  then  be  seen  in  which  of  the  tubes  the  Fehling's 
solution  is  just  completely  reduced  and  in  which  it  is  just  not  reduced.  A  more  exact  result 


FJG.  163. 


200 


ORGANIC    CHEMISTRY 


Malt  kilned  with  fumes  direct  from  a  coal  fire  communicates  to  the  beer  a  certain 
flavour  from  the  smoke.  Also,  when  coal  is  employed  which  contains  arsenic,  the  latter 
becomes  deposited  on  the  malt  and  hence  finds  its  way  into  the  beer.  Arsenic  may  also 
be  present  in  the  glucose  often  used  in  brewing ;  in  this  case  it  is  introduced  by  the 
employment  of  arsenical  sulphuric  acid  in  the  manufacture  of  the  glucose  from  starch. 

(5)  CLEANING  AND  GRINDING.  Before  the  malt  is  mashed  it  is  freed  from  dust 
and  rootlets  by  means  of  rotating  drums  of  metal  gauze  (a  kind  of  sieve)  furnished  with 
fans.  It  is  then  ground,  but  not  too  finely,  the  husks  being  kept  whole  as  far  as  possible, 
since  they  serve  in  the  subsequent  operations  as  filtering  material ;  if  the  malt  is  ground 
too  fine  it  cannot  be  exhausted,  as  the  liquid  will  not  drain  off.  A  suitable  form  of  mill  is 
the  Excelsior  Mill,  made  by  Messrs.  Krupp  (Figs.  164  and  165).  The  shaft,  g,  fitted  with 
fast  and  loose  pulleys,  s  and  t,  may  be  shifted  from  right  to  left  or  vice  versa  through  the 
stuffing-boxes,  m,  by  means  of  the  lever,  d.  One  toothed  disc,  a,  is  fixed,  whilst  the  other, 
b,  rotates  with  the  axis,  g,  and  is  so  adjusted  that  the  teeth  pass  through  the  tooth  spaces 
of  the  other  disc.  The  malt  from  the  hopper,  /,  falls  between  the  two  discs,  where  it  is 

may  be  obtained  by  using  quantities  of  the  saccharified  starch  solution  intermediate  to  those 
corresponding  with  these  two  tubes.  When  0-1  c.c.  of  the  cold  water  malt  extract,  acting  for 
one  hour  on  10  c.c.  of  2  per  cent,  soluble  starch  solution,  forms  just  sufficient  maltose  to  reduce 
6  c.c.  of  Fehling's  solution,  the  malt  is  said  to  have  the  diastatic  power  100 ;  if  0-2  c.c.  of  the  malt 
extract  is  required,  the  diastatic  power  is  taken  as  50,  and  so  on. 

BALLING'S  TABLE 


Sp.  gr. 
at  17-5° 

Degrees 
Balling  or 
grams  of 
saccharose 

Sp.  gr. 
at  17'5° 

Degrees 
Balling  or 
grams  of 
saccharose 

Sp.  gr. 
at  17-5° 

Degrees 
Balling  or 
grams  of 
saccharose 

Sp.  gr. 

at  17-5° 

Degrees 
Balling  or 
grams  of 
saccharose 

per  100 
grams  liquid 

per  100 
grams  liquid 

per  100 
grams  liquid 

per  100 
grains  liquid 

1-0010 

0-250 

1-0210 

5-250 

1-0410 

10-142 

1-0610 

14-904 

1-0020 

0-500 

1-0220 

5-500 

1-0420 

10-381 

1-0620 

15-139 

1-0030 

0-750 

1-0230 

5-575 

1-0430 

10-619 

1-0630 

15-371 

1-0040 

1-000 

1-0240           6-000 

1-0440 

10-857 

1-0640 

15-604 

1-0050 

1-250 

1-0250           6-244 

1-0450 

11-095 

1-0650 

15-837 

1-0060 

1-500 

1-0260 

6-488 

1-0460 

11-333 

1-0660 

16-070 

1-0070 

1-750 

1-0270 

6-731 

1-0470 

11-571 

1-0670 

16-302 

1-0080 

2-000 

1-0280 

6-975 

1-0480 

11-809 

1-0680 

16-534* 

1-0090 

2-250 

1-0290 

7-219 

1-0490 

12-047 

1-0690 

16-767 

1-0100 

2-500 

1-0300 

7-463 

1-0500 

12-285 

1-0700 

17-000 

1-0110 

2-750 

1-0310 

7-706 

1-0510 

12-523 

1-0710 

17-227 

1-0120 

3-000 

1-0320 

7-950 

1-0520 

12-761 

1-0720 

17-454 

1-0130 

3-250 

1-0330 

8-195 

1-0530 

13-000 

1-0730 

17-681 

1-0140 

3-500 

1-0340 

8-438 

1-0540 

13-238 

1-0740 

17-909 

1-0150 

3-750 

1-0350 

8-681 

1-0550 

13-476 

1-0750 

18-136 

1-0160 

4-000 

1-0360 

8-925 

1-0560          13-714 

1-0760 

18-363 

1-0170 

4-250 

1-0370 

9-170 

1-0570 

13-952 

1-0770 

18-590 

1-0180 

4-500 

1-0380 

9-413 

1-0580 

14-190 

1-0780 

18-818 

1-0190 

4-750 

1-0390 

9-657 

1-0590 

14-428 

1-0790 

19-045 

1-0200 

5-000 

1-0400 

9-901 

1-0600 

14-666 

1-0800 

19-272 

Correction  of  Degrees  Balling  for  Various  Temperatures 


Determin- 
ation made 
at  tsmpera- 
ture  of 

Correction 
of  degrees 
Balling 

Determina- 
tion made 
at  tempera- 
ture of 

Correction 
of  degrees 
Balling 

XSSe"   SssS 

attempera-       «£&. 

Determina- 
tion made 
at  tempera- 
ture of 

Correction 
of  degrees 
Balling 

f 

Deg. 

Deg. 

Deg. 

Deg. 

4 

-0-43 

11 

-0-22 

17-5 

24 

+  0-27 

5 

-0-40 

12 

-0-19 

18             +  0-02 

25 

+  0-32 

6 

-0-37 

13 

-0-16 

19             +0-05 

26 

4  0-37 

7 

-0-34 

14 

-0-13 

20             +  0-09 

27 

+  0-42 

8 

-0-31 

15 

-0-10 

21              +0-13 

28 

+  0-48 

9 

-0-28 

16 

-0-06 

22             +0-17 

29 

+  0-54 

10 

-0-25 

17 

-0-02 

23             +  0-22 

30 

+  0-60 

MASHING 


201 


ground,  the  ground  malt  (grist)  being  discharged  at  n.  For  the  sake  of  economy  the  discs 
are  toothed  on  both  faces,  so  that  when  one  face  is  worn  the  other  may  be  used. 

The  total  loss  in  weight  suffered  by  the  barley  during  steeping,  germination,  kilning, 
cleaning,  and  grinding  amounts  to  about  20  per  cent. 

(6)  MASHING.  This  consists  in  subjecting  the  ground  malt  to  the  action  of  warm 
water  so  that  the  diastase  may  act  on  the  starch  and  convert  it  into  soluble  products.  The 
temperature  at  which  the  maximum 
extract  is  obtained  is  about  65°,  whilst 
at  55°  the  starch  is  only  very  slightly 
attacked  by  diastase,  and  above  70° 
diastase  loses  its  saccharifying  pro- 
perties very  largely  and  the  wort 
niters  through  the  grains  (husks;  see 
later)  with  difficulty — this  effect  is 
aggravated  by  coagulation  of  part 
of  the  proteins.  The  quantity  and 
quality  of  the  water  have  an  influence 
on  the  mashing,  the  presence  of 
calcium  sulphate  facilitating  the  for- 
mation of  maltose  and  maltodextrins 
and  increasing  the  amount  of  nitro- 
genous substances  dissolved.  From  1 
ton  of  malt  20  to  30  hectolitres  of  beer 
are  made. 

There  are  two  systems  of  mashing : 
the    infusion    method    (at    65°    to  FIG.  164. 

72°),  used  only  in  top-fermentation 

breweries,  and  the  decoction  system,  used  for  bottom-fermentation  and  sometimes  for 
top-fermentation  beers,  and  with  highly  diastatic  malt  or  when  unmalted  barley  is  used 
with  the  malt. 

(I)  The  infusion  process,  used  largely  in  England  and  Scotland,  less  in  France  and 
still  less  in  Germany,  is  usually  carried  out  in  one  of  two  ways  :  (i)  Rising  infusion,  where 
the  malt  is  first  mixed  to  a  paste  with  10  per 
cent,  of  cold  water  and  then  with  hot  water 
"in  the  ratio  of  two  parts  of  water  to  one 
part  of  malt,  so  that  a  temperature  of  40°  is 


FIG.  165. 

attained.  To  raise  the  temperature  of  1  kilo  of  malt  (which  has  a  specific  heat  of  about 
0-5)  from  20°  to  40°  requires  10  Calories,  which  can  be  supplied  by  2  litres  of  water  at 
45°,  the  latter  falling  to  40°  on  losing  10  Calories;  owing,  however,  to  unavoidable  loss 
of  heat,  water  at  48°  to  50°  should  be  used. 

This  mixing  is  done  in  a  circular  mash-tun  of  metal  or  wood,  furnished  with  a  perforated 
false  bottom  several  centimetres  above  the  true  bottom,  in  which  are  fitted  the  pipes 
supplying  the  hot  water  (Fig.  166).  The  mashing  and  subsequent  mixing  are  effected 
by  efficient  mechanical  stirrers  or  rakes. 


202 


ORGANIC    CHEMISTRY 


As  soon  as  the  mash  has  reached  the  temperature  of  40°  water  at  80°  is  gradually 
introduced,  the  temperature  being  raised  to  63°  to  65°  in  half  an  hour.  It  is  next 
mixed  for  sixty  to  seventy  minutes,  the  liquid  being  then  discharged  by  opening  the 
taps  under  the  false  bottom  so  that  the  liquid  passes  through  the  grains  and  is  conducted 
to  the  copper.  The  residue  in  the  tun  is  mixed  for  fifteen  minutes  with  water  at  75°,  the 
liquid  being  run  off  and  the  grains  finally  washed  with  water  at  85°,  all  these  extracts 
passing  to  the  copper.  In  this  way  almost  complete  saccharification  is  attained  and  the 
subsequent  fermentation  produces  considerable  attenuation.  If  a  less  attenuation  is 
desired,  either  a  higher  temperature  (72°  to  73°)  is  used  in  place  of  65°,  or  high-dried 
malt  is  used. 

(ii)  Descending  infusion,  which  is  rarely  used,  consists  in  bringing  the  mass  directly  to  a 
temperature  of  65°  to  70°  with  very  hot  water  and  then  allowing  it  to  fall  slowly  to  35° 
to  40°. 

Neither  of  these  methods  admits  of  the  use  of  rice  or  maize,  the  starch  of  which  is 
attacked  by  diastase  only  after  the  starch  has  been  heated  with  water  to  80°  to  85°.  Hence 
with  such  material  the  decoction  process  is  used. 


FIG.  167. 

(II)  Decoction  Process.  This  is  largely  used  in  North  Germany,  Austria,  and  Belgium, 
and  allows  of  the  use  of  unmalted  barley,  rice,  maize,  wheat,  etc. 

The  malt  grist  is  first  mixed  to  a  paste  with  cold  water  so  as  to  dissolve  the  diastase, 
this  being  carried  out  in  a  metal  vessel  without  a  false  bottom ;  by  the  addition  of  small 
quantities  of  boiling  water  the  temperature  of  the  mass  is  raised  gradually  to  35°.  From 
one-third  to  one-half  of  the  turbid  wort  (Dickmaische)  is  transferred  to  a  double-bottomed 
copper  heated  with  steam.  In  many  cases  coppers  with  direct-fire  heat  are  used,  these 
being  furnished  with  chains  which  scrape  on  the  bottom  and  so  prevent  caramelisation  of 
the  mass  which  settles  (Fig.  167  shows  a  complete  decoction  or  infusion  plant).  The 
wort  transferred  to  the  copper  is  boiled  for  twenty  to  forty  minutes  and  is  then  returned  to 
the  original  tun,  where  it  raises  the  temperature  to  about  55°.  Another  one-third  or  one- 
half  is  similarly  removed,  boiled,  and  returned,  the  temperature  being  thus  raised  to  65° ; 
the  saccharification  has  then  reached  a  maximum  and  the  mash  become  thinner.  The 
complete  disappearance  of  starch  is  controlled  by  the  reaction  with  iodine.  About  one-half 
of  the  wort  is  again  removed,  boiled,  and  returned,  the  temperature  being  thus  raised  to 
75°.  During  all  these  operations  continual  stirring  is  maintained.  The  greater  the  number 
of  decoctions  made  the  greater  will  be  the  density  of  the  wort  and  the  darker  the  beer. 
The  turbid  wort  is  either  allowed  to  deposit  in  tuns  with  false  bottoms,  as  shown  in  Fig. 


BOILINGOFTHEWORT  203 

166,  or  passed  through  filter-presses  (see  Sugar  Industry)  to  clarify  it,  the  grains  remaining 
in  the  form  of  cakes  being  well  washed.1 

When  considerable  quantities  of  other  cereals  are  to  be  used  with  the  malt  use  is  made 
of  a  Henze  pressure  apparatus,  as  described  under  Distilling  (Fig.  106,  p.  142). 

The  wort  thus  obtained  is  boiled  with  a  certain  quantity  of  hops  until  a  certain  degree 
of  concentration  has  been  effected.  This  boiling  finally  destroys  the  diastase,  intensifies 
the  colour  of  the  wort  and  aerates  it,  and  oxidises  various  substances  producing  acid  bodies ; 
it  completely  sterilises  the  liquid,  which  is  also  clarified  owing  to  the  precipitation  of  nitro- 
genous substances,  partly  by  the  tannin  of  the  hops. 

The  decoction  of  the  hops  is  carried  out  in  a  separate  vessel,  the  boiling  liquid  being 
continually  circulated  until  the  hops  are  exhausted.  The  decoction  is  then  added  to  the 
boiling  wort,  principally  towards  the  end  of  the  operation ;  if  added  earlier  the  hop  extract 
loses  some  of  its  aroma.  Direct  addition  of  the  hops  to  the  copper  is  still  practised,  although 
the  method  is  not  a  very  rational  one ;  it  is  better  to  pass  the  boiling  wort  from  time  to  time 
into  a  separate  vessel  containing  the  hops  and  then  back  to  the  copper,  this  procedure 
being  repeated  until  the  hops  are  exhausted. 

In  general,  400  to  500  grams  of  hops  are  used  per  hectolitre  of  beer,  or  1-2  to  2'5  kilos  for 
every  cwt.  of  malt  mashed.  More  hops  are  usually  employed  for  beers  to.  be  kept  for 
some  time  (lager  beer,  stock  ale)  than  for  draught  beer,  and  more  for  beers  of  the  Pilsen  type 
than  for  those  of  the  Munich  type.  The  lupulin  powder  contained  in  the  hop  gives  up  resins 
and  essential  oils,  while  the  leaves  give  tannin  and  the  stalks  somewhat  bitter  substances ; 
the  whole  gives  the  bitter  taste  and  aroma  of  the  beer,  and  causes  the  latter  to  keep  better. 
A  temperature  of  75°  (Pasteur)  is  sufficient  to  sterilise  a  hopped  beer,  since  the  resins  have 
a  marked  antiseptic  action. 

The  boiling  of  the  wort  is  carried  out  in  copper  vessels  (see  Fig.  167,  a)  heated  by  direct 
fire  or  by  indirect  steam  (passed  through  coils  or  through  the  double  bottom  of  the  copper), 
the  boiling  being  continued  for  four  to  six  hours  with  dilute  worts  (infusion),  and  only  one 
and  a  half  to  two  hours  with  the  more  concentrated  decoction  worts ;  as  a  rule  boiling  is 
continued  until  the  density  reaches  a  certain  value  for  the  particular  kind  of  beer  to  be  made 
(see  later).  The  temperature  during  boiling  should  be  gradually  raised  and  registered.  In 
many  modern  breweries  there  are  automatic  registering  thermometers  which  show  the  whole 
course  of  these  operations.  When  the  boiling  is  finished  the  wort  is  allowed  to  stand  for  a 
time,  and  the  Inland  Revenue  officials  then  generally  make  their  first  measurements  (they 
calculate  that  1  kilo  of  dry  malt  should  give  25  litres  of  wort  with  a  density  of  1°  Balling, 
5  litres  at  5°,  etc.,  an  allowance  being  made  of  10  per  cent.).  The  copper  is  then  dis- 
charged, the  hops  being  strained  off,  and  the.  wort  pumped  to  the  cooler,  which  is  usually 
at  the  top  of  the  building.  These  coolers  are  large  shallow  vessels  of  iron  (or  copper  or 
wood )  in  which  the  coagulated  proteins  are  deposited ;  the  temperature  here  is  not  allowed 
to  fall  below  55°  to  60°,  otherwise  contamination  with  harmful  organisms  (butyric,  lactic, 
etc.)  might  occur.  In  Italy  the  tax  on  the  manufacture  of  beer  is  calculated  from  the 
volume,  temperature,  and  specific  gravity  of  the  wort  in  the  cooler  (see'later).  In  the  cooler, 
part  of  the  water  evaporates,  this  being  as  much  as  4  per  cent,  in  the  summer.  The  wort 
is  next  cooled  rapidly  by  suitable  refrigerators  to  2°  to  3°  (for  bottom  fermentation)  or 
12°  to  15°  (for  top  fermentation).  One  form  of  refrigerator  which  is  much  used  consists  of 
a  number  of  superposed,  communicating  horizontal  tubes  (Fig.  168).  In  the  tubes  of 
the  upper  half  water  circulates,  and  in  those  of  the  second  half  brine  at  a  temperature 
of  —  6°  or  —  8°  from  a  refrigerating  machine  (see  Vol.  I.,  p.  260).  The  wort  flows  down  in 
a  thin  skin  over  the  outside  of  the  tubes,  meanwhile  dissolving  an  appreciable  quantity 
of  air.  The  cooled  and  aerated  wort  flows  down  to  the  fermenting  vessels  placed  in  cool 
rooms;  for  bottom  fermentation  these  are  cooled  to  about  0°  by  pipes  conveying  cold 

1  The  grains  are  composed  of  the  whole  of  the  husks  of  the  malt,  coagulated  proteins, 
pentosans,  fat,  maltose,  and  dextrin.  They  serve  as  excellent  cattle-food,  biit  if  not  consumed 
in  the  course  of  24  hours,  they  undergo  change ;  they  may,  however,  be  placed  in  silos  or  dried 
in  a  suitable  apparatus  (see  Fig.  151,  p.  183).  Wet  grains  contain  70  to  80  per  cent,  of  water, 
4  to  6  per  cent,  of  protein,  1  to  3  per  cent,  of  fat,  8  to  14  per  cent,  of  extractive  substances, 
1  to  3  per  cent,  of  ash,  and  3  to  9  per  cent,  of  cellulose.  Dried  grains  contain  6  to  18  per  cent, 
of  water,  17  to  26  per  cent,  of  protein,  4  to  9  per  cent,  of  fat,  35  to  55  per  cent,  of  extractive 
substances,  3  to  12  per  cent,  of  ash,  and  9  to  20  per  cent,  of  cellulose ;  they  have  a  brown  colour, 
a  pleasing  odour  of  new  bread,  and  a  sweet  taste ;  they  make  a  good  fodder  to  follow  wheat  or 
oat  bran. 


204 


ORGANIC    CHEMISTRY 


brine.  The  wort  from  the  coolers  is  turbid  and  should  be  filtered  through  conical  cloth 
bags  or  filter-presses.  In  some  modern  breweries  the  coolers  are  omitted  in  order  to  avoid 
any  possible  contamination  (which  is,  however,  difficult  with  hopped  wort  at  60°)  and 
the  wort  is  passed  direct  from  the  copper  to  the  closed  refrigerator  and  the  filter-press, 
aeration  being  afterwards  effected  with  air  filtered  through  cotton-wool. 

The  refrigerators  consume  considerable  quantities  of  water,  and  where  this  is  scarce  the 
warm  water  from  the  refrigerators  is  cooled  by  means  of  pulverisers  or  by  causing  it  to  flow 
down  over  twigs,  the  evaporation  thus  caused  often  lowering  the  temperature  below  that  of 
the  air  (see  section  on  Sugar).  The  boiling  of  the  wort  has  hence  effected  a  concentration, 
the  preparation  of  a  sterile  (aseptic)  liquid,  and  the  extraction  of  the  useful  principle  of  the 
hop,  the  tannin  of  which  has  partially  precipitated  the  proteins.  If  pale  beer  is  to  be  brewed 
the  wort  may,  if  necessary,  be  clarified  during  the  boiling  by  the  addition  of  a  little  tannin. 
During  the  cooling  on  the  coolers  the  wort  takes  up  the  oxygen  necessary  for  the  oxidation 
of  the  resins,  for  clarifying  it  and,  more  especially,  for  aiding  the  development  and  multiplica- 
tion of  the  yeast  during  the  initial  stages 
of  the  fermentation. 

Contact  of  the  wort  with  tin,  e.  g., 
tinned  vessels,  is  to  be  avoided,  as 
turbidity « of  the  beer  may  be  caused 
thereby,  especially  if  the  wort  is  acid  or 
rich  in  carbon  dioxide. 

FERMENTATION.  From  the 
density  (degrees  Balling)  or  the  dry 
extract  of  the  wort,  the  extract 
yielded  by  the  materials  may  be 
deduced,  and,  under  favourable 
conditions,  the  dry  extract  amounts 
to  about  70  per  cent,  of  the  weight 
of  the  malt,  whilst  with  bad  working 
it  may  be  as  low  as  45  per  cent. 
When  ready  for  fermentation  the 
wort  contains  mainly  maltose,  malto- 
dextrinSj  dextrins,  a  little  saccharose, 

glucose,  and  levulose,  besides  nitrogenous  substances  partially  peptonised  and 

transformed  into  amino-acids;   also  lactic  acid  and  potassium  phosphates. 

Fermentation  with  yeast  converts  the  carbohydrates  more  or  less  completely 

into  alcohol  and  carbon  dioxide.1 

1  In  addition  to  what  has  been  said  on  pp.  133  and  146  on  ferments  and  yeasts  in  general, 
the  following  is  of  interest,  especially  to  the  brewing  industry  : 

All  yeasts  which  attack  only  saccharose,  maltose,  glucose,  and  levulose,  giving  alcohol  and 
carbon  dioxide,  are  feebly  attenuating  yeasts  of  the  so-called  Saaz  type  (e.  g.,  the  beer-yeasts 
of  Liege,  which  yield  fairly  full-tasting  sweet  beers  containing  little  alcohol).  Other  yeasts 
are  also  capable  of  fermenting  the  combined  maltose  of  maltodextrins  by  means  of  a  special 
enzyme  studied  by  Delbriick,  maltodextrinase ;  these  yeasts  give  the  maximum  attentuation 
and  form  the  so-called  Frohberg  type,  producing  alcoholic,  highly  attentuated  beers  even  from 
weak  worts.  Between  these  types — Saaz  and  Frohberg — there  exist  intermediate  ones  giving 
in  4  days  at  25°  to  27°,  well-defined  attentuations  in  a  normal  wort. 

Certain  other  yeasts  are  capable  of  fermenting  dextrin  combined  as  maltodextrins,  since 
they  contain  an  enzyme  which  Delbriick  has  termed  dextrina^e.  Such  is  the  Schizosaccharomyces 
Pombe,  separated  from  the  millet  beer  of  the  Egyptians.  These  yeasts  constitute  the  so-called 
Logos  type.  Wild  yeasts  are  all  strongly  attenuating  and  may  produce  turbidity  in  finished, 
slightly  fermented  beers,  which  they  referment.  The  yeasts  intermediate  to  the  Saaz  and 
Frohberg  types,  and  also  Frohberg  yeasts  themselves,  are  especially  active  in  the  secondary 
fermentation;  they  increase  the  apparent  fullness  of  the  beer,  even  when  this  is  light,  and 
maintain  a  continuous  and  desirable  evolution  of  carbon  dioxide  by  slowly  fermenting  the  malto- 
dextrins and  even  dextrins.  In  order  to  grow  and  multiply,  yeasts  require,  in  addition  to 
carbohydrates  and  free  oxygen,  nitrogenous  substances,  but  they  cannot  make  use  of  nitrates, 
or  ammonium  salts,  or  even  the  true  proteins;  they  can,  however,  utilise  the  decomposition 
products  of  the  latter,  namely,  the  ammo-acid,1!  (such  as  asparagine)  produced  by  the  proteolytic 
enzymes  secreted  by  healthy  yeasts.  They  require  also  mineral  substances,  e.  g.,  calcium  and 
potassium  phosphates. 

The  oxygen  of  the  air  is,  as  has  been  said,  indispensable  to  the  development  and  multiplication 


FIG.  168. 


FERMENTATION  205 

The  concentration  of  the  wort  most  favourable  to  the  multiplication  of 
yeast  is  15°  Balling  (corresponding  with  a  specific  gravity  of  1'OG).1  A  too 
dilute  wort  or  one  prepared  with  an  excessive  proportion  of  non-germinated 
grain  has  not  sufficient  assimilable  nitrogenous  food  (amino-acids),  and  this 
is  remedied  by  the  addition  of  zymogen,  which  is  a  commercial  product.  During 
the  period  when  the  yeast  develops  (first  stage  of  the  fermentation)  little 
alcohol  and  much  carbon  dioxide  are  produced. 

Two  distinct  methods  of  fermentation  are  in  use  :  top  fermentation,  used 
generally  in  Great  Britain,  Belgium,  and  Holland,  and  largely  in  France,  and 
also,  at  one  time,  exclusively  in  Italy ;  and  bottom  fermentation,  usually  employed 
in  Germany,  Austria,  and  Denmark,  and  in  general  use  in  countries  where 
beers  of  the  Munich  and  Pilsen  types  are  made.  In  hot  countries  it  is  easier 
to  regulate  bottom  fermentation  (by  refrigeration)  than  top  fermentation, 
since  in  summer  the  temperature  of  the  air  is  often  high  enough  to  have  an 
injurious  effect  on  top  fermentation.  Hence,  as  a  refrigerating  plant  is  necessary, 
the  bottom  fermentation  system  is  preferable. 

The  difference  between  bottom  and  top  yeasts  is  that  the  latter  are  covered 
with  viscous,  mucilaginous  substances  and  readily  stick  together  and  carry 
bubbles  of  carbon  dioxide  developed  in  the  wort  to  the  surface  and  so  produce 
a  rapid  fermentation;  the  former,  however,  fall  to  the  bottom  of  the  fer- 
menting vessel,  and  even  under  the  microscope  are  not  found  in  large  masses. 
Top  yeasts  develop  well  only  at  temperatures  above  12° — best  at  about  24° 
— and  effect  complete  fermentation  in  four  to  six  days,  whilst  the  bottom 
yeasts  develop  below  10°  and,  after  the  vigorous  primary  fermentation  at  6° 
to  8°  (eight  to  ten  days  for  Munich  beer,  ten  to  fourteen  for  Vienna  beer,  and 
twelve  to  sixteen  for  Pilsen  beer),  continue  the  maturation  of  the  beer  for  two  or 
three  months  by  a  secondary  fermentation  at  a  low  temperature  (0°  to  2°) ; 
this  procedure  gives  beers  of  less  attenuation  which  can  be  produced  or  con- 
sumed even  in  summer  (lager  beer).  Top-fermentation  beers  are  almost  always 
more  highly  attenuated,  are  consumed  at  once  (draught  beer),  and  are  made 
more  especially  in  the  cold  weather ;  they  can,  however,  be  kept,  and  in  some 
cases  stock  beers  are  made  on  this  system. 

The  advantages  and  disadvantages  of  the  two  processes  are  as  follow  : 
Top  fermentation  does  not  require  costly  refrigerating  plant,  and  hence  lends  itself 
to  the  construction  of  small  breweries;  further,  the  beer  can  be  sold  immediately,  and 
the  capital,  although  small,  thus  frequently  renewed  each  year.  The  control  and  successful 
working  of  top  fermentation  are,  however,  more  difficult,  owing  to  ready  contamination 
with  numerous  harmful  bacteria  which  find  at  15°  to  20°  the  most  favourable  conditions  for 
their  development,  especially  in  the  summer;  in  bottom-fermentation  beers  only  yeasts 
can  develop  at  0°  to  2°. 

With  top  fermentation,  in  which  at  first  yeasts  of  the  Saaz  type  and  those  intermediate 
to  the  Saaz  and  Frohberg  types  predominate,  there  develop  later  bacteria  and  also  Frohberg 
yeasts  (especially  during  the  secondary  fermentation),  and  both  of  these  render  difficult  the 
preparation  of  a  clear  beer  which  does  not  become  turbid  after  fermentation ;  on  the  other 
hand,  a  bright  beer  is  easily  and  naturally  obtained  by  bottom  fermentation.  In  summer 
then,  unless  an  abundant  supply  of  cold  water  and  also  cool  cellars  are  available,  and 
rigorous  precautions  and  disinfection  are  resorted  to,  it  is  very  difficult  to  prepare  top 
fermentation  beer,  whilst  the  low  temperature  required  for  bottom  fermentation  can 
be  attained  at  any  season  of  the  year  by  refrigerating  plant.  Bottom  fermentation  gives 

of  yeast,  and  well-aerated  worts  facilitate  the  multiplication  during  the  first  few  days,  when  only 
C02  and  H20  are  produced;  when,  however,  the  supply  of  free  oxygen  diminishes  or  ceases, 
the  yeast  produces  more  especially  alcohol  and  carbon  dioxide.  •  There  are  also  saccharomyces 
which  are  solely  aerobic  and  form  membranes  on  the  surface  of  the  wort,  producing  only  carbon 
dioxide  and  water  and  destroying  the  alcohol  produced  by  other  yeasts. 

1  The  strengths  of  the  worts  for  beers  of  different  types  are  :  9  to  10°  Balling  for  light  beers ; 
12°  to  13°  for  draught  beers  (Schenkbier);  15°  to  20°  for  double  beers  (Bock  or  Salvator  beer); 
and  up  to  25°  for  table  beers. 


206 


ORGANIC    CHEMISTRY 


beers  of  a  more  constant  type,  since  the  mother-yeast  from  successive  fermentations  does 
not  become  contaminated  so  easily  as,  and  hence  requires  renewal  less  frequently  than,  with 
top  fermentation.1 

When  a  large  amount  of  yeast  is  added  to  a  wort  the  fermentation  is  initiated  and 
completed  more  rapidly;  with  small  quantities  the  same  result  is  obtained,  but  after  a 
longer  time,  so  that  there  is  more  danger  of  contamination.  Usually  250  to  300  grams 
of  pressed  yeast  is  used  per  hectolitre  of  wort — rather  more  for  strong  worts. 

Especially  with  top,  but  also  with  bottom  fermentation,  it  is  most  important  that  all 
instruments,  vessels,  and  rooms  should  be  kept  clean  and  disinfected.  For  this  purpose, 
boiling  water  is  used  and  also  dilute  solutions  of  hydrofluoric  acid,  ammonium  fluoride, 
ammonium  fluosilicate,  calcium  bisulphite,  or  calcium  hypochlorite.  In  all  cases,  however, 
great  care  must  be  taken  to  remove  the  disinfectant  completely  with  abundant  supplies  of 
hot  water,  in  order  that  the  yeast  may  not  be  injured.  Chloride  of  lime  is  eliminated  by 
rinsing  first  with  bisulphite  solution  and  then  with  hot  water.  Even  traces  of  bisulphite 
(sometimes  added  during  mashing  to  prevent  the  action  of  lactic  ferments)  must  be  com- 
pletely eliminated,  otherwise,  during  the  alcoholic  fermentation,  which  is  a  process  of  reduction, 

they  may  yield  hydrogen  sulphide  and 
so  give  a  bad  taste  and  odour  to  the 
beer.  (Bacteria  capable  of  producing 
hydrogen  sulphide  sometimes  develop 
in  beer.) 

The  yield  and  quality  of  the  beer 
may  be  improved  by  adding  a  pure 
culture  of  lactic  acid  bacteria  (prefer- 
ably Bacillus  Delbriicki,  see  p.  152)  at 
the  time  of  pitching  (i.  e.,  addition  of 
the  yeast). 

Whatever  system  of  fermentation 
is  used,  it  is  always  divided  into  two 
phases  :  the  primary  or  vigorous,  and 
the  secondary.  The  primary  fermen- 
tation begins  twelve  or  twenty-four 
hours  after  pitching,  when  the  yeast 
has  grown  to  some  extent  at  the 
expense  of  the  dissolved  oxygen,  and 
continues  for  three  or  four  days  in  the 
case  of  top  fermentation  or  for  ten  to 
twelve  days  with  bottom  fermenta- 
tion ;  considerable  quantities  of  carbon 
FIG.  169.  dioxide  are  developed,  these  forming 

a  dense,  white,  frothy  head  on  which 

may  be  seen  brownish  spots  of  hop  resin  or  agglutinated  bacteria.  In  top  fermentation, 
this  first  head  is  removed,  the  next  darker  one  being  collected  for  pitching  purposes. 

In  the  bottom  fermentation  system,  and  in  large  modern  breweries  in  general,  in  order 
that  the  yeast  may  be  kept  as  pure  as  possible,  the  pitching  is  carried  out  in  the  manner 
described  on  p.  152  for  distilleries. 

1  With  top  fermentation,  the  type  and  taste  of  the  beer  are  determined  by  the  united  activity 
of  a  number  of  different  yeasts  and  bacteria  which  are  present  in  given  equilibrated  proportions, 
these  becoming  modified  as  contamination  increases.  When  the  yeast  is  renewed,  the  pure 
yeast  naturally  gives  a  different  taste  to  the  beer,  and  this  inconvenience  cannot  be  avoided  by 
preparing  a  mixture  of  yeasts  and  bacteria  similar  to  that  normally  present  in  the  partially 
contaminated  top  fermentation.  New  pure  yeasts  are  less  resistant  to  contaminating  sur- 
roundings than  old  ones  are. 

Attempts  are  made  to-day  to  keep  the  fermentation  pure  as  long  as  possible  by  the  use  of 
good  hops,  the  resins  of  which  exert  an  agglutinating  and  paralysing  action  on  the  bacteria,  so 
that  these  can  be  removed  from  the  tun  with  the  first  scum  forming  on  the  surface  of  the 
fermenting  wort ;  the  purer  yeast  of  succeeding  heads  is  then  collected  for  pitching  subsequent 
worts.  When  the  collection  of  the  yeasts  is  delayed,  that  of  the  Frohberg  type  increases.  With 
the  object  of  maintaining  the  cultures  naturally  pure  and  constant,  Effront  has  proposed  the 
addition  of  abidic  acid — a  component  of  lupulin  and  of  colophony — to  agglutinate  and  render 
innocuous  the  bacteria  in  fermenting  worts  (see  also  p.  167).  Thus,  after  elimination  of  the 


ATTENUATION    OF    BEER  207 

During  the  primary  fermentation,  a  considerable  quantity  of  heat  is  evolved,  and  to 
prevent  the  temperature  exceeding  22°  to  25°  in  top  or  7°  to  8°  in  bottom  fermentation, 
attemperating  coils,  through  which  cold  water  (top)  of  brine  (bottom)  passes,  are  used  to 
cool  the  fermenting  wort  (F,  Fig.  169).  Each  fermenting  vat  is  provided  with  a  slate, 
etc.,  on  which  are  noted,  each  day,  the  temperature  and  the  specific  gravity  of  the  wort; 
the  attenuation  should  reach  58  to  62  per  cent,  in  the  primary  fermentation  and  70  to 
75  per  cent,  in  the  secondary  fermentation,  in  order  that  the  beers  may  keep  in  the  warmer 
rooms  of  the  consumers.1  When  the  vigorous  fermentation  is  ended,  the  head  falls  and 
almost  disappears,  carrying  to  the  bottom  of  the  wort  the  suspended  yeast ;  in  this  way 
the  secondary  fermentation  is  started,  this  being  allowed  to  proceed  for  fifteen  to  twenty 
days  in  the  trade  casks  placed  in  cellars  at  10°  to  12°  (for  top  fermentation);  the  beer  is 
then  cleared,  filtered,  and  sold.  In  bottom  fermentation,  on  the  other  hand,  the  secondary 
fermentation  is  completed  in  large  tuns  pitched  inside  (see  later) ;  these  are  not  quite  filled 

bacteria  with  the  first  scums,  purer  yeast  can  be  collected  and  washed  with  pure  water  or,  better/ 
with  water  containing  a  little  hydrofluoric  acid  or  ammonium  fluoride  (5  to  10  grams  per  hecto- 
litre), which  attacks  the  bacteria,  but  not  the  yeast.     It  cannot,  however,  be  denied  that,  in 
general,  washing  produces  considerable  weakening  of  yeast,  which  may  be  reinvigorated  by 
preliminary  growth  in  sterilised,  unhopped  wort. 

1  Determination  of  the  Attenuation  and  of  the  Apparent  and  Real  Extracts  of  Beer.  The 
apparent  extract  is  deduced  from  the  density  of  the  well-shaken  (to  remove  C02)  beer  and  the 
corresponding  number  of  degrees  Balling.  The  real  extract  is  deduced  from  the  specific  gravity 
(and  Balling's  tables)  of  the  beer  freed  from  alcohol  by  evaporating  it  to  one-third  of  its  volume 
and  making  the  residue  up  to  the  original  volume.  The  original  extract  of  the  wort  may  be  calcu- 
lated with  moderate  accuracy  by  adding  to  the  real  extract  the  amount  of  alcohol  (determined 
as  in  wine,  p.  174)  multiplied  by  1-92. 

The  degree  of  real  attenuation  (A)  is  referred  to  1  hectolitre  of  wort  and  indicates  how  many 
parts  per  100  of  the  extract  of  the  wort  are  transformed  into  alcohol  and  carbon  dioxide ;  it  is 
obtained  by  means  of  the  following  formula  : 

A  =  ^JL*  x  100, 

where  D  represents  the  percentage  of  extract  in  the  wort  and  d  the  percentage  of  real  extract  of 
the  beer. 

In  practice,  the  percentage  of  extract  is  sometimes  replaced  by  the  degrees  Balling,  but  the 
results  thus  obtained  are  not  very  exact.  If  we  make  D  =  15°  Balling  and  d  —  5°,  the  real 
attenuation  becomes  : 

ig 5 

A  =  — 15—   X  100  =  66-66  per  cent. 

It  cannot,  however,  be  denied  that  Balling  degrees  refer  to  kilos  of  sugar  or  of  extract  in  100 
kilos  of  solution,  so  that  a  wort  showing  15°  Balling  (sp.  gr.  1-0615)  contains  15  kilos  of  extract 
per  100  kilos  of  wort,  or  15-922  kilos  (i.  e.,  15  X  1-0615)  in  a  hectolitre  of  wort;  the  beer,  free 
from  alcohol,  showing  5°  Balling,  has  a  sp.  gr.  1-020,  and  1  hectolitre  contains  5-100  kilos  of 
extract,  so  that  10-822  kilos  of  extract  has  been  fermented  and  the  true  attenuation  is 

10-822 

15^922  x  10  =  67-6  per  cent. 

Practical  brewers  find  it  more  convenient,  in  considering  the  degree  of  attenuation  of  a  wort, 
to  calculate  the  degree  of  apparent  attenuation  (A')  from  the  apparent  extract  of  the  beer  d  by 

means  of  the  formula,  A'  —  — j^ —  X  100;   for  example,  a  wort  of   16°  Balling  has  the  sp.  gr. 

1-0658  and  1  hectolitre  contains  17-05  kilos  of  extract,  while  the  beer,  with  7°  Balling  of  apparent 
extract,  has  the  sp.  gr.  1-0281,  corresponding  with  7-20  kilos  of  extract  per  hectolitre  The 

17-05 7-20 

apparent  attenuation  is  hence 17.05 —   X  100  =  57-9  per  cent. 

The  attenuation  may  be  deduced  in  a  rather  less  exact  manner  if  instead  of  degrees  Balling 
is  used  degrees  of  the  legal  densimeter  (i.  e.,  the  figures  in  the  second  decimal  place  of  the  specific 
gravity,  a  value  of  1-063  for  the  latter  thus  corresponding  with  6-3°  on  the  legal  densimeter). 
In  the  above  example,  16°  Balling  corresponds  with  sp.  gr.  1-0658,  hence  with  6-58°  on  the  densi- 
meter; similarly,  7°  Balling  corresponds  with  2-81  densimeter  degrees.  Hence  the  apparent 
attenuation  is  given  by  : 

g.gg 2-81 

A'  = g^g X  100  =  57-3  per  cent., 

which  differs  little  from  the  value  calculated  above  from  the  degrees  Balling,  and  is  sufficiently 
exact  for  practical  purposes.  Hence,  both  for  real  and  apparent  attenuation,  Balling's  tables 
may  be  dispensed  with,  it  being  sufficient  to  determine  the  specific  gravity.  It  should  be  noted 
that  the  legal  density  expresses  the  weight  of  wort  contained  in  the  volume  occupied  by  1  kilo 
of  water  measured  at  17-5°. 


208  ORGANIC    CHEMISTRY 

and  are  kept  for  one  to  three  months  in  cellars  maintained  continually  at  0°  to  2°,  where  the 
beer  acquires  the  desired  attentuation  and  its  characteristic  flavour.  The  yeast  which  is 
deposited  in  the  fermenting  vessels  may  be  collected,  pressed  (p.  149)  and  sold  to  bakers 
or  small  brewers. 

In  some  breweries  the  carbon  dioxide  is  now  drawn  off  from  the  fermenting  vats,  which 
are  fitted  with  covers,  by  pumps  and,  after  being  passed  through  potassium  permanganate 
solution  to  purify  it,  the  gas  is  then  liquefied  (see  Vol.  I.,  p.  480) ;  it  may  be  either  utilised 
in  the  brewery  itself  or  sold. 

The  fermenting  vessels  and  the  storage  casks  are  constructed  of  oak  or  pitch-pine. 
The  use  of  glass  vats  has  been  proposed,  as  these  retain  the  pure  flavour  of  the  beer ;  such 
a  vat  to  hold  42  hectolitres  cost  about  £40  before  the  war.  The  inner  walls  of  the  vats  are 
sometimes  coated  with  shellac,  paraffin  wax  or  pitch.  The  cellars  have  walls  and  floor  of 
concrete  (1  metre  higher  than  the  first  aqueous  border  of  the  subsoil)  so  that  they  may  be 
washed  when  necessary ;  the  roof  is  of  brickwork.  These  cellars  are  furnished  with  draughts 
to  remove  the  carbon  dioxide,  with  double  doors  (always  on  the  north  side)  to  prevent  the 
entry  of  warm  air  from  outside  and  with  electric  lighting  so  that  windows,  which  dissipate 
the  cold,  may  be  avoided.  The  vats  and  casks  are  raised  50  to  60  cm.  from  the  ground  and 
are  inclined  slightly  forward  so  that  they  may  be  emptied  completely  and  easily  cleaned 
from  outside.  Along  the  ceiling  run  pipes  for  the  circulation  of  cold  brine  (bottom  fermen- 
tation), which  maintain  a  temperature  below  6°  in  the  fermentation  cellars  and  one  of 
0°  to  2°  in  the  lager  cellars. 

Ten  or  fifteen  days  before  the  beer  is  run  off  from  the  lager  vessels — which  have  been 
several  times  filled  up  to  avoid  contact  of  the  beer  with  the  air  and  consequent  danger 
from  acetic  ferments — the  bung-hole  is  tightly  closed  so  as  to  supersaturate  the  beer  under 
slight  pressure  with  carbon  dioxide,  which  is  still  developed  more  or  less  feebly  according 
to  the  state  of  maturity  of  the  beer.  If  a  beer  contains,  say,  0-15  to  0-25  per  cent,  of 
CO2  before  the  bung-hole  is  closed,  it  will  subsequently  contain  3  to  8  per  cent.,  which 
considerably  enhances  the  keeping  properties. 

Nathan-Bolze  Rapid  Process  (Ger.  Pat.  135,539,  1900).  This  process  was  tested  on 
an  industrial  scale  in  1904  in  the  Fermentation  Institute  at  Berlin,  and  gave  satisfactory 
results.  The  application  of  the  process  has  not,  however,  progressed  as  rapidly  as  was 
hoped  for  a  process  which  allows  of  mature  beer  being  prepared  in  eight  to  ten  days,  and 
works  under  conditions  of  sterilisation  formerly  attainable  only  in  the  laboratory  or  in  the 
manufacture  of  spirit  by  the  Amylo  process  (p.  155).  The  hot,  sterile  wort  from  the 
copper  passes  into  a  large,  hermetically  sealed,  sterile  vessel  of  enamelled  iron  (a  special 
resistant  enamel  being  employed)  surrounded  by  an  iron  jacket  through  which  water  can 
be  passed.  These  vessels  have  a  capacity  of  125  hectolitres  or  more  and  are  called  Hansena 
vessels.  They  are  provided  with  powerful  stirrers  (Fig.  170),  which  keep  the  wort  in  con- 
tinual motion  during  the  fermentation  and  thus  accelerate  the  transformation  of  the 
maltose  into  alcohol  and  carbon  dioxide. 

After  the  temperature  of  the  wort  has  been  lowered  to  50°  by  passing  water  through 
the  jacket  and  the  diminution  of  pressure  (owing  to  the  condensation  of  steam)  compen- 
sated by  the  admission  of  sterilised  air,  the  latter  (which  has  served  also  to  aerate  the 
wort)  is  replaced  by  carbon  dioxide,  the  cooling  being  continued  to  10°.  The  pure  yeast 
is  then  introduced  through  suitable  pipes,  the  mass  being  slightly  stirred  .atr  intervals 
of  an  hour.  The  gas  developed  is  removed  in  order  to  hasten  the  fermentation,  and  is 
washed  with  permanganate,  part  of  it  then  being  compressed  (see  above).  The  carbon 
dioxide  which  is  not  compressed  is  utilised  to  remove  the  new  beer  flavour  from  beer  already 
fermented  in  the  Hansena  vessels;  the  gas  is  passed  in  at  the  bottom  (after  removal  of 
the  yeast  sediment)  at  the  ordinary  temperature,  the  mass  being  continually  stirred  mean- 
while, it  being  the  carbon  dioxide  which  effects  the  elimination  from  the  beer  of  the  volatile 
products  to  which  the  disagreeable  taste  and  odour  of  new  beer  are  due.  The  gas  issues 
from  the  top  of  the  vessel,  passes  to  the  purifiers  and  is  again  conducted  through  the  beer, 
this  process  being  continued  for  ten  hours  on  end.  The  primary  fermentation  is  finished 
is  less  than  three  days,  and,  after  the  passage  of  gas  through  the  beer  is  completed,  the 
temperature  is  lowered  to  0°  and  the  beer  saturated  for  twenty-four  hours  with  slightly 
compressed  carbon  dioxide.  The  beer  is  finally  filtered  and  delivered  to  the  trade  casks, 
where  it  keeps  well  even  in  the  hot  weather. 

Such  a  process,  simple,  rapid,  and  economical  (the  cost  of  the  beer  being  diminished 


209 


by  about  2s.  6d.  per  hectolitre),  although  it  does  not  give  a  very  delicate  flavoured  beer, 
should  be  suitable  to  hot  countries  and  to  small  breweries.  Several  European  breweries 
already  work  on  these  lines,  and  in  1907  one  was  constructed  at  Milan  to  employ 
a  modification  of  the  Nathan  patent,  consisting  of  a  system  intermediate  to  the  old  process 
with  open  fermenting  vessels  and  that  devised  by  Nathan;  in  this  case  enamelled  iron 
vessels  are  used  both  for  the  primary  fermentation  and  for  the  maturation  (three  to  four 
weeks).  These  vessels  cost  about  £1  for  each  hectolitre  of  capacity. 

If  to  the  Nathan  process  is  added  the  Meura  system  of  mashing  (1891) — which  has 
rendered  the  preparation  of  the  wort  as  simple  as  possible  by  mashing  the  finely  ground 
malt  in  a  horizontal  cylinder  fitted  with  stirrers  so  that  the  mash  may  be  rapidly  cooled 
or  heated  and  wort  ready  for 
passing  to  the  filter-press  and 
thence  to  the  copper  obtained 
in  an  hour — it  will  be  under- 
stood how  the  manufacture  of 
ordinary  beer  has  been  shorn  of 
those  practical  and  theoretical 
difficulties  long  regarded  as 
insurmountable. 

RACKING  OF  BEER. 
Beer  is  delivered  to  the  con- 
sumer in  bottles  and  in  casks, 
and  should  be  perfectly  bright, 
cold,  and  supersaturated  with 
carbon  dioxide.  To  render  it 
bright,  the  old  method  of 
clarification  with  gelatine  or  of 
nitration  through  bags  has  now 
been  largely  replaced  by  the 
use  of  the  filter-press,  which 
acts  more  rapidly  and  yields 
brilliant  beer.  The  filtration 
is  carried  out  in  suitable  frames 
through  filter-cloths  or,  better, 
through  finely  divided  cellulose 
(such  as  is  used  in  paper- 
making)  under  a  pressure  of 
about  half  an  atmosphere. 
These  filter-presses  are  the  same 
in  principle  as,  and  little 
different  in  form  from,  those 
which  are  used  for  the  filtration 
of  saccharine  liquids  and  are 
described  in  the  section  on 
Sugar.  (In  England,  beer  in 
cask  is  clarified  by  mixing  with 
the  beer  a  small  quantity  of 

finings,  which  consist  of  isinglass  "  cut "  or  dissolved  in  an  acid,  such  as  tartaric, 
sulphurous,  etc. ;  these  finings  are  gradually  deposited  on  the  bottom  of  the  cask  and 
carry  down  with  them  any  suspended  protein  substances,  hop-resins,  etc.)  Bottling  is 
to-day  carried  out  with  all  the  care  employed  in  the  preparation  of  sparkling  wines. 
A  few  lines  may  be  devoted  to  the  preparation  of  beer-casks,  since  the  methods  employed 
are  peculiar  to  the  brewing  industry. 

In  order  that  beer  for  retail  consumption  may  retain  its  flavour,  it  must  be  kept  cool 
and  saturated  with  carbon  dioxide  up  to  the  moment  when  it  is  drawn  off  into  the  customers' 
glasses,  and  for  this  purpose  the  use  of  liquid  carbon  dioxide  with  the  arrangement  shown 
in  Vol.  I.,  p.  483,  is  well  adapted. 

RESIDING  OR  PITCHING  OF  CASKS.     The  keeping  of  beer  sound  depends  largely 
on  the  cleanliness  of  its  surroundings  and  of  the  vessels  in  which  it  is  stored.     Hence 
VOL.  II.  14 


210 


ORGANIC    CHEMISTRY 


the  casks,  returned  empty  from  the  customers,  are  first  well  scrubbed  and  washed  both 
inside  and  outside  with  water  under  pressure  by  means  of  automatic  plant  (Fig.  171), 
and  are  then  disinfected  by  means  of  formalin  vapour  or  other  antiseptics,  or,  better  still, 
by  pitching  the  internal  surface  with  natural  or  artificial  resins,  which  should  be  transparent 
and  have  a  melting-point  of  about  50° ;  in  this  process,  which  was  first  used  in  Bavaria, 
and  is  nowadays  largely  employed  all  over  the  Continent,  aromatic  resins  are  no  longer 
used,  mixtures  of  colophony  with  other  residues  from  the  distillation  of  turpentine  being 
prepared  by  fusion  and  then  rendered  more  elastic  by  the  addition  of  resin  oil  (10  per 
cent. ).  Use  is  sometimes  made  of  a  fused  mixture  containing  50  parts  of  Burgundy  pitch, 

20  of  stearine,  10  of  Japan  wax,  10  of  paraffin 
wax,  5  of  Venetian  turpentine,  and  5  of  gum 
dammar.  To  free  the  casks  from  the  old  resin 
and  coat  them  again  every  time  they  are 
returned  to  the  brewery,  they  are  heated  inside 
by  means  of  air  supplied  from  a  Boots  blower, 
B  (Fig.  172)  and  heated  by  passing  through 
red-hot  coke,  the  hot  air  being  forced  into  the 
casks  through  the  tubes,  D,  for  five  minutes. 
The  old  pitch  is  discharged  and  the  new  pitch 
(about  200  to  250  grams  per  hectolitre),  fused 
and  heated  to  250°,  introduced  into  the  sterile 
cask.  The  bung-hole  is  then  closed,  the  cask 

rotated  automatically  for  a  few  minutes,  the  excess  of  pitch  poured  out,  and  the  rolling 
of  the  cask  continued  until  it  is  cold.  The  lager- vessels  used  for  the  maturation  of  the 
beer  are  treated  in  a  similar  way. 

PASTEURISATION.  Beer,  more  than  wine,  is  subject  to  numerous  changes  and 
diseases  (turbidity  due  to  inferior  materials,  incomplete  saccharification  or  excess  of 
proteins;  acidity  caused  by  acetic  or  lactic  acid;  stinking  fermentation  produced  by 
various  bacteria,  etc. ),  and  it  is  difficult  to  remedy  these  inconveniences  except  by  improve- 
ment in  the  methods  of  working.  In  order  that  beer  may  remain  unchanged  -when  kept 
for  a  long  time  in  bottle  or  when  sent  to  hot  places,  it  is  advisable  to  pasteurise  it.  The 


FIG.  171. 


FIG.  172. 

bottles  are  tightly  stoppered  and  placed  in  vessels  containing  cold  water,  which  is  then 
gradually  heated  to  a  maximum  of  60°  to  65°,  this  temperature  being  maintained  for  ten 
minutes;  the  vessels  should  be  covered  so  as  to  avoid  danger  from  breakages.  The 
water-bath  is  subsequently  allowed  to  cool  slowly  to  the  ordinary  temperature.  Top- 
fermentation  beers  are  rarely  pasteurised,  as  they  sometimes  acquire  an  unpleasant  flavour 
under  this  treatment ;  bottom-fermentation  beers,  however,  undergo  no  change  and  keep 
good  even  for  ten  years. 

In  large  breweries,  very  efficient  pasteurising  apparatus  is  employed,  the  bottles  being 
moved  automatically  in  suitable  vessels  through  which  the  water  moves  in  the  opposite 
direction. 

Of  the  many  improved  forms  in  use  at  the  present  time,  the  Gasquet  circular  type  is 


COMPOSITION    OF    BEER 


211 


shown  in  Fig.  173.  Here  the  chambers  are  filled  successively  .with  baskets  of  bottles, 
which  are  raised  by  suitable  cranes.  The  water,  at  a  gradually  rising  temperature, 
is  drawn  from  each  chamber  by  means  of  a  tube  communicating  with  a  pump,  heated 
by  a  central  thermo-syphon,  and  then  passed  on  to  the  succeeding  chamber.  A  bell  rings 
every  five  minutes  as  a  signal  for  the  bottles  of  a  cool  chamber  to  be  removed  and  replaced 
by  fresh  ones. 

The  bottles  are  made  of  a  special  glass,  which  diminishes  the  proportion  of  breakages 
to  less  than  1  per  cent. 

ALCOHOL-FREE  BEER.  A  proposal  has  recently  been  made  to  manufacture 
beer  containing  no  alcohol  by  treating  wort  directly  at  0°  with  yeast  which  has  previously 
been  subjected  to  special  treatment  effecting  the  destruction  of  almost  all  the  zymase 
but  not  that  of  the  peptase  and  other  proteolytic  enzymes ;  the  carbohydrates  hence  give 
no  alcohol,  the  proteins  alone  being  decomposed.  These  yeasts  remove  the  flavour  of 
fresh  wort,  the  beer  being  used  before  alcoholic  fermentation  begins  (Ger.  Pat.  180,128). 

COMPOSITION  AND  ANALYSIS  OF  BEER.  The  most  varied  types  of 
beer  are  found  in  different  countries,  and  of  each  type  there  are  usually  the 
two  qualities — pale  and  dark.1  The  density  varies  from  TO  10  to  TO 30,  and 
the  amount  of  alcohol  usually  from  3'5  to  4'5  per  cent,  by  volume,  although 
export  beers  often  contain  5  to  5'5  per  cent,  of  alcohol,  and  certain  special 

1  The  compositions  of  some  of  the  best-known  beers  are  as  follow  : 


Alcohol 

Extract 

Ash 

Beat 
attenuation 

Per  cent. 

Per  c'jnt. 

Per  cent. 

Per  cent. 

by  vol. 

by  vol. 

by  vol. 

by  vol. 

Pale  Berlin  beer         ..... 

3-91 

4-85 

0-14 

60-50 

Berlin  lager  beer        ..... 

4-00 

6-15 

0-20 

54-70 

Export  Bavarian  beer         .... 

4-78 

10-67 

0-29 

45-44 

Munich  Spaten  beer  (  at  Munich) 

3-23 

6-61 

0-28 

48-40 

,,         ,,     (at  Milan)     . 

5-23 

— 

— 

— 

Sal  va  tor  beer    ,                ... 

4-64 

9-08 

0-28 

49-00 

Spaten  table  beer  .... 

7-0 

10-35 

— 

57-40 

Bock     

4-20 

7-10 

— 

54-20 

white  beer     ..... 

3-51 

4-73 

— 

59-58 

Vienna  lager  beer       ..... 

3-62 

6-01 

— 

54-50 

Pilsen  beer        ...... 

3-47 

4-97 

— 

59-00 

North  of  France  beer           .... 

3-20 

4-04 

— 

61-20 

Amsterdam  beer         ..... 

4-30 

7-0 

.  — 

36-40 

Brussels  Iambic           ..... 

6-94 

3-30 

.  — 

78-00 

Belgian  faro       ...... 

4-33 

6-1 

— 

62-80 

Bass's  pale  ale  .          .          . 

6-15 

6-87 

— 

64-00 

Scotch  pale  ale            ..... 

8-50 

10-90 

—  . 

59-9 

Dublin  stout      ...... 

7-23 

6-15 

.  — 

70-64 

London  porter  ...... 

5-40 

6-00 

— 

63-3 

American  beer  ...... 

5-89 

6-45 

— 

63-15 

Milan  beer  :  Pilsen  type      .... 

3-92 

5-43 

0-21 

57-91 

„         ,,      Munich  type   .          .               .     . 

3-50 

|6-58 

0-20 

64-63 

Porretti  beer  (Varese)          .... 

3-98 

[5-66 

0-22 

57-45 

Italia  beer  (made  at  Milan  by  the  modified 

Nathan-Boize  process)     .... 

4-78 

6-00 

0-22 

59-43 

The  real  attenuation  (or  degree  of  fermentation,  see  p.  207)  is  calculated  by  multiplying  the 
percentage  of  alcohol  by  1-92  (=  d'),  and  adding  to  this  product  the  extract  of  the  beer,  d;  this 
gives  the  extract,  D,  contained  in  the  wort  prior  to  fermentation  and  then  the  attenuation  or 

2)  _  ^ 
percentage  of  extract  fermented  =  —  =r-    X  100. 


Some  English  breweries  make  stout  from  a  mixture  of  65  per  cent,  of  pale  malt,  10  per  cent. 
of  black  malt  (for  colour)  ,  10  per  cent,  of  caramelised  malt  and  sometimes  10  per  cent,  of  cane- 
sugar  and  5  per  cent,  of  maize.  This  very  dark  beer  is  attenuated  to  a  relatively  small  extent, 
and  retains  a  full,  sweet  taste,  this  being  partly  due  to  the  almost  entire  absence  of  gypsum 
in,  and  the  small  total  hardness  of,  London  water;  for  these  beers  few  hops  are  used.  Export 
stout  is  made  from  worts  having  gravities  as  high  as  25°  Balling,  whilst  porter  is  lighter  in  char- 
acter. The  pale  beers  of  Berlin  are  made  with  a  good  proportion  (75  per  cent.)  of  malted  wheat. 


212 


ORGANIC    CHEMISTRY 


beers  still  more. .  The  amount  of  extract  also  varies  considerably,  being  as 
much  as  12  per  cent,  for  certain  types  of  beer ;  for  ordinary  beers  it  lies  between 
5  and  6  per  cent.  (1  per  cent,  being  maltose).  The  proportion  of  ash  is  generally 
less  than  0'3  per  cent.  The  amount  of  carbon  dioxide  dissolved  varies  from 
0'15  to  0-40  per  cent. 

The  analysis  of  beer  is  carried  out  in  a  similar  manner  to  that  of  wine,  but  the  carbon 
dioxide  is  eliminated  by  heating  the  beer  to  40°  and  shaking  for  several  minutes  before 
the  specific  gravity  and  acidity  are  determined;  the  latter  does  not  exceed  0-3  per  cent, 
and  is  expressed  as  lactic  acid  (1  c.c.  N/10-alkali  =  0-009  gram  lactic  acid)  or  as  cubic 
centimetres  of  normal  alkali  used  per  100  c.c.  of  beer.  To  avoid  frothing  during  the 
distillation  of  the  alcohol,1  a  little  tannin  is  added.  The  nitrogenous  substances  are  deter- 
mined on  the  extract  of  40  c.c.  of  the  beer  by  Kjeldahl's  method  (p.  11 ),  the  proportion  of 


FIG.  173. 

nitrogen  being  multiplied  by  6-25  to  give  the  corresponding  amount  of  proteins.  The 
reducing  sugar  is  determined  by  means  of  Fehling's  solution  and  is  calculated  as  maltose 
(see  Note,  p.  199). 

Beers  are  often  tested  for  added  salicylic  acid,  fluorides,  sulphurous  acid,  etc.  (see 
Villavecchia's  "  Applied  Analytical  Chemistry,"  Vol.  II.,  p.  164). 

STATISTICS.  In  Italy  the  brewing  industry  has  never  been  in  a  flourishing  condition, 
owing  to  the  abundance  and  cheapness  of  wine — possibly  more  commonly  drunk  than 
water.  The  beer  manufactured  from  remote  epochs  in  Italy. was  made  by  the  top-fermen- 
tation process  and  was  of  poor  quality ;  it  did  not  keep  well  in  summer,  was  stored  care- 
lessly by  the  retailers,  and  was  consumed  for  only  about  a  couple  of  months  in  the  year — 
close  to  where  it  was  produced.  Technical  improvements  have  been  introduced  tardily, 
but  nowadays  the  industry  is  largely  concentrated  into  a  few  large  breweries  using  the 
most  modern  methods  and  controlled  by  technical  experts  from  other  countries.  In  1911 
eighty-six  breweries  were  working  in  Italy. 

About  one-half  of  the  beer  imported  into  Italy  is  supplied  by  Austria -Hungary,  about 
one-third  by  Germany,  and  one-tenth  by  Switzerland  : 

1  The  proportion  of  alcohol  may  be  calculated  indirectly  by  means  of  the  formula, 
A  =  (s/S)  ~  S,  where  A  indicates  the  percentage  of  alcohol,  s  the  specific  gravity  of  the  beer, 
S  the  specific  gravity  of  the  beer  freed  from  alcohol  and  made  up  to  the  original  volume;  the 
alcohol  Table  (p.  175)  gives  the  percentage  by  weight  corresponding  with  the  value  of  8/8  and 
division  of  this  percentage  by  8  gives  the  true  percentage  of  alcohol. 


BEER    STATISTICS 


213 


PRODUCTION,  IMPORTATION,  AND  CONSUMPTION  OF  BEER  IN 

ITALY 

Consumption 


1880 
1890 

1894-5  . 
1900 
1903 
1904 

1905-6  . 
1906-7  . 
1907-8  . 
1908-9  . 
1909-10  . 
1910-11  . 
1911-12  . 
1912-13  . 
1913-14  . 
1914-15  . 


Production 
hectols. 

116,000 
160,900 
95,500 
154,000 
185,000 
220,000 
304,000 
360,000 
400,000 
473,000 
563,000  • 
598,000 
721,000 
673,000 
652,300 
526,000 


Imports 
hectols.  in  cask. 

46,900 
99,500 
60,000 
54,750 
70,000 
80,000 
90,000 
94,494 
95,213 
88,100 
89,737 
83,365 
97,700 
90,000 
66,000 
12,000 


Total 

Per  head 

hectols. 

litres. 

163,000 

0-57 

260,000 

0-86 

156,000 

0-50 

209,000 

0-66 

255,000 

0-79 

300,000 

0-92 

394,000 

1-20 

455,000 

1-50 

495,000 

1-60 

561,000 

1-80 

651,000 

2-00 

680,000 

2-10 

815,000 

2-40 

763,000 

2-30 

718,000 

2-20 

538,000 

1-70 

The  consumption  of  beer  in  Italy  takes  place  mostly  in  the  towns  of  the  north  and 
centre,  and  the  average  consumption  per  head  in  Milan,  Turin,  or  Rome  is  at  least  ten 
times  that  for  the  whole  country. 

The  production  and  consumption  of  beer  in  different  countries  are  as  follows  (thousands 
of  hectolitres) : 


1881 

1900 

1905 

1908 

1910 

1913 

Mean  con- 
sumption per 
head  (litres) 

Germany  . 

35,000 

67,000 

66,000 

69,500 

64,000 

68,000 

/118  (1909) 
UOl  (1910) 

Austria-  Hungary 

12,000 

20,000 

— 

20,400 

19,000 

25,000 

80      „ 

Great  Britain     . 

45,000 

59,000 

— 

59,000 

58,000 

60,667 

153      „ 

Belgium     . 

9,000 

14,000 

— 

14,000 

16,000 

16,000 

211      „ 

France 

8,000 

9,000 

13,700 

— 

14,000 

16,000 

32      „ 

United  States     . 

19,000 

48,000 

— 

64,000 

70,000 

73,000 

63      „ 

Russia 

7,000 

— 

6,500 

— 

6,200 

11,500 

5      „ 

Spain 

— 

1,000 

— 

— 

— 

400 

— 

Switzerland 

1,000 

•  — 

— 

— 

1,500 

3,000 

— 

Holland 

— 

— 

— 

— 

— 

1,800 

38      „ 

Norway 

— 

— 

— 

— 

— 

500 

31      „ 

Sweden 

— 

— 

— 

— 

— 

2,850 

56      „ 

Denmark  . 

— 

— 

— 

— 

— 

350 

104      „ 

Japan 

— 

— 

— 

294 

280 

354 

— 

New  Zealand 

— 

— 

— 

— 

2,456 

— 

— 

Argentine,  Chili,  Brazil 

— 

— 

— 

— 

2,241 

1,100 

— 

Whole  world 

— 

— 

— 

— 

271,000 

275,000 

— 

In  Northern  Germany  the  mean  annual  consumption  per  head  was  only  98  litres, 
whereas  in  the  Grand  Duchy  of  Baden  it  amounted  to  158  litres ;  for  Lille  the  quantity 
was  360  litres. 

Delbriick  calculated  that  in  1911  almost  £160,000,000  was  invested  in  breweries  through- 
out the  world,  barley  to  the  value  of  £14,400,000  and  hops  to  the  value  of  £1,600,000  being 
used  in  the  brewing  of  beer. 

In  1900  the  breweries  in  Germany  numbered  10,000.  In  1909  Bavaria  produced 
18,000,000  hectolitres  of  beer,  Wurtemberg  5,500,000,  Baden  3,000,000,  and  North  Germany 
38,000,000. 


214  ORGANIC    CHEMISTRY 

In  1911  the  Schultheiss  Brewery  of  Berlin  made  1,500,000  hectolitres  of  beer  and  the 
Dreher  Brewery  of  Schwechat  (Vienna)  1,100,000  hectolitres. 

A  large  brewery  near  New  York  produces  annually  900,000  barrels  of  beer,  its  ice 
machines  having  a  daily  capacity  of  1600  tons. 

The  brewery  of  Guinness  &  Co.,  Dublin,  makes  about  3,500,000  hectolitres  of  stout 
per  year. 

In  Italy  the  brewing  tax  was  5£d.  up  to  1891,  when  it  was  raised  to  ll|d.  (causing  a 
temporary  diminution  in  the  consumption  at  that  time)  per  saccharometer  degree  per 
hectolitre,  measured  with  the  decimal  saccharometer  at  17-5°  on  the  wort  from  the  cooler, 
an  allowance  of  12  per  cent,  being  made  for  loss  during  the  subsequent  operations;  the 
tax  varied  from  a  minimum  of  9s.  6d.  to  a  maximum  of  15s.  4d.  per  hectolitre,  according  to 
the  strength  of  the  beer.  Imported  beer  pays  2s.  5d.  more,  or  the  importers  can  demand 
the  tax  to  be  levied  on  the  extract  degrees,  these  being  increased  by  twice  the  number 
of  alcohol  degrees.  On  exported  beer  the  duty  is  refunded  to  the  extent  of  9s.  6d.  per 
hectolitre.  The  exchequer  collected  £180,000  in  1905-1906,  £211,800  in  1906-1907,  and 
£320,000  in  1910-1911  as  tax  of  manufacture.  During  the  war  the  duty  was  raised  to 
Is.  5d.  per  hectolitre-degree,  and  it  is  proposed  to  increase  it  to  2s.  5d.  in  1920. 

In  Germany  beer  costs  about  12s.  per  hectolitre,  or  rather  more  with  the  extra  taxation 
of  1910.  In  Italy  the  cost  is  about  32s.  (that  imported  from  well-known  breweries  about 
40s.  per  hectolitre). 

VARIOUS    DERIVATIVES    OF   ETHYL   ALCOHOL 

SODIUM  ETHOXIDE,  C2H5-ONa,  may  be  obtained  by  dissolving  metallic  sodium  in 
absolute  alcohol :  C2H5-OH  +  Na  =  C2H5-ONa  +  H;  when  the  dense  mass  is  cooled,  the 
crystallised  ethoxide  separates  with  3C2H5-OH,  which  it  loses  only  when  heated  to  200°  in  a 
current  of  hydrogen,  a  soft  white  powder  remaining.  The  latter  separates  directly  when 
the  calculated  quantity  of  sodium  is  dissolved  in  absolute  alcohol  previously  dissolved  in 
ether  or  toluene  and  heated  in  a  reflux  apparatus.  The  ethoxide  is  also  obtained  when 
sodium  hydroxide  is  dissolved  in  concentrated  alcohol.  With  excess  of  water  sodium 
ethoxide  decomposes  into  alcohol  and  caustic  soda. 

The  ethoxide  is  largely  used  in  organic  syntheses  and  to  remove  water  and  alcohol; 
before  the  war  it  cost  28s.  to  32s.  per  kilo. 

CALCIUM  ETHOXIDE  (C2H5O)2Ca,  is  formed  on  dissolving  metallic  calcium  in 
alcohol  or  by  heating  calcium  carbide  with  absolute  alcohol. 

ALCOHOLS    HIGHER  THAN   ETHYL  ALCOHOL 

PROPYL  ALCOHOLS,  C3H8O.  The  two  isomerides  theoretically  possible  are  known  : 
(1)  Normal,  CH3  •  CH2  •  CH2  •  OH  (propanol-1  or  ethylcarbinol).  This  may  be  obtained 
from  fusel  oil  (p.  165)  by  fractional  distillation,  or  from  its  bro mo-derivative,  or  by  the 
action  of  magnesium  ethyl  chloride  on  trioxymethylene.  It  has  an  agreeable  odour, 
b.-pt.  97°,  sp.  gr.  0-804,  and  is  readily  soluble  in  water,  but  insoluble  in  cold  saturated  calcium 
chloride  solution  (unlike  ethyl  alcohol).  On  oxidation  it  gives  propionic  acid,  which 
proves  its  constitution. 

(2)  Sec.  Iso-Propyl  Alcohol,  CH3  •  CH(OH)  •  CH3  (propanol-2  or  dimethykarbinol), 
is  a  colourless  liquid,  b.-pt.  81°,  sp.  gr.  0-789.  It  is  obtained  from  isopropyl  iodide  and 
hence  indirectly  from  glycerol,  or  by  reducing  acetone  with  sodium  amalgam,  the  constitution 
attributed  to  it  being  thereby  confirmed. 

BUTYL  ALCOHOLS,  C4H10O.     The  four  isomerides,  predicted  by  theory,  are  known  : 

(1)  Normal  Butyl  Alcohol,  CH3  •  CH2  •  CH2  •  CH2  •  OH  (butanol-l  or  propylcarbinol), 
is  a  liquid,  b.-pt.  117°,  sp.  gr.  0-810,  and  has  an  irritating  odour ;  12  vols.  of  water  at  22°  dis- 
solve only  1  vol.  of  it,  this  being  separated  from  the  solution  by  the  addition  of  a  soluble 
salt.     It  is  found  in  fusel  oil  and  may  be  obtained  by  fermenting  glycerol  or  mannitol  (yield 
8  to  10  per  cent.)  with  Bacillus  butylicus  (contained  in  the  excreta  of  cows).     It  may  also 
be  prepared  synthetically  by  the  various  general  processes  (p.  125).     Its  constitution  is 
indicated  by  its  syntheses  and  by  the  possibility  of  transforming  it  into  normal  butyric 
acid  by  oxidation. 

(2)  Secondary  Butyl  Alcohol,  CH3  •  CH2  •  CH(OH)  •  CH3  (butanol-2  or  ethylmethyl- 
carbinol),  is  a  liquid  with  an  intense,  peculiar  odour,  b.-pt.  100°,  sp.  gr.  0-808.     It  may  be 


HIGHER    ALCOHOLS  215 

obtained  by  treating  the  tetrahydric  alcohol,  erythritol,  C4H6(OH)4,  with  hydriodic  acid 
or  by  the  interaction  of  normal  butylene  and  hydriodic  acid  and  hydrolysis  of  the  resulting 
iodide. 

CH 

(3)  Isobutyl  Alcohol,   ~3;>CH  •  CH2  •  OH  (methylpropanol),  is  termed   also    butyl 

alcohol  of  fermentation,  since  it  abounds  in  the  fusel  oil  of  potatoes,  from  which  it  may  be 
extracted  by  forming  the  corresponding  iodo-compound.  It  is  a  colourless  liquid,  b.-pt. 
107°,  sp.  gr.  0-806,  and  has  a  characteristic  alcoholic  smell.  Its  constitution  is  deter- 
mined by  the  fact  that,  on  oxidation,  it  yields  isobutyric  acid,  the  constitution  of  which 
is  known. 

PTT 

(4)  Tertiary  Butyl  Alcohol,  ,3>C(OH)-CH3  (trimethylcarbinol or  methyl-2-propanol), 

3 

occurs  in  small  proportion  in  fusel  oil,  and  may  be  prepared  by  the  action  of  hot  75  per  cent, 
sulphuric  acid  on  isobutylene,  which  thus  takes  up  1  mol.  of  water.  When  pure,  it  forms 
rhombic  prisms  or  plates,  m.-pt.  25-5°,  sp.  gr.  0-786  (solid),  b.-pt.  83°.  On  oxidation  it 
gives  acetic  acid,  acetone,  and  carbon  dioxide. 

AMYL  ALCOHOLS,  C5Hn .  OH.  The  eight  isomerides  theoretically  possible  are 
known,  the  most  important  being  : 

(1)  Normal  Amyl  Alcohol,  CH3  •  CH2  •  CH2  •  CH2  •  CH2  •  OH  (pentanol-1),  b.-pt.  138°, 
sp.  gr.  0-817,  is  of  little  importance,  and  is  obtained  by  reducing  normal  valeraldehyde  or 
by  the  other  general  methods. 

CH 

(2)  Amyl  Alcohol  of  Fermentation,  ^H3>CH  •  CH2  •  CH2  •  OH  (methyl-3-butanol-l 

or  isobutylcarbinol),  is  a  liquid,  b.-pt.  131°,  sp.  gr.  0-810,  and  is  solid  at  —  134°.  It  dissolves 
in  50  vols.  of  water  at  13-5°,  but  in  presence  of  a  little  ethyl  alcohol  its  solubility  is  greatly 
increased.  It  has  a  higher  bactericidal  action  than  other  alcohols,  and,  owing  to  its  toxicity, 
great  precautions  are  taken  in  its  manufacture  to  protect  the  health  of  the  workpeople ; 
if  it  could  be  obtained  at  a  low  price,  it  might  be  used  for  making  isoprene  and  hence 
synthetic  rubber.  It  imparts  its  characteristic  smell  and  burning  taste  to  fusel  oil,  in 
which  it  abounds.  It  is  to  this  alcohol  that  the  poisoning  effect  of  spirits  is  principally  due. 
It  occurs  naturally  in  Roman  chamomile  oil  and  is  obtained  industrially  from  fusel  oil 
(see  note,  p.  165).  It  is  used  in  large  quantities  to  prepare  amyl  acetate,  which  serves  as 
an  excellent  solvent  for  cellulose  acetate.  Prior  to  the  war  it  cost  £80  to  £120  per  ton. 

In  1911  the  United  States  produced  250  tons.  Germany  exported  82  tons  in  1910, 
56  in  1911,  and  124  in  1912,  and  imported  2-7  tons  in  1910,  36  in  1911,  and  197  in  1912. 

c  TT 

(3)  Active  Amyl  Alcohol,  ;2    5>CH  •  CH2  •  OH  (methyl-2-butanol-l  or  2-methylbutan- 

LJ13 

l-ol),  boils  at  128°,  has  the  sp.  gr.  0-816,  and  is  found  with  the  amyl  alcohol  of  fermentation. 
It  contains  an  asymmetric  carbon  atom  (see  p.  19)  and  is  Isevo -rotatory,  whilst  the  halogen 
compounds  and  the  valeric  acid  derived  from  it  are  dextro-rotatory;  also  the  dextro- 
isomeride  of  this  acid  yields  a  Isevo -rotatory  iodide. 

pTT 

(4)  Tertiary  Amyl  Alcohol,  r,w3^>C(OH)  •  CH2  •  CH3  (methyl-2-butanol-2  or  amylene 

Utl3 

hydrate  or  dimethylethylcarbinol)  is  an  oily  liquid  with  a  faint  odour  of  mint.  It  boils  at 
102°  and  is  prepared  from  amylene  ^>y  the  indirect  addition  of  water  under  the  influence  of 
sulphuric  acid.  It  exerts  a  soporific  effect. 

HIGHER  ALCOHOLS.  Of  these  may  be  mentioned :  Primary  normal  hexyl  alcohol 
or  hexanol,  CH3  •  [CH2]4  •  CH2  •  OH  (14  of  the  18  hexyl  alcohols  predicted  by  theory  are 
known),  which  may  be  obtained  from  caproic  acid,  C6H]2O2,  and  is  found  as  butyric  and 
acetic  esters  in  the  ethereal  oil  of  the  seeds  of  Heracleum  giganteum  and  in  the  fruit  of  Hera- 
cleum  spondylium  :  it  boils  at  158°  (under  740  mm.  pressure),  and  has  the  specific  gravity 
0-820.  Caproyl  or  isohexyl  alcohol,  (CH3)2  :  CH  •  CH2  •  CH2  •  CH2  •  OH,  b.-pt.  150°,  is 
found  in  vinasse  and  in  fusel  oil.  Heptyl  (or  wnanthyl)  alcohol,  C7H160;  of  the  38  possible 
isomerides,  13  are  known.  Normal  octyl  alcoJwl,  C8H18O,  is  contained  in  Heracleum  spon- 
dylium and  Heracleum  giganteum ;  secondary  octyl  alcohol  (or  capryl  alcohol  or  methylhexyl- 
carbinol)  is  formed  on  distilling  castor-oil.  Other  higher  alcohols  are  obtained  by  reducing 
the  corresponding  aldehydes  with  zinc  dust  and  acetic  acid ;  they  are  solid,  like  paraffin 
wax.  Cetyl  or  normal  hexadecyl  alcohol,  Cj^H^O,  combined  with  palmitic  acid,  forms  the 
principal  component  of  sperm  oil.  Ceryl  alcohol  (cerotin),  C26H5.j  •  OH,  occurs  as  cerotic 


216  ORGANIC    CHEMISTRY 

ester  in  Chinese  wax  and  in  wool-fat ;  it  melts  at  76°  to  79°.  Melissyl  or  myricyl  alcohol, 
C30H61  •  OH  ( ? ),  is  found  as  the  palmitic  ester  in  beeswax  and  carnauba  wax,  and  is  obtained 
free  by  saponification  with  alcoholic  potash. 

II.  UNSATURATED   MONOHYDRIC   ALCOHOLS 

These  are  similar  to  the  saturated  alcohols,  but,  as  they  contain  one  or  two  double 
linkings,  they  behave  like  the  olefines  and  diolefines  in  taking  up  two  or  four  atoms  of 
hydrogen,  halogens,  etc.,  to  give  saturated  compounds.  If  they  contain  a  triple  linking, 
— C  =  CH,  they  form  explosive  metallic  compounds,  as  does  acetylene  (p.  110). 

VINYL  ALCOHOL,  CH2  :  CH  .  OH  (Ethenol),  appears  to  be  present  in  commercial 
ether,  but  it  has  never  been  isolated,  attempts  to  synthesise  it  leading,  as  is  the  case  with 
other  similar  compounds,  to  an  isomeride — acetaldehyde,  CH3  •  CHO ;  the  formation  of 
the  latter  is  explained  by  the  addition  of  a  molecule  of  water  to  the  alcohol,  and  immediate 
loss  of  a  molecule  of  water  from  the  compound  thus  formed. 

ALLYL  ALCOHOL,  CH2  :  CH  •  CH2  •  OH  (Propenol),  is  a  liquid  of  pungent  odour, 
density  0-8573  at  15°,  b.-pt.  98°,  and  readily  soluble  in  water.  It  is  formed  in  small  quantity 
in  the  distillation  of  wood  (crude  methyl  alcohol  contains  0-2  per  cent.,  and  the  final  products 
of  the  rectification,  distilling  at  80°  to  100°,  50  per  cent,  of  it).  Industrially  it  is  obtained 
by  heating  glycerol  (4  parts)  with  crystallised  oxalic  acid  (1  part)  or  formic  acid  and 
0-3  per  cent,  of  ammonium  chloride;  below  130°  CO2  is  evolved  with  formation  of  glycerol 
formic  ester,  CH2(OH)  •  CH(OH)  •  CH2  •  COOH,  which  begins  to  decompose  at  205°  to 
210°  and  is  completely  decomposed  at  260°,  with  evolution  of  CO2  and  H2O.  The  crude 
allyl  alcohol  is  distilled  off  (at  195°  to  200°)  and  is  redistilled  until  oil  no  longer  separates, 
when  a  small  portion  of  the  distillate  is  treated  with  potash.  From  the  distillate  the  allyl 
alcohol  is  obtained  as  an  oil  by  addition  of  potash,  the  oil  being  decanted  off,  dried  by 
prolonged  contact  with  lump  caustic  potash,  again  distilled  and  dried  over  potassium 
carbonate  which  has  been  recently  heated  and  then  over  baryta.  The  yield  is  22  to  25  per 
cent,  of  the  weight  of  oxalic  acid  taken. 

Cl,  Br,  CN,  and  HC10  can  be  added  on  to  it  directly,  but  not  H.  When  cautiously 
oxidised,  it  takes  up  0  and  H2O,  giving  glycerol  or  even  acrolem  (allyl  aldehyde)  and 
acrylic  acid,  which  shows  it  to  be  a  primary  alcohol. 

It  is  used  to  prepare  allyl  bromide  and  iodide  (see  below),  esters  of  salicylic  and  cinnamic 
acids,  etc.  The  price  of  the  alcohol  is  28s.  to  32s.  per  kilo,  the  chemically  pure  product 
costing  twice  as  much. 

Derivatives  of  allyl  alcohol  occur  in  the  vegetable  kingdom.  Thus  oil  of  garlic  contains 
diallyl  disulphide  and  triallyl  trisulphide,  and  mustard  oil,  allyl  thiocyanate  (or  allylthio- 
carbimide),  C3H5  •  N :  C :  S.  Mustard  oil  is  obtained  from  pressed  mustard  oil  seeds 
(which  contain  it  as  the  glucoside  of  potassium  myronate,  this  being  easily  decomposed 
by  the  enzyme  myrosin),  and  is  also  prepared  artificially  by  distilling  allyl  iodide  with 
potassium  thiocyanate.  The  natural  product  (containing  94  per  cent,  of  allyl  isothio- 
cyanate)  cost  before  the  war  £2  per  kilo  and  the  artificial  oil  12s.  per  kilo.  It  is  used  for 
preparing  mustard  compounds  and  serves  as  a  vesicatory,  etc. 

CITRONELLOL,  C10H20O,  is  found  in  attar  of  rc^es. 

PROPARGYL  ALCOHOL,  CH  |  C  •  CH2  •  OH  (Propinol),  is  a  liquid  with  a 
pleasant  odour,  lighter  than  water,  b.-pt.  114°. 

GERANIOL,  C10H18O  or  (CH3)2  :  C  :  CH  •  CH2  •  CH2  •  C(CH3)  :  CH  •  CH2  •  OH,  is  a 
pleasant-smelling  oil,  b.-pt.  121°  under  17  mm.  pressure.  It  is  obtained  from  geranium  oil, 
and  on  oxidation  gives  citral  (the  corresponding  aldehyde)  which  occurs  in  mandarin  oil 
and  in  essences  of  orange  and  lemon  and  to  a  very  considerable  extent  (60  per  cent. )  in 
verbena  oil. 

III.  POLYHYDRIC   ALCOHOLS 
(a)  DIHYDRIC   ALCOHOLS   OR   GLYCOLS,  CnH2n(OH)2 

Substitution  of  two  hydrogen  atoms,  joined  to  different  carbon  atoms, 
by  two  hydroxyl  groups  gives  dihydric  alcohols,  containing  two  alcoholic 
groups.  It  is  not,  however,  possible  to  have  two  hydroxyl  groups  united  to 
the  same  carbon  atom — although  similar  compounds  are  known  for  the  ether 


POLYHYDRIC    ALCOHOLS  217 

derivatives  known  as  Acetals  (see  later)— since  even  if  they  could  be  formed 
they  would  immediately  lose  a  molecule  of  water,  forming  aldehydes  or 
ketones. 

The  dihydric  alcohols,  owing  to  their  sweet  taste,  were  called  Glycols  by 
Wurtz,  who  prepared  them  by  transforming  a  dihalogenated  hydrocarbon  into 
the  corresponding  diacetyl-ester  by  means  of  silver  acetate  and  then  saponi- 
fying the  diacetyl  compound  either  by  baryta  or  sodium  hydroxide  or  by 
boiling  with  water  and  lead  oxide  or  sodium  carbonate  solution  : 

CH2Br  CH2-0'COCH3 

+  2CH3  •  COOAg  =  2AgBr  +  | 
CH2Br  CH2  •  0  •  COCH3 

Ethylene  bromide  Diacetylglycol 

CH2  •  0  •  COCH3  CH2  •  OH 

+  2KOH  =  2CH3  •  COOK  +  |  (glycol) 

CH2  •  0  •  COCH3  CH2  •  OH 

A  special  group  of  glycols,  the  pinacones,  containing  two  adjacent  tertiary 
alcohol  groups  (=C  '  OH),  are  formed  by  reducing  the  ketones  with  sodium 
and  water,  or,  better,  together  with  isopropyl  alcohol,  by  electrolysing  a 
dilute  solution  of  sulphuric  acid  and  acetone,  the  latter  being  reduced  at  the 
negative  pole  : 

CH3  •  C(OH)  •  CH3 

3CH3  •  CO  •  CH3  +  H4  =  CH3  •  CH(OH)  •  CH3  +  ; 

CH3  •  C(OH)  •  CH3 

this  pinacone  (2  :  3-dimethyl-2  :  3-butandiol),  melts  at  38°,  boils  at  172°  and 
crystallises  with  6H2O.  When  distilled  with  dilute  sulphuric  acid,  it  is  trans- 
formed into  pinacoline,  (CH3)3C  *  CO  '  CH3,  with  separation  of  H2O  and 
transposition  of  an  alkyl  group. 

The  glycols  have  an  almost  oily  appearance ;  their  solubility  and  sweetness 
increase  with  the  molecular  weight,  while  the  specific  gravity  and  boiling-point 
are  much  higher  than  those  of  the  monohydric  alcohols  with  equal  numbers  of 
carbon  atoms.  The  hydroxyl  groups  of  the  glycols  behave  like  those  of  mono- 
hydric alcohols,  so  that  the  glycols  can  give  rise  to  ethers  and  esters,  alkoxides 
(sodium,  etc.),  halogen  compounds  (e.  g.,  the  chlorohydrins),  aldehydes  and 
acids,  besides  which  they  may  give  up  1  mol.  of  H2O  forming  anhydrides. 

ETHYLENE  GLYCOL  (Ethan- 1  :  2-diol),  C2H4(OH)2,  is  a  dense  liquid,  b.-pt.  198°, 
and,  on  oxidation,  yields  glycollic  acid,  CO2H  •  CH2  •  OH  and  oxalic  acid,  CO2H  •  CO2H. 

PROPYLENE  GLYCOLS.  Two  isomerides  are  known:  a-Propylene  Glycol, 
OH  •  CH2  •  CH(OH)  •  CH3  (propan-1  :  2-diol),  boils  at  188°  and  is  formed  on  distillation 
of  glycerol  with  sodium  hydroxide.  It  contains  an  asymmetric  carbon  atom  and,  by  ths 
action  of  certain  ferments,  the  Isevo -rotatory  isomeride  may  be  isolated.  /3-Propylene 
Glycol  boils  at  216°  and  is  formed  by  the  bacterial  decomposition  of  glycerol,  as  well  as 
by  the  usual  synthetical  methods. 

In  the  higher  glycols,  when  the  two  hydroxyl  groups  have  four  carbon  atoms  between 
them  (y-glycols),  water  is  readily  separated  and  furan  derivatives,  analogous  with  pyrrole 
and  thiophene  compounds,  formed. 

(b)  TRIHYDRIC   ALCOHOLS,    CHH2M_1(OH)3 

These  are  colourless,  dense  liquids  with  a  sweetish  taste  and  readily  soluble 
in  water ;  they  contain  at  least  three  carbon  atoms  and  three  hydroxyl  groups, 
and  are  hence  capable  of  forming  three  series  of  esters  by  combination  with  a 
monobasic  acid. 

GLYCEROL  (or  Glycerine),  C3H5(OH)3,  or  OH  'CH2  -CH(OH)  'CH2  •  OH 
(Propantriol),  was  discovered  by  Scheele  in  1779.  Chevreul  and  Braconnot 


218  ORGANIC    CHEMISTRY 

(1817)  found  it  as  a  component  of  all  oils  and  fats.  Its  formula  and  con- 
stitution were  established  later  (Pelouze,  Wurtz,  and  Berthelot).  It  occurs 
abundantly  in  nature,  not  in  the  free  state,  but  combined  with  higher  fatty 
acids  in  the  form  of  esters  (glycerides),  which  form  the  fats  and  oils;  these 
contain  9  to  11  per  cent,  of  combined  glycerol. 

It  exists  free  in  rancid  fats  and  is  formed  in  small  proportions  in  the  fer- 
mentation of  sugar  (all  wines  contain  0*98  to  T67  per  cent.). 

During  the  European  War  glycerol  was  prepared  in  Germany  to  some  extent 
by  biological  processes  and  was  sold  in  the  pure  state  under  the  name  of  protol.1 
Industrially  glycerol  is  obtained  principally  from  factories  where  fats  are 
decomposed  (stearine-  and  soap-works).  Synthetically  it  may  be  obtained  by 
transforming  propylene  (from  isopropyl  iodide),  by  means  of  chlorine  in  the 
hot,  into  dichloropropane,  C3H6C12,  which,  with  iodine  chloride,  gives  the 
trichloro-derivative,  C3H5C13;  the  latter,  when  heated  with  water  at  170°, 
gives  glycerol : 

CH2C1  •  CHC1  •  CH2C1  +  3H2O  =  3HC1  +  OH  •  CH2  •  CH(OH)  •  CH2  •  OH. 

This  formation  of  glycerol  and  also  that  by  the  oxidation  of  allyl  alcohol, 
CH2  '  CH  •  CH2  *  OH,  demonstrate  the  constitution  of  glycerol.  On  the  other 
hand,  it  is  possible  to  prepare  glycerol  synthetically  from  the  elements  by  way 
of  acetylene,  acetaldehyde  (p.  110),  acetic  acid,  acetone  (by  distillation  of 
calcium  acetate),  isopropyl  alcohol  (by  reduction),  propylene,  and  thence,  as 
above,  to  glycerol  (Friedel  and  Silva). 

PROPERTIES.  Glycerol  (also  termed  glycerine)  is  an  oily,  colourless,  dense 
liquid  of  sp.  gr.  T2641  at  15°,  and  1-26413  +  (15  —  t)  0'000632  at  any  other 
temperature,  t.  It  is  highly  hygroscopic  when  concentrated,  but  this  property 
is  no  longer  shown  when  the  glycerol  contains  20  per  cent,  of  water.  It  dis- 
solves in  water  and  in  alcohol  in  all  proportions,  heat  being  generated  when 
58  parts  of  glycerol  are  mixed  with  42  parts  of  water.  Glycerol  has  a  sweet 
taste. 

It  is  insoluble  in  ether  or  chloroform;  it  dissolves  to  the  extent  of  5  per 
cent,  in  drji  acetone  and  to  a  greater  degree  in  aqueous  acetone.  It  boils  at 
290°  with  partial  decomposition,  but  it  may  be  distilled  unchanged  in  a  vacuum 
(at  10  mm.  pressure  it  boils  at  162°).  It  crystallises  at  —  40°  or  at  a  higher 
temperature  if  it  contains  water ;  the  separated  crystals  melt  only  at  22°. 

When  heated  for  a  long  time  at  130°  to  160°  in  presence  of  sulphuric  acid, 
glycerol  loses  one  or  more  molecules  of  water,  giving  anhydrides  or  ethers 
of  glycerol  or  polyglycerines  (A.  Nobel,  1890);  W.  Will  (1904)  arrived  at  the 
same  result  by  heating  glycerol  for  seven  to  nine  hours  at  290°  to  295°  and 
distilling  off  the  water  formed.  This  treatment  yields  about  60  per  cent,  of 
diglycerine,  C3H5(OH)2  •  O  *  C3H5(OH)2,  and  a  little  tri-  and  polyglycerines ;  all 
these  products  may  be  esterified  like  glycerol  and  yield,  e.  g.,  tetranitrodiglycerine, 
which  does  not  congeal  even  at  — 20°  and  has  an  explosive  power  like  trinitro- 

1  The  process  used  appears  to  be  that  of  Connstein  and  Liidecke,  based  on  the  observation 
that  the  amount  of  alcohol  formed  during  fermentation  diminishes  and  that  of  glycerol  formed 
increases  as  sodium  sulphite  is  added  to  the  saccharine  liquid  in  increasing  proportions.  The 
results  obtained  with  a  10  per  cent,  sugar  solution  containing  also  small  amounts  of  ammonium 
sulphate,  sodium  phosphate,  and  potassium  salts,  are  illustrated  by  the  following  figures : 


Sulphite  employed     . 
Glycerol    formed 
Alcohol          ,, 
Aldehyde       ,, 
Carbon  dioxide  formed 


25  50  100 

113  196  271 

400  287  233 

24  58  86 

396  358  294 


When  the  fermentation  is  finished,  the  yeast  (recoverable)  is  removed  by  filtration  and  the 
aldehyde  and  alcohol  by  distillation.  From  the  residual  liquid  salts  and  acids  are  separated  by 
means  of  calcium  chloride  and  excess  of  the  latter  by  sodium  carbonate,  the  liquid  being  filtered 
and  concentrated ;  glycerol  slightly  contaminated  with  glycol  is  thus  obtained. 


GLYCERINE 


219 


glycerine  (see  also  C.  Claessen,  Ger.  Pats.  181,754  and  198,768,  1907).  Accord- 
ing to  U.S.  Pats.  978,443  (1910)  and  13,234  (1911),  glycerol  readily  polymerises 
when  heated  at  275°  in  presence  of  0'5  to  1*0  per  cent,  of  sodium  acetate, 
70  per  cent,  being  polymerised  in  an  hour. 

When  heated  rapidly  and  strongly  it  decomposes,  yielding  partly  acrolem 
with  the  characteristic  pungent  odour.  Also  when  heated  with  P205  or 
KHS04,  it  loses  2H20,  giving  acrolem,  CH2  :  CH  •  CHO. 

One  hundred  parts  of  glycerol  dissolve  the  following  quantities  of  mineral 
salts  :  98  of  sodium  carbonate,  60  of  borax,  50  of  zinc  chloride,  40  of  potassium 
iodide,  10  of  boric  acid,  50  of  tannin ;  bromine,  ammonia,  ferric  chloride,  etc., 
are  also  dissolved. 

Glycerol  has  the  refractive  index  1*476  at  13°  and  in  aqueous  solution  the 
index  varies  proportionally  with  the  dilution.  By  means  of  Lenz's  table,  the 
concentration  of  glycerol  solutions  may  ber  determined  from  either  the  specific 
gravity  or  the  index  of  refraction  : 


Percentage 
of  glycerol 

Degrees 
Baum6, 
Beck, 
Gerlach 

Sp.gr.  at 
12°  to  14° 

Index  of 
refraction 
at  12-5°  to 
12-8° 

Percentage 
of  glycerol 

Degrees 
Baume. 
Beck, 
Gerlach 

Sp.  gr.  at 
12°  to  14° 

Index  of 
refraction 
at  12-5°  to 
12-8° 

100 

30-7 

1-2691 

1-4758 

54 

18-0 

1-1430 

1-4065 

99 

30-4          1-2664 

1-4744 

52 

17-4 

1-1375 

1-4036 

98 

30-1          1-2637 

1-4729 

50 

16-9 

1-1320 

1-4007 

97 

29-8          1-2610 

1-4715 

48 

16-2 

1-1265 

1-3979 

96 

29-6          1-2584 

1-4700 

46 

15-5 

1-1210 

1-3950 

95 

29-4          1-2557 

1-4686 

44 

15-0 

1-1155 

1-3921 

94 

29-1      !    1-2531 

1-4671 

42 

14-3 

1-1100 

1-3890 

93 

28-9      |    1-2504 

1-4657 

40 

13-6 

1-1045 

1-3860 

92 

28-7      !    1-2478 

1-4642 

38 

13-0 

1-0989 

1-3829 

91 

28-5          1-2451 

1-4628 

36 

12-3 

1-0934 

1-3798 

90 

28-2          1-2425 

1-4613 

34 

11-5 

1-0880 

1-3772 

88 

27-7 

1-2372 

1-4584 

32 

11-0 

1-0825 

1-3745 

86 

27-1 

1-2318 

1-4555 

30 

10-3 

1-0771 

1-3719 

84 

26-6 

1-2265 

1-4525 

28 

9-6 

1-0716 

1-3692 

82             26-1 

1-2212 

1-4496 

26 

9-0 

1-0663 

1-3666 

80 

25-6 

1-2159 

1-4467 

24 

8-3 

1-0608 

1-3639 

78 

25-1 

1-2106 

1-4438 

22 

7-6 

1-0553 

1-3612 

76 

24-5 

1-2042 

1-4409 

20 

6-9 

1-0498 

1-3585 

74 

24-0 

1-1999 

1-4380 

18 

6-1 

1-0446 

1-3559 

72 

23-5 

1-1945 

1-4352 

16 

5-6 

1-0398 

1-3533 

70 

23-0 

1-1889 

1-4321 

14 

4-9 

1-0349 

1-3507 

68 

22-3 

1-1826 

1-4286 

12 

3-8 

1-0297 

1-3480 

66 

21-6 

1-1764 

1-4249 

10 

3-4 

1-0245 

1-3454 

64 

21-0 

1-1702 

1-4213 

8 

2-8 

1-0196 

1-3430 

62 

20-3      !    1-1640 

1-4176 

6 

2-1 

1-0147 

1-3405 

60 

19-8          1-1582 

1-4140 

4 

1-3 

1-0098 

1-3380 

58 

19-2          1-1530 

1-4114 

2 

0-7 

1-0049 

1-3355 

56 

18-6          1-1480 

1-4091 

The  specific  gravity  may  be  corrected  for  the  temperature  by  adding  or 
subtracting  0'7  per  cent,  for  each  degree*  above  or  below  15°. 

The  specific  viscosity  (p.  90)  varies  greatly  with  the  water-content. 

Glycerol  has  the  interesting  property  of  preventing  the  precipitation  of 
various  metallic  hydroxides  (*.  e.,  it  keeps  them  dissolved);  for  instance,  in 
presence  of  glycerol,  potassium  hydroxide  does  not  precipitate  salts  of  chromium, 
copper,  etc.  With  alkalis  it  forms  slightly  stable  soluble  alkoxides.  It  does 
not  reduce  silver  or  cupric  salts,  and  hence  cannot  contain  aldehyde  groups; 


220  ORGANIC    CHEMISTRY 

it  is  not  coloured  by  concentrated  sulphuric  acid  or  by  sodium  hydroxide  on 
boiling.  The  halogens  act  on  glycerol,  not  as  substituting,  but  as  oxidising 
agents.  It  inverts  cane-sugar  and  renders  starch  soluble  ;  100  parts  of  glycerol 
and  six  of  starch  at  190°  give  starch  soluble  in  water,  and  the  starch  may  be 
separated  from  the  glycerol,  when  cold,  by  precipitation  with  alcohol. 

Like  the  other  polyhydric  alcohols  (glycols,  erythritol  and  its  isomerides, 
also  glucose  and  its  isomerides — galactose,  etc. — but  not  cane-sugar,  quercitol 
or  dextrin)  glycerol,  when  added  in  sufficient  quantity,  transforms  the  alkaline 
reaction  of  borax  solutions  into  an  acid  reaction,  thus  allowing  of  the  deter- 
mination of  boric  acid  and  borax  by  titration. 

Under  the  action  of  certain  schizomycetes,  glycerol  yields  normal  butyl 
alcohol,  butyric  acid  and,  partly,  ethyl  alcohol. 

Being  a  trihydric  alcohol,  glycerol  is  able  to  form  esters  of  three  types 
(mono-,  di-  and  tri-),  according  a*S  one,  two,  or  three  hydroxyl  groups  are 
replaced  by  inorganic  or  organic  acid  residues.  In  this  way  the  glycerides  may 
be  regenerated ;  for  example,  when  excess  of  stearic  acid  is  heated  with  glycerol 
at  200°  under  reduced  pressure  until  no  more  water  separates,  tristearin  is 
formed. 

When  cautiously  oxidised,  glycerol  forms  first  glyceric  acid,  OH  '  CH2  • 
CH'(OH)  •  COOH,  which  undergoes  further  oxidation  to  tartronic  acid, 
COOH  •  CH(OH)  •  COOH,  so  that  it  is  proved  that  glycerol  contains  two 
primary  alcohol  groups  ('  CH2  •  OH) ;  also,  as  tartronic  acid  still  exhibits 
alcoholic  characters,  it  must  contain  a  secondary  alcohol  group.  The  con- 
stitution of  glycerol  is  hence  completely  proved. 

USES  OF  GLYCEROL.  The  bulk  of  the  glycerol  manufactured  is  used 
for  the  preparation  of  nitroglycerine  and  hence  of  dynamite  (see  later) ;  to 
some  extent  it  serves  for  the  manufacture  of  glycerinacetin,  which  is  employed 
in  making  explosives  and  in  printing  textiles.  It  is  also  used  to  give  body  to 
light  wines  (termed  Scheelisation,  after  Scheele,  the  discoverer  of  glycerol). 
It  is  employed  in  the  manufacture  of  liqueurs,  syrups,  preserves,  and  sweet- 
meats, since  it  is  sweet  and  dense,  and,  to  some  extent,  anti -fermentative. 
It  is  added  to  chocolate,  tobacco,  cosmetics,  textiles  to  be  dressed,  and  leather 
goods,  since  it  does  not  dry  and  keeps  them  soft  or  pliable.  It  is  also  used  in 
extracting  from  flowers  and  herbs  delicate  perfumes  which  would  undergo 
change  if  extracted  by  distillation. 

It  is  employed  as  a  non-congealing  and  lubricating  liquid  (a  solution  of 
sp.  gr.  1'13)  in  gas-meters  and  in  hydraulic  pumps;  for  greasing  iron  objects 
to  prevent  them  from  rusting ;  for  making  copying-ink,  soap,  and  shoe-polish ; 
for  preserving  anatomical  preparations,  etc. 

INDUSTRIAL  PREPARATION.  Glycerol  is  obtained  almost  exclusively  as  a 
secondary  product  in  the  treatment  of  fats.  Until  the  year  1885  only  the  aqueous  residues 
of  stearine  works  were  worked  up  (the  fats  are  decomposed  with  lime,  sulphuric  acid, 
steam,  or  ferments),  but  nowadays  almost  all  the  alkaline  lyes  of  soap  factories  (where  the 
fats  are  treated  directly  with  caustic  soda  and  then  with  salt)  x  are  utilised. 

Of  the  9  to  11  per  cent,  of  glycerol  contained  in  fats,  8  to  10  per  cent,  may  be  recovered 
(only  4  per  cent,  when  the  decomposition  is  effected  by  sulphuric  acid,  the  maximum  yield 
being  obtained  when  water  or  enzymes  are  used). 

The  treatment  of  the  dilute  solutions  of  crude  glycerol  varies  with  their  origin  :  soap- 
lyes  (which  are  sometimes  concentrated  in  fhe  soap-works  and  sold  to  the  glycerol  refiners ) 
are  treated  with  0-1  to  0-2  per  cent,  of  lime  or  ferrous  sulphate  and  mixed  by  means  of  an 
air-jet;  the  liquid  is  decanted,  slightly  acidified  with  hydrochloric  acid  and  skimmed; 
a  small  quantity  of  aluminium  sulphate  is  then  added,  the  liquid  being  decanted,  rendered 

1  These  lyes  have  an  alkaline  reaction  and,  on  analysis,  one  of  them  (somewhat  dense)  gave 
the  following  results  :  water,  61  per  cent. ;  glycerol,  16-5  per  cent. ;  salts,  22  per  cent,  (eight- 
tenths  of  which  were  NaCl,  one-tenth  Na2SOj,  and  one-tenth  Na2C03).  The  specific  gravity 
varies  from  3°  to  7°  Be.,  and  the  proportion  of  glycerol  usually  from  6  to  12  per  cent. 


221 

slightly  alkaline,  passed  through  a  filter-press  and  concentrated  in  open  boilers  furnished 
with  stirrers  until  sodium  chloride  begins  to  separate ;  subsequent  concentration  to  the 
sp.  gr.  28°  Be.  is  carried  out  in  a  vacuum,  the  salt  deposited  being  gradually  removed. 
This  crude  glycerol  contains  85  to  90  per  cent,  of  glycerol  and  1  per  cent,  of  salts,  and  has 
a  dark  yellow  or  brownish  colour.  Sometimes  the  alkali  is  removed  from  the  soap  lyes 
by  adding  a  little  resin  and  boiling,  so  that  the  resin  soap  formed  is  carried  to  the  surface 
and  may  be  decanted  (to  be  utilised  by  adding  to  ordinary  soap). 

The  free  lime  may  also  be  precipitated  with  an  oxalate  or  with  carbon  dioxide  and 
the  sulphates  with  barium  chloride.     The  concentration  is  not  carried  out  in  open  vessels, 
as,  when  the  aqueous  solutions  are  vigorously  boiled,  the  steam  given  off  carries  away  appre- 
ciable quantities  of  glycerol.     The 
concentration  is  hence  carried  to  a 
certain  point  in  an  apparatus  (Fig. 
174  shows  the  Droux  apparatus  and 
Fig.  175  that  of  Morane),  fitted  with 
rotating   coils   or  hollow  lenticular 
discs,  in  which  steam  under  pressure 

circulates.    The  apparatus  is  covered  __^^_~- 

in  and  the  steam  from  the  solution  ^bst^PHfflP1*" - -'..'-' 
issues  rapidly  through  a  tube  com- 
municating with  an  aspirator.  When 
the  density  reaches  18°  to  20°  Be. 
the  solution  is  decanted  or  filtered 
and  then  further  concentrated  in  a  FIG.  174. 

vacuum  to  27°  to  28°  Be. 

In  some  cases  the  glycerol  thus  obtained  (or  after  dilution  with  water ),  while  still  boiling, 
is  decolorised  by  adding  animal  charcoal  and  filtering  through  a  filter-press.  This  glycerol 
always  contains  a  small  quantity  of  dissolved  salts.  To  purify  it,  its  temperature  is  raised 
to  110°  to  120°  by  means  of  superheated  steam,  the  acids  or  more  volatile  products  being 
thus  eliminated.  It  is  then  distilled  with  superheated  steam  at  170°  to  180°,  at  which 
temperature  all  the  pure  glycerol  passes  over.  This  is  rectified  in  one  apparatus  at  22°  Be. 
and  in  a  second,  under  diminished  pressure  and  with  superheated  steam,  to  28°  Be.,  at 
which  concentration  almost  all  the  salt  separates.  In  general  the  coloration  produced  on 
distillation  is  less  with  a  slightly  alkaline,  than  with  an  acid,  glycerol.  The  vacuum  distilla- 
tion is  sometimes  effected  by  a  triple-effect  apparatus  (Pick  type,  see  Vol.  I.,  p.  567;  also 

section  on  Sugar),  with  which  it  is  easy  to 
remove  the  salt,  as  it  separates  without 
interrupting  the  distillation. 

These  forms  of  apparatus  for  purifica- 
tion and  distillation  are  named  after  their 
inventors  (Hagemann,  Scott,  Jobbins, 
van  Ruymbeke,  Lehmann,  Heckmann, 
etc.). 

The  Heckmann  process  consists  in  dis- 
tilling the  aqueous  glycerine,  already  con- 
centrated to  beyond  20°  Be.,  in  a  boiler,  A 
(Fig.  176),  into  which  steam  superheated 
to  200°  to  220°  and  under  half  an  atmo- 
sphere pressure  is  passed  by  means  of  a  perforated  coil ;  the  temperature  of  the  liquid 
should  not  exceed  170°,  since  otherwise  a  small  part  of  the  glycerol  decomposes.  In 
order  to  prevent  the  scum  being  carried  over  with  the  steam  and  glycerol,  a  perforated 
disc,  o,  fitted  with  a  vent-pipe  is  fixed  two-thirds  of  the  way  up  the  boiler.  The 
vapours  issue  by  the  pipe  B,  and  are  condensed  in  the  reservoir,  C,  which  is  heated  to 
80°  to  90°  with  indirect  steam  circulating  in  the  jacketed  bottom,  D.  Above  the  reservoir 
is  a  rectifying  column,  with  a  dephlegmator,  K,  similar  to,  but  much  lower  than,  that  used 
for  the  rectification  of  alcohol  (see  p.  158). 

During  the  distillation,  a  slight  vacuum  is  maintained  in  the  whole  apparatus  by  means 
of  a  suction  pump,  V,  so  that  principally  water- vapour  and  only  a  little  glycerol  are  evolved 
from  the  reservoir,  C.  The  glycerol  vapour  separates  in  the  column  and  returns  to  the 


FIG.  175. 


222 


ORGANIC    CHEMISTRY 


reservoir,  whilst  .the  condenser,  M,  condenses  only  the  water-vapour,  which  is  controlled 
by  its  density,  colour,  and  taste  in  the  test-glass,  N,  and  is  then  collected  in  the  tank,  O. 
In  C  the  glycerol  finally  reaches  a  concentration  of  95  to  99  per  cent. 

The  rectifying  column  is  sometimes  replaced  by  a  series  of  communicating,  vertical 
copper  tubes  (Fig.  177)  which  fractionally  condense  the  glycerol-  and  water- vapours  from 
the  boiler,  B  (heated  partly  by  direct  fire),  into  which  passes  steam  from  v,  superheated 
in  the  furnace,  T.  By  means  of  the  pump,  Z,  a  vacuum  is  maintained  in  the  whole 
apparatus,  so  that,  as  the  distillation  proceeds,  fresh  glycerine  from  the  reservoir,  A,  may 
be  drawn  into  the  boiler.  In  the  first  cylinder  or  condensing  tube,  which  soon  reaches  a 


FIG.  176. 

temperature  of  100°,  almost  pure  glycerol  separates,  whilst  in  the  succeeding  tubes,  cooled 
only  by  the  surrounding  air,  more  and  more  dilute  glycerine  and  finally  water  separate. 
Below  each  tube  is  a  horizontal  cylinder,  these  serving  to  collect  the  glycerols  of  different 
concentrations,  some  of  which  are  subjected  to  redistillation.  In  this  way  is  obtained  the 
best  dynamite  glycerine,  which  must  have  a  specific  gravity  of  1-263  (98  to  99  per  cent.), 
and  should  not  contain  lime,  sulphuric  acid,  chlorine,  or  arsenic.  To  eliminate  traces  of 
colour  and  empyreumatic  products,  the  liquid  is  digested  with  boneblack  (washed  with 
acid  and  dried) ;  the  final  portions  of  water  are  expelled  by  heating  in  a  vacuum. 


FIG.  177. 

Besides  by  means  of  boneblack  or  special  vegetable  charcoal,  complete  decoloration 
may  also  be  effected  by  sodium  hydrosulphite  or,  better,  by  the  zinc-formaldehyde  sulph- 
oxylate  compound  (see  Vol.  I.,  p.  588).  Very  pure  glycerol  has  been  obtained  by  main- 
taining it  at  0°  for  some  time  and  then  inducing  crystallisation  by  a  few  pure  crystals 
obtained  separately  by  cooling  to  —  40°  (Kraut's  process).  The  degree  of  purity  is  increased 
by  a  second  crystallisation. 

Purification  by  an  osmotic  process  has  also  been  attempted  but  with  unsatisfactory 
results. 

During  the  last  few  years  the  glycerine  liquids  from  the  biological  or  catalytic  decom- 
position of  fats  (see  section  on  Fats)  have  also  been  worked  up  :  they  are  first  neutralised 


TESTING    OF    GLYCERINE 


223 


or,  better,  rendered  slightly  alkaline  with  milk  of  lime  and,  after  being  left  for  some  time, 
the  liquid  is  decanted  or  filtered  off,  concentrated  to  15°  Be.  in  vacuo,  again  allowed  to 
stand  to  deposit  a  further  quantity  of  lime,  decolorised  by  passing  through  a  carbon  filter 
and  again  concentrated  to  28°  B6. 

Various  attempts  have  also  been  made  to  recover  the  glycerine  from  the  waste  liquors 
from  the  manufacture  of  alcohol,  but  as  yet  without  much  success  (Ger.  Pats.  114,492, 
125,788,  129,578,  141,703,  and  147,558). 

STATISTICS  AND  PRICES.  The  production  and  trade  in  glycerine  (from  stearine 
and  soap-works)  in  different  countries  is  shown  by  the  following  figures  (tons) :  x 


1890 

1900 

1905 

1908 

1910 

1912 

1913 

1918 

f__-j     /stearine 
France     4  Pro   '   \soap     . 

6,000 
3,500 

— 

— 

|  12,000 

— 

14,000 

— 

— 

[exp. 

3,856 

7,450 

— 

7,000 

— 

6,811 

— 

— 

{,     /stearine 

3,000 

2,000 

.  — 

— 

— 

3,000 

— 

— 

*•       " 

exp. 

2,000 

8,000 
2,730 

— 

1,580 

— 

9,000 

-  __ 



imp. 

.  — 

— 

— 

5,373 

— 

— 

— 

— 

{,     /stearine 
P  °  '   \soap 

1,200 
5,500 

— 

1  — 

|  16,000 

— 

— 

— 

— 

exp. 

— 

— 

— 

10,000 

12,000 

— 

— 

•  —  • 

imp. 

— 

— 

— 

— 

3,360 

— 

— 

— 

{prod. 

180 

— 

190 

215 

294 

220 

505 

— 

exp. 

— 

— 

— 

833 

1,763 

2,282 

1,259 

— 

imp. 

— 

— 

— 

198 

270 

789 

761 

6,828 

(,     /stearine 
'    \soap      . 

— 

— 

10,000 
13,000 

}        - 

— 

20,000 

— 

7""* 

exp. 

.  — 

— 

— 

— 

— 

— 

•  — 

10,000 

imp. 

— 

— 

— 

16,000 

18,000 

— 

— 

— 

Whole      ~\        ,     f  stearine 
world  )Prod-  (soap     . 

26,000 
14,000 

40,000 
40,000 

— 

|  72,000 

80,000 

— 

— 

— 

The  following  qualities  of  glycerine  are  distinguished  :  2   (A)  Crude  glycerine  from  the 

1  In  1910  Spain  produced  2500  tons  of  glycerine,  893  tons  being  exported. 

The  annual  output  in  Italy  prior  to  the  war  amounted  to  about  350  tons  of  glycerine  for 
pharmaceutical  purposes,  100  tons  of  dark  glycerine  residues  for  use  on  the  railways,  and  about 
150  tons  of  pure  glycerine  for  dynamite,  for  which  also  glycerine  was  imported.  During  the 
war  the  Italian  imports  were  :  1914,  335  tons  (1094  exported) ;  1915,  791  (40  exported) ;  1916, 
1590 ;  1917,  4189,  and  1918,  6828  (almost  all  from  the  United  States),  valued  at  £2,600,000. 

Three-fourths  of  the  French  output  is  due  to  Marseilles,  where,  before  the  war,  a  single  refinery 
produced  2500  tons  yearly ;  the  exports  were  mainly  to  the  United  States. 

German  imports  and  exports  were  as  follows  (tons)  : 


1910  . 

1911  . 

1912  . 

1913  . 


Crude  Glycerine 

f  ^\ 

Imports  Exports 

4685  1688 

5143  2463 

6875  2316 

5374  2237 


Pure  Glycerine 

Imports  Exports 

914  2596 

1241  2394 

1186  3736 

1107  3937 


2  Tests  for  Glycerine  :  the  crude,  pale  at  28°  Be\,  contains  0-5  per  cent,  of  ash  and  is  not 
rendered  turbid  by  HC1,  and  only  faintly  so  by  lead  acetate ;  that  separated  from  sulphuric  acid 
saponifications,  besides  having  a  bad  smell  and  taste,  gives  3  to  5  per  cent,  of  ash  and  84  to 
86  per  cent,  of  glycerine,  a  turbidity  (fatty  acids)  or  precipitate  being  produced  by  HC1  or  lead 
acetate.  The  glycerine  to  be  used  for  nitroglycerine  and  dynamite  is  subjected  to  the  following 
tests  :  the  water  is  calculated  from  the  loss  in  weight  of  20  grams  heated  for  ten  hours  at  100 
and  for  a  few  hours  at  a  slightly  higher  temperature.  Five  grams,  after  being  heated  in  a  platinum 
dish  at  180°  until  no  further  evolution  of  vapour  takes  place,  is  weighed,  and  should  then  undergo 
no  further  diminution  in  weight  when  again  heated  for  a  short  time ;  it  is  then  ashed  in  the  usual 
way  and  the  ash  tested  for  metals  and  salts.  Glycerine  for  nitroglycerine  should  have  been  distilled 
at  least  once,  should  not  contain  sugar  or  fatty  acids,  should  have  a  neutral  reaction  and  should 
contain  no  lead,  calcium,  or  other  metals  or  foreign  metalloids ;  only  traces  of  Cl,  As,  and  Fe 
are  allowed  :  the  specific  gravity  should  exceed  1-26  at  15°.  The  purest  glycerine  (puriss). 
does  not  contain  more  than  0-03  per  cent,  of  ash  and  not  more  than  0-2  per  cent,  of  extraneous 
organic  substances  which  do  not  evaporate  at  175°,  and  for  dynamite  these  two  should  not 
exceed  0-25  per  cent.  Oxalic  acid  is  detected  by  neutralising  with  ammonia,  acidifying  with 
acetic  acid  and  precipitating  with  CaCl2.  The  glycerine  content  is  determined  from  the  density 


224  ORGANIC    CHEMISTRY 

candle-  or  soap-works ;  the  saponification  glycerine  from  candle- making  is  the  better  (since 
fats  of  higher  quality  are  used  for  candles)  and,  although  it  is  darker,  it  is  more  easily 
decolorised  than  that  from  soap  lye.  (B)  Refined  glycerine,  which  is  subdivided  into  : 
pale,  white,  for  dynamite,  and  chemically  pure. 

The  price  of  glycerine  has  undergone  considerable  fluctuation  owing  to  various  causes, 
often  to  collusion  between  speculators.  Thus  between  1867  and  1880,  it  varied  between 
£12  and  £42  per  ton,  while  financial  manoeuvres  raised  the  price  to  £88  in  1881,  since  when 
the  glycerine  of  soap  lyes  has  been  largely  utilised.  In  1884  the  price  of  dynamite  glycerine 
fell  to  £24  per  ton. 

In  1908-1909  the  price  of  No.  II  dark  brown  crude  glycerine  at  24°  Be.  was  £15  per 
ton  and  at  28°  Be.  £18;  for  the  light  brown  variety,  £23,  and  for  the  pale  at  28°  Be.  £40. 
Yellow  refined  at  28°  Be.  cost  £46 ;  white  refined  No.  I,  £48  at  28°  Be.  and  £45  at  30°  Be. ; 
free  from  lime  for  soap,  £50  at  28°  Be.  and  £54  at  30°  Be.  Finally  the  purest  double- 
distilled  for  nitroglycerine  at  31°  Be.  cost  £60  per  ton.  At  the  beginning  of  1910  these 
prices  were  increased  by  25  per  cent.,  and  towards  the  end  of  1910  by  50  per  cent,  or  even 
70  per  cent.  At  the  beginning  of  1911  they  were  still  higher,  mainly  owing  to  the  large 
amount  required  in  North  America  for  making  dynamite  for  the  Panama  Canal  and  other 
public  works.  During  the  European  War  glycerine  for  dynamite  cost  as  much  as  £320  to 
£360  per  ton. 

C.  TETRA-   AND   POLY-HYDRIC   ALCOHOLS 

These  are  usually  sweet,  crystalline  substances  which  decompose  near  their 
boiling-points.  They  are  distinguished  one  from  another  by  the  crystalline 
forms  of  their  phenylhydrazine  derivatives. 

They  do  not  reduce  Fehling's  solution,  and  hence  differ  from  the  carbo- 
hydrates, but  are  derived  from  these  by  reduction. 

The  valency  of  an  alcohol  is  given  by  the  number  of  alcoholic  hydroxyls  it 
contains,  and  hence  by  the  number  of  monobasic  acid  residues  it  can  fix  to  form 
a  neutral  ester.  Acetic  anhydride  serves  well  for  this  purpose,  the  hydrogen 
atoms  of  the  hydroxyl  groups  being  replaced  each  by  an  acetyl  group,  CH3  •  CO  : l 

C6H8(OH)6  +  6(CH3  •  C0)20  =  6CH3  •  COOH  +  C6H8(0  •  CO  •  CH3)6. 

Mannitol  Hexacetylmannitol 

(the  air-bubbles  being  removed  by  heating),  use  being  made  of  the  Table  on  p.  219 ;  in  Germany 
a  special  Berthelot  scale  is  used  indicating  one  degree  higher  than  the  Baume  scale,  26°  Berthelot 
corresponding  with  a  specific  gravity  of  1-210,  28°  with  1-230,  29°  with  1-240,  and  30°  with  1-250. 
The  index  of  refraction  is  determined  at  the  temperature  indicated  in  the  Table.  In  many  cases 
the  glycerine  is  estimated  directly  by  means  of  the  acetyl  number  (see  succeeding  Note),  but  the 
method  in  which  the  glycerine  is  oxidised  by  hot  permanganate  and  potassium  hydroxide  to 
oxalic  acid  and  the  latter  precipitated  as  calcium  oxalate  should  be  rejected.  The  fairly  rapid 
Hehner-Richardson- Jaffe  method,  improved  by  Tortelli,  is  used  more  successfully  :  the  glycerine 
is  destroyed  with  dichromate  and  sulphuric  acid,  and  the  amount  of  dichromate  used  up  (or, 
according  to  Gautter  and  Schulze,  the  amount  of  C02  evolved)  measured  by  titration  with 
sodium  thiosulphate,  or,  better,  ferrous  ammonium  sulphate.  This  method  assumes  that  the 
glycerine  contains  no  chloride,  nitrate,  or  extraneous  organic  matter;  these  impurities  may, 
in  any  case,  be  eliminated  by  means  of  silver  oxide  (chlorides),  and  lead  acetate  and  calcium 
carbonate  (organic  matter),  decoloration  being  then  effected  by  heating  with  animal  charcoal. 

1  In  this  way  is  determined  the  so-called  acetyl  number  which  is  so  widely  used  in  the  analysis 
of. fats  and  oils.  With  these,  the  test  is  made  on  the  insoluble  fatty  acids  obtained  by  saponifying 
40  to  50  grams  of  the  fat  with  40  c.c.  of  KOH  solution  (sp.  gr.  1-4)  and  40  c.c.  of  alcohol,  this 
mixture  being  heated  for  half  an  hour  on  the  water-bath,  after  which  it  is  diluted  with  a  litre 
of  water  and  boiled  for  three-quarters  of  an  hour  in  an  open  beaker  to  eliminate  the  alcohol. 
The  liquid  is  acidified  with  sulphuric  acid  and  boiled  until  the  fatty  acids  separate  in  a  trans- 
parent condition,  when  they  are  removed  by  means  of  a  separating  funnel,  washed  twice  with  hot 
water  and  dried  in  an  oven  at  100°  to  105°.  To  determine  the  acetyl  number,  a  few  grams  of 
the  substance  containing  the  hydroxyl  groups  (or  about  20  grams  of  hydroxylic  fatty  acids) 
is  treated  with  two  or  three  times  its  volume  of  acetic  anhydride  and  a  few  drops  of  concen- 
trated sulphuric  acid  (formerly  in  place  of  the  sulphuric  acid  fused  sodium  acetate,  in  quantity 
equal  to  the  acetate  anhydride,  was  used,  the  mixture  being  heated  for  two  hours  on  the  water- 
bath  in  a  reflux  apparatus).  The  mass  heats  spontaneously,  and  in  a  few  minutes  acetylation 
takes  place ;  it  is  then  allowed  to  cool,  calcium  carbonate  being  added  to  precipitate  the  sulphuric 
acid,  and  the  liquid  filtered.  The  filtrate  is  distilled  or  evaporated  to  separate  the  acetate  in  a 
liquid  or  crystalline  condition. 

In  the  case  of  the  fatty  acids,  the  filtrate  is,  however,  diluted  with  600  to  700  c.c.  of  water 


MANNITOL  225 

Esters  may  also  be  prepared  with  bromobenzoic  acid,  the  bromine  in  the 
resultant  product  being  determined  and  the  number  of  hydroxyl  groups 
deduced  therefrom.  Well-defined  compounds  are  also  formed  with  benzal- 
dehyde  and  are  employed  in  separating  the  constituents  of  different  mixtures. 

ERYTHRITOL  (Butantetrol),  OH  •  CH2  •  CH(OH)  •  CH(OH)  •  CH2  •  OH,  is  found  in 
nature  in  the  free  state  in  Protococcus  vulgaris,  and  as  orsellinic  ester  (erythrin)  in  lichens  and 
other  algae.  It  forms  crystals,  m.-pt.  112°,  b.-pt.  330°,  and  is  slightly  soluble  in  alcohol  and 
insoluble  in  ether.  It  is  obtained  by  decomposing  d-glucose  or  synthetically  from  croto- 
nylene,  and  its  constitution  is  deduced  from  the  fact  that  it  yields  secondary  normal  butyl 
iodide  on  reduction  with  hydriodic  acid.  A  similar  reaction  takes  place  with  the  higher 
polyvalent  alcohols  with  normal  chains.  The  four  possible  stereoisomerides  are  known, 
the  most  common  being  the  one  now  described,  which  is  optically  inactive. 

PENTA-ERYTHRITOL  has  the  formula  C(CH2  •  OH))4,  and  melts  at  253°. 

ARABITOL,  C5H7(OH)5  (Pentahydroxypentane),  crystallises  in  acicular  prisms, 
m.-pt.  102°,  has  a  sweet  taste  and  is  formed  by  reducing  the  corresponding  sugar,  arabinose, 
with  nascent  hydrogen ;  reduction  of  xylose  similarly  yields  xylitol. 

MANNITOL,  C6H8(OH)6  (Hexanhexol),  occurs  abundantly  in  the  vegetable  kingdom 
(the  larch,  celery,  sugar-cane,  Agaricus  integer  containing  20  per  cent,  of  mannitol,  etc.), 
but  especially  in  the  manna  ash  (Fraxinus  ornus),  the  dried  juice  of  which  forms  ordinary 
manna  ;  x  from  this  alcohol  extracts  pure  mannitol,  which  may  be  decolorised  by  repeated 

and  boiled  for  thirty  to  forty  minutes  in  an  open  beaker  to  remove  the  acetic  acid,  a  slow  current 
of  C02  being  passed  into  the  bottom  of  the  liquid  to  prevent  bumping.  The  supernatant  liquid 
is  then  siphoned  from  the  acetyl  compound,  which  is  boiled  with  another  500  c.c.  of  water  and 
so  on,  this  operation  being  repeated  until  the  washing  water  no  longer  has  an  acid  reaction. 
The  acetylated  derivative  is  then  collected  on  a  filter,  washed  and  dried  in  an  oven. 

Of  this  compound,  0-5  to  Igram  is  dissolved  in  pure,  neutral  alcohol,  and  the  solution  heated 
for  forty-five  minutes  on  the  water-bath  in  a  150  c.c.  flask,  fitted  with  a  reflux  condenser,  with 
a  definite  volume  (30  to  50  c.c.)  of  seminormal  alcoholic  potash.  When  cold,  the  liquid  is  titrated 
with  seminormal  hydrochloric  acid  in  presence  of  phenolphthalein  to  determine  the  excess  of  alkali 
which  has  not  taken  part  in  the  splitting  of  the  acetic  ester. 

One  hydroxyl  group  for  every  gram-mol  of  substance  corresponds  with  56  grams  of  KOH 
fixed.  With  the  fatty  acids,  which  contain  also  the  carboxyl  group,  the  procedure  is  as  follows  : 
3  to  4  grams  of  the  acetyl  derivative  is  dissolved  in  pure,  neutral  alcohol  and  the  acidity  of  the 
carboxyl  group  (acetyl  acid  value)  determined  by  titration  with  N/2-alkali ;  the  neutralised  liquid 
is  boiled  with  a  known  volume  in  excess  of  N/2-alcoholic  potash  for  a  short  time  on  the  water- 
bath,  retitration  with  N/2 -hydrochloric  acid  giving  the  excess  of  alkali  not  combined  with  acetyl 
groups.  The  alkali  combined  (after  the  first  neutralisation),  expressed  in  mgrms.  of  KOH 
per  1  gram  of  acetyl  compound  gives  the  acetyl  number.  With  the  fatty  acids  the  sum  of  the 
acetylated  acid  number  and  the  acetyl  number  is  termed  the  acetyl  saponification  value.  From 
the  acetyl  number  (N),  the  molecular  magnitude  (M ),  of  the  alcoholic  substance  may  be  deduced 

«,     *         i        Tut       56'100       ,o 
by  the  formula  :  M  =  — ^ — -  —  42. 

1  Manna  is  extracted  more  particularly  from  Fraxinus  ornus  and  Fraxinus  rotundifdia, 
which  are  widespread  in  Sicily  and  Calabria  and  from  which  it  readily  flows  through  long  vertical 
incisions  made  in  summer  and  autumn.  It  seems  to  occur  in  the  rising  sap  before  this  reaches 
the  leaves,  and  is  thought  by  some  to  be  produced  by  enzyme  actions.  Crude,  commercial  manna 
contains  12  to  13  per  cent,  of  water,  10  to  15  per  cent,  of  sugar,  32  to  42  per  cent,  of  mannitol, 
40  to  41  per  cent,  of  mucilaginous  substances,  organic  acids  and  nitrogenous  matter,  1  to  2  per 
cent,  of  insoluble  substances  and  1  to  2  per  cent,  of  ash.  Australian  manna  (from  Myoporum 
platycorpum)  contains  as  much  as  90  per  cent,  of  mannitol.  '  In  the  neighbourhood  of  Palermo, 
Fraxinus  roslrata,  which  gives  an  inferior  manna,  is  cultivated. 

The  manna  tree  grows  in  fertile,  dry  and  even  rocky  soil  and  is  incised  in  its  tenth  year  and  in 
the  following  ten  or  fifteen  years.  It  is  then  cut  back  and  the  new  branches  incised  in  the  seventh 
year  and  the  succeeding  ten  or  fifteen  years.  It  is  then  again  cut  back,  this  procedure  being 
continued  for  eighty  or  a  hundred  years.  One  hectare  with  4500  trees  gives  as  much  as  100  kilos 
of  manna  per  annum.  It  is  harvested  in  August  and  September. 

Manna  is  used  as  a  mild  purgative  for  children.  It  has  a  sweetish  taste,  is  soluble  in  water 
or  alcohol,  and,  besides  mannitol,  contains  various  sugars  such  as  stachyose  and  mannalriose. 

To  extract  the  mannitol,  the  crude  manna  is  dissolved  in  half  its  weight  of  water  containing 
white  of  egg.  The  solution  is  boiled  for  a  few  minutes  and  strained,  and  the  filtered  mass, 
solidified  by  cooling,  pressed  in  bags,  or,  better,  centrifuged  and  washed  at  the  same  time  with 
a  large  quantity  of  cold  water.  It  is  redissolved  in  water  and  the  solution  boiled  with  animal 
charcoal,  filtered  under  pressure,  crystallised  and  centrifuged.  The  mother-liquors  are  used  to 
dissolve  fresh  quantities  of  the  crude  manna.  The  fineness  of  the  crystals  depends  on  the  con- 
centration and  on  the  temperature  of  the  air;  in  some  cases  the  crystallisation  is  disturbed  by 
continually  stirring  the  mass. 

VOL.  II.  15 


226  ORGANIC    CHEMISTRY 

treatment  with  charcoal.  In  manna  it  was  discovered  by  Proust  in  1806.  It  is  obtained 
synthetically  by  reducing  fructose  or  glucose  :  C6H12O6  +  H2  =  C6H14O6. 

The  optically  inactive,  Isevo-  and  dextro-rotatory  forms  are  known,  the  last  being  the 
most  common ;  the  optical  activity  is  slight,  but  is  rendered  more  apparent  by  the  addition 
of  borax.  When  heated  it  loses  water  giving  anhydrides  (mannitan,  C6H12O5,  and  mannide, 
C6H10O4);  in  a  vacuum  it  distils  unchanged. 

One  hundred  parts  of  water  dissolve  16  parts  by  weight  of  mannitol  at  16°. 

From  alcohol  it  crystallises  in  triclinic  acicular  prisms  and  from  water  in  large  rhombic 
prisms  having  a  sweet  taste  and  melting  at  160°. 

Stereoisomeric  with  mannitol  is  DULCITOL,  C6H8(OH)6,  which  occurs  in  a  number 
of  plants  and  in  Madagascar  manna.  It  forms  sweet,  monoclinic  prisms,  m.-pt.  188°,  and 
is  almost  insoluble  in  water,  even  in  the  hot.  Synthetically  it  may  be  prepared  by  reducing 
lactose  and  galactose.  It  is  optically  inactive  even  in  presence  of  borax. 

Another  stereoisomeride  of  mannitol  is  sorbitol,  which  melts  at  104°  to  109°,  or  at  75° 
when  crystallised  with  1H20.  It  may  be  obtained  synthetically  by  reducing  d-glucose 
or  d-fructose.  In  presence  of  borax  it  shows  a  slight  dextro-rotation. 

Other  stereoisomerides  are  TALITOL  and  IDITOL;  these  isomerides  are  usually 
separated  by  means  of  the  acetals  they  form  with  benzaldehyde. 


DD.    DERIVATIVES    OF   THE   ALCOHOLS 

A.  DERIVATIVES   OF   MONOHYDRIC   ALCOHOLS 

I.   ETHERS 

These  are  generally  formed  by  eliminating  1  mol.  of  water  (for  example, 
by  concentrated  sulphuric  acid  or  by  hot  hydrochloric  acid)  from  2  mols.  of 
alcohol,  which  condense  to  form  1  mol.  of  ether  in  the  same  way  as  2  mols.  of 
an  acid  give  an  anhydride  : 

C2H5  •  OH  _  TT  n   ,   C2H5v.~ 

CH3  -OH  i"  CH3  ' 

Ethers  are  not  formed  by  secondary  or  tertiary  alcohols.  The  first  term  of  the 
series,  methyl  ether,  is  gaseous,  and  the  succeeding  terms  become  liquid  and 
then  solid  as  the  molecular  weight  increases,  the  ethereal  odour  of  the  first 
members  being  gradually  lost. 

The  empirical  formulae  of  the  ethers  show  them  to  be  isomeric  with  the 
alcohols,  but  their  constitution  results  from  Williamson's  synthesis,  according 

Sometimes  the  manna  solutions  are  first  subjected  to  lactic  fermentation,  by  which  means 
considerable  quantities  of  calcium  lactate  are  obtained  ;  the  mannitol  is  then  extracted  from  the 
residual  liquors. 

Mannitol  is  not  fermented  by  beer-yeast,  but  with  chalk  and. sour  cheese  it  gives  a  consider- 
able amount  of  alcohol,  volatile  acids,  carbon  dioxide,  and  hydrogen.  When  cautiously  oxidised 
with  nitric  acid,  it  forms  d-mannose  and  rf-fructose,  whilst  with  the  Sorbose  bacterium  it  gives 
only  the  latter  sugar. 

Mannitol  has  a  slight  Isevo-rotation  (—  15°)  which  is  increased  by  alkali  and  changed  in  sign 
by  borax.  It  dissolves  in  6-5  parts  of  water  at  18°,  in  80  parts  of  60  per  cent,  alcohol  at  15°, 
or  in  1400  parts  of  absolute  alcohol ;  it  is  insoluble  in  ether. 

Manna  in  casks  costs  3s.  to  5s.  per  kilo;  assorted,  Is.  Id. ;  in  lumps,  §\d.  The  average 
price  of  manna  (from  Cefalu)  on  the  Genoa  Exchange  gradually  rose  from  about  2s.  Id. 
in  1901  to  about  4s.  Id.  in  1910,  when  pure  crystallised  mannitol  cost  7s.  to  10s.  per  kilo.  The 
best  qualities  of  manna  are  those  from  Cefalu,  Gerace,  and  Smauro ;  of  inferior  quality  is  the 
Capaci  variety,  which  is  produced  also  at  Cinisi,  Belmonte,  Castellamare  del  Golfo,  etc.  The 
Sicilian  production,  which  represents  almost  the  entire  production  of  the  world,  was  about  360 
tons  in  1900,  700  in  1902,  510  in  1905,  690  in  1906,  455  in  1908,  and  less  than  300  (owing  to  the 
bad  season)  in  1910.  The  output  of  mannitol  in  1910  was  50  tons,  but  usually  about  300  tons 
of  manna  are  treated  per  annum  for  the  production  of  mannitol — about  100  tons — one-third  or 
one-fourth  of  which  is  consumed  in  Italy. 

The  exports  of  manna  from  Italy  are  as  follows  (tons)  : 

1908         1910  1912  1913  1914          1915          1916          1917     ,      1918 

Tons     .          .          178      312  377      350  267      231  278      245  206 

Value,  £         .    26,285       —       105,560       —       48,510       —       83,400       —       70,000 


ETHERS  227 

to  which  they  are  obtained  by  the  action  of  a  sodium  alkoxide  on  the  halogen 
derivative  of  an  alcohol  : 

CmH2m+1ONa  +  ICnH2n+1  =  Nal  +  CwH2m+1  •  O  •  CnH2n+1 

If  in  the  sodium  alkoxide  the  sodium  were  not  united  to  the  oxygen,  b.ut 
directly  with  carbon,  this  reaction  would  give  an  alcohol  and  not  an  ether; 
indeed,  if  sodium  ethoxide  were  NaCH2  •  CH2  •  OH,  it  would,  with  methyl  iodide, 
give  propyl  alcohol  :  CH3I  +  NaCH2  •  CH2  •  OH  =  Nal  +  CH3  •  CH2  •  CKj  '  OH. 
In  reality,  however,  methyl  ethyl  ether,  and  not  propyl  alcohol,  is  obtained,  this 
proving  the  constitution  of  the  metallic  alkoxides  and  of  the  ethers,  in  which 
all  the  hydrogen  atoms  are  equivalent. 

The  interaction  of  silver  oxide  with  alkyl  halides  (see  p.  17)  also  leads  to 
the  formation  of  ethers  :  2C2H5I  +  Ag20  =  2AgI  +  C2H5  •  O  •  C2H5, 

If  the  alkyl  radicles  of  an  ether  are  similar,  it  is  a  simple  ether,  e.  g.,  ethyl 
ether,  C2H5  •  0  '  C2H5,  whereas  if  the  radicles  are  different,  the  result  is  a 
mixed  ether,  e.  g.,  methyl  ethyl  ether,  C2H5  •  0  '  CH3. 

Sabatier,  Senderens,  and  Mailhe  (1909-1910)  obtained  ethers  of  different  types,  some 
mixed  and  of  the  aromatic  series,  by  passing  the  superheated  vapours  of  alcohols  (250°  to 
350°)  over  metallic  oxides  (titanium,  thorium,  tungsten,  or,  best  of  all,  aluminium).  The 
yield  is  quantitative,  no  ethylene  hydrocarbons  being  formed,  as  is  the  case  when  sulphuric 
acid  is  used.  The  process  is  continuous  and  pseudo-  catalytic,  unstable  aluminium  alkoxide 
being  formed  as  an  intermediate  product  :  (C2H5O)6A12  —  A1203  +  3(C2H5)2O.  In  some 
cases  this  general  method  may  be  advantageously  employed  industrially. 

When  the  ethers  are  prepared  from  the  alkoxides  in  alcoholic  solution  there  should  not 
be  an  excess  of  water  (more  than  50  per  cent.  )  present,  otherwise  the  alkoxide  decomposes 
into  alcohol  and  alkali  hydroxide  and  no  ether  is  formed. 

Also  when  sulphuric  acid  (or  HC1)  is  used  in  the  preparation,  an  equilibrium  sets  in 
between  the  reacting  products  —  intermediate  and  final  —  this  equilibrium  being  regulated 
by  the  mass  law,  so  that  a  certain  yield  cannot  be  exceeded  except  by  eliminating  some 
of  the  new  products  formed  (e.  g.,  by  gradually  distilling  the  ether;  see  later)  : 


(a)  C2H5  •  OH  +  H2S04  =  C2H5  •  S04  H  + 

Ethylsulphuric  acid 

(6)  C2H5  •  S04H  +  C2H5  •  OH  -  H2S04  +  C2H5  •  O  •  C2H5. 

The  sulphuric  acid  is  regenerated  and  can  transform  fresh  alcohol  into  ether  ;  theoreti- 
cally, then,  the  initial  quantity  of  sulphuric  acid  should  be  sufficient  to  transform  an 
infinite  quantity  of  alcohol  into  ether,  but  in  practice  it  is  necessary  to  add  a  small  quantity 
of  the  acid  each  time,  as  some  of  it  is-oised  up  in  the  formation  of  sulphur  dioxide,  ethylene, 
and  sulphonated  products.  Thus,  in  practice  the  process  is  not  continuous  in  the  strict 
sense  of  the  term,  since  in  the  phase  (a)  water  is  formed,  and  this  cannot  all  be  eliminated 
by  distillation,  but  after  a  time  accumulates  in  such  quantity  as  to  establish  an  equilibrium 
between  the  formation  of  ether  and  the  decomposition  of  ethylsulphuric  acid,  alcohol  and 
sulphuric  acid  thus  being  regenerated. 

The  ethers  are  very  stable  and  scarcely  react  in  the  cold  with  alkalis,  dilute 
acids,  sodium  or  phosphorus  pentachloride.  When  superheated  with  water 
and  a  little  mineral  acid,  ether  is  converted  back  into  alcohol  : 

C2H5  •  0  •  C2H5  +  H2S04  =  C2H5  •  OH  +  C2H5  •  S04H, 

and  the  same  change  occurs  on  saturating  ether  at  0°  with  gaseous  hydrogen 
iodide  : 

(C2H5)20  +  HI  =  C2H5  •  OH  +  C2H5I, 

the  hydrogen  iodide  subsequently  converting  the  alcohol  also  into  ethyl  iodide  ; 
when  mixed  ethers  are  taken,  the  iodine  unites  preferably  with  the  radicle 


228  ORGANIC    CHEMISTRY 

containing  the  lesser  amount  of  carbon.     PC15  also  decomposes  the  ethers  on 
heating : 

(C2H5)20  +  PC15  _  POC13  +  2C2H5C1. 

The  halogens  give  substitution  products  just  as  they  do  with  the  hydro- 
carbons, but  nitric  acid  gives  oxidation  products. 

In  the  ethers  are  reproduced  all  the  cases  of  isomerism  presented  by  the 
alkyl  groups  from  which  they  are  derived,  there  being  consequently  numerous 
cases  of  metamerism  (see  p.  18),  e.  g.,  methyl  amyl  ether,  CH3  •  0  '  C5Hn,  is 
metameric  with  ethyl  butyl  ether,  C2H5  *  0  •  C4H9,  and  also  with  dipropyl 
ether,  C3H7  •  O  *  C3H7,  all  these  having  the  empirical  formula  C6H140. 

METHYL  ETHER,  CH3  •  O  •  CH3  (Methoxymethane),  is  a  gas,  but  liquefies  at 
—  23°,  and  then  has  the  sp.  gr.  1-617;  it  resembles  ethyl  ether.  One  volume  of  water 
dissolves  37  vols.  of  the  gas,  and  1  vol.  of  sulphuric  acid  600  vols.  of  it. 

ETHYL  ETHER,  C4H10O  (Ethoxyethane),  C2H5  •  0  •  C2H5.  This  was  pre- 
pared for  the  first  time  in  the  sixteenth  century  by  Valerius  Cordus  from  spirit 
of  wine.  It  was  formerly  thought  to  contain  sulphur,  and  was  therefore  given 
the  name  sulphuric  ether,  still  in  use.  Its  true  composition  was  established  by 
Saussure  and  by  Gay-Lussac  (1807  and  1815),  and  the  constitution  was  enun- 
ciated by  Laurent  and  Gerhardt  and  confirmed  experimentally  by  Williamson. 
It  was  thought  for  a  long  time  that  the  sulphuric  acid  employed  in  the  manu- 
facture of  ether  possessed  the  sole  function  of  fixing  and  subtracting  water 
from  the  alcohol.  Since,  however,  it  was  found  that  water  formed  in  the 
reaction  always  distilled  with  the  ether,  this  hypothesis  became  invalid,  and 
Berzelius  and  Mitscherlich  attributed  the  reaction  of  etherification  to  the 
catalytic  action  of  the  sulphuric  acid. 

Later  on  Liebig  maintained  that  the  ether  is  formed  by  the  direct  decom- 
position of  the  intermediate  product  (ethylsulphuric  acid)  with  separation, 
in  the  hot,  of  S03.  Graham,  however,  succeeded  in  showing  that  ethylsulphuric 
acid,  when  heated  alone  at  140°,  does  not  give  ether,  but  that  the  latter  is 
formed  in  presence  of  alcohol.  In  1851  Williamson  gave  the  true  explanation 
of  the  process  by  dividing  the  reaction  into  two  phases  (a  and  b,  see  preceding 
page) ;  the  secondary  products,  explaining  the  loss  of  sulphuric  acid  (see  above), 
were  discovered  later. 

Etherification  takes  place  also  if  the  sulphuric  acid  is  replaced  by  phos- 
phoric, arsenic,  boric,  or  hydrochloric  acid. 

Sulphur  dioxide,  which  is  formed  and  lost  in  this  process,  is  not  produced 
if  the  sulphuric  acid  is  replaced  by  an  aromatic  sulphonic  acid,  for  instance, 
C6H5  '  S03H,  or.  the  corresponding  chloride,  C6H5  •  S02C1  (Kraft  and  Ross, 
Ger.  Pat.  69,115),  the  temperature  of  the  reaction  being  then  slightly  above 
100°: 

(a)  C2H5  •  OH  +  C6H5  •  S03H  -  H20  +  C6H5  •  S02  •  OC2H5. 

(b)  C2H5  •  OH  +  C6H5  •  S02  •  OC2H5  =  (C2H5)20  +  C6H5  •  S03H. 

J.  W.  Harris's  process  (U.S.  Pat.  711,656)  may  have  an  industrial 
future;  in  this,  acetylene  and  hydrogen  give  ethylene  which,  with  H2S04, 
forms  ethylsulphuric  acid,  the  latter  then  forming  ether  under  the  action  of 
water. 

Good  results  are  also  given  by  the  use  of  methionic  acid,  ~CH2(S03H)2, 
proposed  by  Schroeter  and  Sondag  in  1908 ;  with  this  acid  all  the  higher  ethers 
may  be  prepared  and  10  per  cent,  of  the  acid  (on  the  weight  of  alcohol)  is 
sufficient  to  give  a  continuous  distillation  of  ether. 

Senderens  transforms  alcohol  vapour  quantitatively  into  ether  by  passing 
it  over  calcined,  precipitated  alumina  heated  exactly  to  260°  (see  p.  227). 

PROPERTIES.     Ether  is  a   colourless,    very   mobile   liquid   of    pleasant 


ETHYL    ETHER  229 

odour,  boiling  at  34-9°,  solidifying  at  —  129°  if  dry,  and  at  —40°  if  aqueous, 
and  melting  at  —113° ;  it  has  the  sp.  gr.  0'712  at  25°,  0*7196  at  15°,  0*7289  at 
6*9°,  or  0*736  at  0°.  Contamination  of  ether  by  water  and  alcohol  may  be 
detected  at  once  by  the  specific  gravity,  which  reaches  the  value  0*735  at  15° 
when  the  maximum  proportion  of  water,  namely,  7*5  per  cent.,  is  present. 
Commercially  the  density  of  ether  is  given  in  degrees  Baume  (scale  for  liquids 
lighter  than  water). 

The  vapour  density  of  ether  at  various  temperatures  in  millimetres  of 
mercury  is  as  follows  : 

Temperature    —  20°     — 10°          0°          + 10°       20°        30°        40°        50°          70°          90°         110°        120° 
Pressure       .     G7'5        113-4        183'4        286'4        433        636        910        1271        2308        3898        6208        7702 

On  evaporation,  it  produces  intense  cold.  It  inflames  very  readily,  but  is 
not  inflammable  when  mixed  with  35  to  50  per  cent,  of  carbon  tetrachloride. 
With  air  it  forms  explosive  mixtures  (p.  34).  It  is  obtained  anhydrous  by 
distilling  over  a  little  sodium. 

J.  Meunier  (1907)  has  found  that  mixtures  of  ether  vapour  and  air  are 
inflammable  and  explosive  when  they  contain  between  75  and  200  mgrms. 
of  ether  per  litre  of  air. 

As  ether  vapour  is  much  heavier  than  air  (mol.  wt.  74),  it  tends  to  collect 
in  a  dense,  invisible  layer  on  the  floor  or  bench  and  may  cause  fire  or  explosion. 
It  is  soluble  in  concentrated  hydrochloric  acid.  In  the  pure,  dry  state  it  is 
stable  in  the  air,  but  it  assumes  an  acid  reaction  if  water  or  alcohol  is  present. 

Water  dissolves  6*5  per  cent,  of  ether  at  19°,  and  ether  dissolves  about 
2'25  per  cent,  of  water  at  20°.  When  20  c.c.  of  water  is  shaken  in  a  cylinder 
with  20  c.c.  of  pure  ether  and  then  left  at  rest,  the  volume  of  the  aqueous  layer 
increases  by  2  c.c.  (solubility  of  ether  in  water ;  a  small  portion  of  the  water 
passes  into  the  ether) ;  if  the  ether  contain  alcohol,  the  increase  in  volume 
of  the  water  will  be  greater  than  2  c.c.,  whilst  if  much  alcohol  be  present,  a 
single  solution  will  be  formed.  Addition  of  water  to  a  solution  of  one  part 
of  ether  in  three  parts  of  alcohol  results  in  dissolution  of  the  water  and  in 
separation  of  a  little  of  the  ether,  whilst  in  a  solution  of  one  part  of  ether  in 
four  parts  of  alcohol  water  dissolves  without  causing  separation  of  ether. 
Aqueous  ether  may  be  recognised  by  the  turbidity  produced  on  shaking  it 
with  a  small  quantity  of  carbon  disulphide.  Ether  dissolves  in  large  amount 
in  sulphuric  acid  (monohydrate),  forming  ethylsulphuric  and  ethionic  acids 
and  ethyl  sulphate ;  92*5  per  cent,  sulphuric  acid  readily  dissolves  ether  almost 
or  quite  unchanged,  but  when  heated,  this  solution  forms  ethyl  sulphate  and 
ethionic  acid,  which  at  a  high  temperature  yields  ethylene  (1  vol.  of  sulphuric 
acid  dissolves  1*67  vols.  of  ether).  If,  however,  the  sulphuric  acid  is  diluted 
to  55°  Be.  (after  fixation  of  the  ether),  the  ether  may  be  recovered  more 
completely  (see  note,  p.  232). 

It  is  an  excellent  solvent  for  many  organic  substances,  especially  for  fats. 
It  combines  with  certain  inorganic  substances  (chlorides  of  tin,  aluminium, 
phosphorus,  antimony,  etc.)  as  ether  of  crystallisation.  With  chlorine  in  the 
cold  it  gives  successively  :  monochloroethyl  ether,  CH3  •  CHC1 *  0  '  C2H5  (b.-pt. 
98°);  ethyl  dichloroethyl  ether,  CH2C1  •  CHC1  •  0  •  C2H5  (b.-pt.  145°);  ethyl 
trichloroethyl  ether,  CHC12  •  CHC1  •  0  •  C2H5  (b.-pt.  170°  to  175°),  and  penta- 
chloroethyl  ether,  (C2C15)20,  which  boils  at  68°,  decomposing  into  C2C16  and 
trichloroacetyl  chloride,  CC13  •  CO  •  Cl.  Ether  dissolves  Br,  I,  FeCl3,  HgCl2, 
AuCl3,  and  chromic  acid. 

The  action  of  light  on  ether  produces  small  quantities  of  hydrogen  peroxide, 
acetaldehyde,  acetic  acid,  and  vinyl  alcohol.  In  contact  with  platinum  black 
it  ignites.  When  poured  into  a  cylinder  of  chlorine  it  explodes  and  forms 
hydrogen  chloride,  whilst  in  the  dark  the  slow  reaction  yields  perchloroether. 


230 


ORGANIC    CHEMISTRY 


Ether  is  an  anaesthetic  and  was  used  as  such  before  chloroform;  it  is  again 
coming  into  use  at  the  present  time,  as  it  is  less  dangerous,  although  it  produces 
certain  disturbing  effects,  for  example,  in  the  lungs.  For  this  purpose  it 
must  be  used  in  a  highly  purified  condition;  use  of  a  cork  in  the  bottle  is 
sufficient  to  alter  it. 

When  mixed  with  liquid  carbon  dioxide,  it  lowers  the  temperature  to  79'5° 
below  zero.     It  decomposes  at  above  500°,  giving  acetaldehyde. 

INDUSTRIAL  PREPARATION  OF  ETHER.  Use  was  formerly  made  in  many 
works  of  Sussenguth  vessels,  which  are  double-walled  and  made  of  iron  and  lead-lined. 
Later  large  iron  pots,  homogeneously  leaded,  were  adopted,  these  being  heated  by  high- 
pressure  steam  circulating  either  through  a  jacket  or  false  bottom,  or,  more  efficiently, 
through  leaded  copper  coils 
arranged  inside  the  vessel 
(e.  g.,  Barbet  type,  Fig. 
178).  At  135°  to  140°, 
however,  these  wear  out 
within  a  few  months,  even 
when  made  of  heavy  lead 
castings.  Hempel  endea- 
voured to  lessen  this  trouble 
by  making  the  lower  half 
of  the  vessel  of  a  single 
casting  of  hard  lead,  with 
the  heating  coils  in  the 


FIG.  178. 


FIG.  179. 


thickness  of  the  walls;   such  vessels,  although  very  expensive,  are  highly  durable  and 
require  less  frequent  repair. 

Until  a  few  years  ago  crude  ether,  contaminated  with  water,  alcohol  and  sulphur 
dioxide  was  made  and  then  subjected  to  purification  and  rectification  in  another  part  of 
the  works.  Nowadays,  however,  general  use  is  made  of  continuous  process  plants,  which 
give  directly  pure  ether,  these  being  constructed  by  Messrs.  Barbet  (France),  Eckelt 
(Berlin),  and  F.  H.  Meyer  (Hanover).  Fig.  179  shows  the  arrangement  of  an  ether  plant 
designed  by  H.  Meyer  :  The  pot  a  contains  the  mixture  of  alcohol  (5  parts  of  90  per  cent., 
free  from  fusel  oil)  and  sulphuric  acid  of  66°  Be.  (9  parts,  free  from  nitric  and  nitrosyl- 
sulphuric  acids  when  copper  vessels  are  used),  this  being  heated  by  means  of  indirect  steam 
to  the  temperature  at  which  ether  forms.  From  the  tank  a',  situated  just  under  the  roof, 
a  continuous,  regular  stream  of  alcohol  flows  into  a,  and  is  there  converted  into  crude  ether, 
the  vapour  of  which,  after  traversing  the  safety  vessel  b,  where  spray  is  retained,  is  washed 
with  soda  solution  in  the  column  c  and  then  rectified  in  the  column/.  Here  mainly  the 
water  and  alcohol  are  condensed,  the  aqueous  alcohol  descending  to  the  rectifying  column 


MANUFACTURE    OF    ETHER 


231- 


.w'j,  where  the  water  is  discharged  at  the  bottom,  while  the  alcohol  vapour  passes  to  the 
dephlegmator  i3  and  then  to  the  condenser  &;  the  pure  concentrated  alcohol  is  collected 
in  the  tank  m.  The  rectified  ether  vapour  from  the  column  j^  proceeds  to  the  dephleg- 
mator /2/3,  and  the  liquid  ether  through  the  three  purifying  and  drying  cylinders  g,  gv  and 
<72  to  the  carboys  ss.  The  ether  vapour  escaping  from  g,  gv  and  gz  is  condensed  in  the 
coil  h  by  means  of  brine  from  a  refrigerating  plant  and  the  condensate  collected  in  hv 

Some  manufacturers  use  a  mixture  of  5  parts  of  95  per  cent,  alcohol  and  12  parts  of 
sulphuric  acid  of  66°  Be. 

Theoretically  124-3  parts  of  pure  alcohol  are  required  per  100  parts  of  ether.  The 
practical  yield  of  ether  is  about  95  per  cent,  of  the  theoretical,  about  0-5  kilo  of  sulphuric 
acid  being  consumed  per  100  kilos  of  ether. 

Heckmann's  apparatus  for  working  on  a  small  scale  is  shown  in  Fig.  180 :    A  is  the 
alcohol  reservoir  which  feeds  the  alcohol  regularly  through  the  tap,  a,  and  the  glass  vessel, 
6,  to  the  still,  B,  containing  the  sulphuric  acid ;  indirect  steam  under  pressure  is  supplied 
to  the  coil,  e.     The  ether  continually  distilling  over 
is  condensed  in  the  coil,  C,  immersed  in  cold  water. 

The  premises  where  the  distilling  apparatus  is 
situated  are  usually  separated  by  thick  walls  from  the 
condenser,  in  order  to  avoid  the  danger  of  fire  and 
explosion.  Some  premises  are  fitted  with  channels 
and  draught-apparatus  for  rapidly  dispersing  any 
vapour  which  may  find  its  way  into  the  air.  The 
distilled  vapour  is  condensed  in  closed  apparatus,  the 
only  outlet  to  which  is  a  tube  opening  on  the  roof. 
The  maximum  detonation  occurs  when  1000  litres  of 
air  contains  125  grams  of  ether  vapour,  but  slight 
detonations  also  take  place  with  38  grams  or  200 
grams  of  the  vapour;  in  the  last  case  the  gaseous 
mass  is  inflamed  by  a  lighted  substance  or  an  electric 
spark. 

If  the  temperature  of  etherification  exceeds  140°, 
the  yield  diminishes,  as  a  considerable  quantity  of 
ethylene  is  then  formed  :  C2H5  •  OH  =  H20  +  C2H4. 
On  the  other  hand,  if  the  temperature  falls  below 
130°,  a  large  amount  of  alcohol  distils  without 
reacting. 

The  alcohol  for  making  ether  is  denatured  so  as  to 
be  exempt  from  taxation,  and  in  Germany  animal 
oil  (Dippel's)  is  added,  this  being  then  fixed  and 
decomposed  by  the  sulphuric  acid.  In  Italy  the 
alcohol  is  denatured  with  sulphuric  acid. 

D.  Annaratone  (Ger.  Pat.  231,395,  1909)  obtains  increased  yields  of  ether  by  passing 
alcohol  vapour,  superheated  to  130°,  into  a  column  filled  with  pebbles,  among  which  the 
sulphuric  acid  is  circulated  or  sprayed;  for  100  kilos  of  ether  only  180  kilos  of  steam  is 
required  for  heating  instead  of  700  kilos  used  in  the  old  process.  From  the  top  of  this 
column  issue  the  ether  vapour  and  the  excess  of  alcohol  vapour,  the  latter  being  condensed 
in  a  superposed  rectifying  column  kept  at  a  convenient  temperature;  the  ether  vapour 
is  rectified  in  a  subsequent  column,  where  a  little  alcohol  is  condensed,  and  then  passes  to 
the  refrigerating  coils,  in  which  it  is  completely  condensed.  The  condensed  alcohol  is 
brought  continuously  to  the  desired  concentration  by  means  of  a  suitable  rectifying  column. 

P.  Fritzsche  (1912)  suggests  the  manufacture  of  ether  by  fixing  the  ethylene  of  oil-gas 
(see  p.  61)  by  means  of  sulphuric  acid,  the  resulting  ethylsulphuric  acid  being  diluted  and 
heated  to  give  ether  and  sulphuric  acid. 

USES  AND  PRODUCTION.  Ether  is  used  in  small  quantity  as  an  anaesthetic,  and  in 
large  quantities  in  the  manufacture  of  collodion  and  artificial  silk  (1000  kilos  of  silk  require 
about  5000  kilos  of  ether),  as  well  as  for  smokeless  powders  (Powder  B).1  It  serves  also 

1  Recovery  of  ether  from  the  air.  In  the  manufacture  of  smokeless  powders  and  especially 
of  powder  B  (see  later  :  Explosives),  enormous  quantities  of  ether,  mixed  with  alcohol,  are  used. 
In  the  Ferrania  (Savona)  works  of  the  Societa  Italiana  Prodotti  Esplodenti,  where  powder  B 


FIG.  180. 


232  ORGANIC    CHEMISTRY 

as  a  solvent  for  numerous  organic  compounds  in  dye  and  perfume  factories.  In  Ireland 
it  is  drunk  as  a  liqueur — a  refined  form  of  alcoholism. 

The  amount  of  ether  manufactured  in  Germany  in  1902  was  about  2000  tons,  without 
counting  that  now  made  in  large  quantities  for  the  production  of  artificial  silk  by  the 
Chardonnet-Lehner  process. 

In  Italy  large  amounts  of  ether  were  manufactured  prior  to  1910  when  the  artificial 
silk  works  used  the  Chardonnet  process.  During  the  European  War  it  was  made  for 
preparing  smokeless  powder  (Powder  B) ;  it  is  protected  by  a  Customs  duty  of  £72  per  ton. 
In  1907,  Gulinelli's  distillery  (Ferrara)  alone  produced  359  tons  of  ether.  Owing  to  the 
crisis  in  the  Italian  artificial  silk  industry,  the  production  had  fallen  considerably 
in  1910. 

Ether  exempt  from  duty  was  sold  in  Germany  before  the  war  at  £40  per  ton  if  its  sp.  gr. 
was  0-722,  whilst  the  price  of  the  pharmacopceial  product,  sp.  gr.  0-720,  was  £90.  Taxed 
ether,  distilled  over  sodium  and  chemically  pure,  cost  4s.  per  kilo.  In  1909,  ether  for 
artificial  silk  manufacture  cost  £2  11s.  per  hectolitre  in  Belgium  and  £2  14.s.  in  Austria. 
In  general  ether  costs  one  and  a  half  times  as  much  as  alcohol. 

TESTS  FOR  ETHER.  Ether  containing  water  or  alcohol  has  a  specific  gravity  between 
0-720  and  0-733.  When  20  c.c.  of  ether  is  shaken  with  5  c.c.  of  water,  the  latter  should 
not  assume  an  acid  reaction.  Ozone  or  hydrogen  peroxide  may  be  detected  by  means  of 
potassium  iodide  solution,  which  is  turned  brown  in  the  dark  in  the  course  of  an  hour. 
White  ignited  copper  sulphate  is  rendered  green  or  blue  by  aqueous  ether.  Eder  (1876) 
and  Dan  Tyrer  showed  that  cadmium  iodide  is  insoluble  in  absolutely  dry  ether,  0-64  per 
cent,  of  the  iodide  being  dissolved  for  each  0-1  per  cent,  of  water  present. 

In  a  mixture  of  alcohol  and  ether,  Fleischer  and  Frank  (1907)  determine  the  proportions 
of  the  two  components  by  shaking  10  c.c.  of  the  mixture  in  a  graduated  tube  with  5  c.c. 
of  benzene  and  6  c.c.  of  water :  the  increase  in  volume  of  the  water  shows  the  amount  of 
alcohol  and  that  of  the  benzene  the  amount  of  ether. 

Various  ^chlorinated  derivatives  of  ether  are  known. 

Ethyl  Peroxide,  C2H5  •  0  •  O  •  C2H5,  is  prepared  by  introducing  ethyl  groups  into 
hydrogen  peroxide  by  means  of  ethyl  sulphate;  it  is  a  liquid,  b.-pt.  65°,  difficultly  soluble 
in  water  and  very  readily  inflammable,  but  is  moderately  stable  towards  chemical 
reagents. 

In  1901  Baeyer  prepared  also  the  Hydrate  of  Ethyl  Peroxide,  C5H2O  •  OH,  as  a  colour- 
less liquid,  which  possesses  strong  oxidising  properties,  dissolves  in  water,  boils  at  95°, 
and  forms  barium  and  other  salts. 

is  made,  a  plant  capable  of  producing  20,000  kilos  of  ether  per  day  is  at  work.  In  some  of  the 
large  French  works  making  powder  B,  the  daily  consumption  of  ether  exceeds  100  tons,  although 
50  per  cent,  of  it  is  recovered.  The  recovery  of  the  ether  is  hence  a  problem  of  great  import- 
ance. The  air  drawn  from  the  galleries  or  chambers  where  the  powder  B  (which  contains  about 
35  per  cent,  of  ether  and  18  per  cent,  of  alcohol)  is  dried  contains  as  much  as  400  grams  of  ether 
and  alcohol  per  cubic  metre.  Part  of  this  air  is  passed  through  a  refrigerating  chamber  at 
—  15°  and  issues  with  only  20  to  30  grams  of  ether  per  cubic  metre ;  it  is  then  mixed  with  the 
portion  which  has  not  been  cooled  and  again  traverses  the  drying  galleries  or  chambers  at  40°, 
and  thus  becomes  saturated  again  with  alcohol  and  ether.  This  air  is  circulated  by  means  of 
fans  having  a  capacity  of  10,000  to  15,000  cu.  metres  per  hour;  the  part  which  is  cooled  con- 
stitutes only  one-sixth  or  one-tenth  of  the  whole  volume.  The  solvent  condensed  by  the  cooling 
contains  60  per  cent,  of  ether  and  40  per  cent,  of  alcohol.  After  this  treatment  the  powder  B 
still  contains  more  than  20  per  cent,  of  solvent  and  is  dried  completely  in  a  gentle  current  of 
air,  which  takes  up  less  than  35  grams  of  ether-alcohol  per  cubic  metre  and  is  usually  not  passed 
through  the  recovery  apparatus.  By  this  system  about  56  per  cent,  of  the  ether  and  36  per 
cent,  of  the  alcohol  used  are  recovered. 

According  to  another  system  the  ether  is  fixed  by  passing  the  air  through  concentrated 
sulphuric  acid,  which  is  afterwards  diluted  and  heated,  the  bulk  of  the  ether  being  thus  liberated 
(see  p.  229) ;  about  60  per  cent,  of  the  total  solvent  is  thus  recovered.  The  use  of  castor-oil 
in  place  of  sulphuric  acid  has  also  been'  suggested,  this  fixing  both  ether  and  alcohol  and 
subsequently  giving  them  up  in  good  yield. 

J.  H.  Bregeat  fixes  the  alcohol  and  ether  of  the  air  by  means  of  cresol  (see  later  :  Benzene 
derivatives),  b.-pt.  195°  to  205°,  which  absorbs  even  5  grams  of  these  compounds  per  cubic 
metre  of  air;  all  the  alcohol  and  ether  is  recovered  from  the  solution  by  heating  the  latter 
in  iron  vessels  at  125°  to  130°,  the  cresol  being  afterwards  cooled  and  used  again.  In  this  way 
92  to  95  per  cen"t.  of  the  alcohol  and  ether  is  recoverable,  the  cost  being  one-half  of  that  incurred 
when  sulphuric  acid  is  used  and  one-third  of  that  of  the  freezing  method. 


MERCAPTANS  233 

II.  THIO-ALCOHOLS   AND   THIO-ETHERS 

These  have  the  same  constitution  as  the  alcohols  and  ethers,  excepting 
that  the  oxygen  is  replaced  by  sulphur.  They  are  very  volatile  and  inflam- 
mable liquids,  almost  insoluble  in  water  and  having  repulsive  garlic-like  odours ; 
in  the  higher  members,  however,  the  odour  diminishes  and  the  solubility  in 
water  vanishes,  although  they  continue  to  be  soluble  in  alcohol  or  ether. 

(a)  THIO-ALCOHOLS  (or  Mercaptans  or  Thiols  or  Alkyl  Hydrosulphides), 
CnH2)i  +  1SH,  have  lower  boiling-points  than  the  corresponding  alcohols.     They 
are  feebly  acid  in  character  and  form  salts  called  Mercaptides,  e.  g.,  with  mer- 
curic oxide.     They  are  soluble  in  concentrated  alkali  solutions.     They  may  be 
regarded  as  hydrogen  sulphide  in  which  one  atom  of  hydrogen  is  replaced  by  an 
alkyl  radicle,  e.  g.,  ethanthiol  or  ordinary  Mercaptan,  C2H5SH.     As  acids  they 
are  monobasic,  and  salts  are  formed  with  metallic  sodium  or  potassium ;   the 
lead  salts  are  yellow  and  are  obtained  by  the  action  of  lead  acetate  in  alcoholic 
solution.     Nitric  acid  transforms  the  mercaptans  into  alkylsulphonic  acids  : 
C2H5SH  +  3O  =  C2H5  •  S03H. 

With  iodine,  the  salts  of  sodium,  etc.,  give  disulphides  : 

2C2H5SNa  +  I2  =  2NaI  +  (C2H5)2S2, 

which,  with  hydrogen,  give  mercaptans,  and  with  nitric  acid  disulpJioxides, 
(C2H5)2S202 ;  concentrated  sulphuric  acid  gives  disulphides  and  is  itself  reduced 
to  sulphur  dioxide. 

(b)  THIO-ETHERS   (or  Alkyl  Sulphides),  (CnH2rt  +  1)2S,  are  neutral,  readily 
volatile  liquids,  and  afford  a  good  illustration  of  the  variability  of  the  valency 
of  sulphur  (di-  to  hexa-valent). 

They  may  be  regarded  as  derived  from  hydrogen  sulphide  by  replacement 
of  the  two  hydrogen  atoms  by  alkyl  groups.  With  salts  they  form  double 
compounds,  e.  g.,  ethyl  sulphide  with  mercuric  chloride  gives  (C2H5)2S,  HgCl2. 
They  combine  with  halogens,  giving,  for  instance,  (C2H5)2SBr2,  whilst  when 
treated  with  dilute  nitric  acid  they  fix  an  atom-  of  oxygen,  yielding,  e.  g., 
(C2H5)2SO,  ethyl  sulphoxide :  with  more  energetic  oxidising  agents,  a  further 
oxygen  atom  is  taken  up  with  formation  of  sulphones,  e.  g.,  Diethylsulphone, 
(C2H5)2SO2.  With  hydrogen,  the  sulphoxides  give  sulphides,  but  the  sul- 
phides are  not  reduced.  They  combine  with  alkyl  haloids,  forming  sulphonium 
compounds,  e.  g.,  ethyl  iodide  and  ethyl  sulphide  give  Triethylsulphonium 
Iodide,  (C2H5)3SI,  which  reacts  like  metallic  iodides  with  silver  hydroxide, 
yielding  Triethylsulphonium  Hydroxide,  (C2H5)3S  *  OH. 

METHODS  OF  FORMATION.  They  are  obtained:  (1)  by  heating  alkyl  haloids 
or  salts  of  alkylsulphuric  acids  with  an  alcoholic  or  aqueous  solution  of  potassium  sul- 
phide or  hydrosulphide  :  C2H5Br  +  KSH  =  KBr  +  C2H5SH;  2C2H5Br  +  K2S  =  2KBr 
+  (C2H5)2S ;  2C2H5  •  SO4K  +  K2S  =  2K2S04  +  (C2H5)2S. 

(2)  By  the  action  of  phosphorus  pentasulphide,  P2S5>  on  ethers.  Mixed  sulphides 
also  may  be  obtained  by  these  and  various  other  methods. 

METHYL  HYDROSULPHIDE  (Methanthiol),  CH3  •  SH,  is  found  among  the  gases 
from  the  anaerobic  decomposition  of  proteins  (for  instance,  in  the  intestines  of  animals). 
It  is  a  nauseous  liquid,  lighter  than  water  and  boiling  at  6°. 

METHYL  SULPHIDE,  (CH3)2S,  is  a  liquid,  b.-pt.  37°,  having  a  disagreeable  ethereal 
odour. 

ETHYL  HYDROSULPHIDE  (Ethanthiol,  Ethylmercaptan,  or  Mercaptan), 
C2H5  •  SH,  is  a  liquid,  b.-pt.  36°,  having  a  repulsive  odour  and  is  used  for  the  preparation 
of  sulphonal.1  With  sodium  ethoxide  in  alcoholic  solution  it  gives  Sodium  Mercaptide, 
C2H5SNa,  in  white  crystals;  Mercuric  Mercaptide,  (C2H5S)2Hg,  has  also  been  obtained. 

1  SULPHONAL  is  an  important  anaesthetic  (see  p.  118)  and  is  obtained  by  saturating  an 
acetone  solution  of  ethylmercaptan  with  gaseous  hydrogen  chloride  or  by  treatment  with  zinc 
chloride,  the  mercaptol,  C(CH3)2  (SC2H5)2,  thus  formed  being  oxidised  by  potassium  perman- 
ganate to  form  sulphonal,  C(CH3)2  (S02C2H6)2,  which  crystallises  in  colourless,  odourless,  insipid 


234  ORGANIC    CHEMISTRY 

ETHYL  SULPHIDE,  (C2H5)2S,  is  a  liquid,  b.-pt.  92°,  insoluble  in  water,  and  forms 
a  crystalline  bromide,  (C2H5)2SBr2. 

ETHYL  DISULPHIDE  (Ethanodithioethane),  (C2H5)2S2,  boils  at  151°,  and  is 
obtained  by  the  action  of  iodine  on  mercaptan. 

ETHYL  SULPHOXIDE  (Ethanosulphoxy ethane),  (C2H5)2SO,  is  a  dense  liquid, 
soluble  in  water,  and  readily  reducible. 

ETHYLSULPHONE  (Ethanosulphonethane,  Diethylsulphone),  (C2H5)2S02,  boils 
unchanged  and  does  not  undergo  reduction. 

TRIMETHYLSULPHONIUM  IODIDE,  (CH3)3SI,  obtained  from  sulphur  and  methyl 
iodide,  forms  white  crystals  soluble  in  water  and  with  silver  hydroxide  gives  the  Hydroxide, 
(CH3)3SOH,  which  is  an  energetic  base  and  displaces  ammonia  from  its  salts. 

III.  ETHERS   OF   ALCOHOLS   WITH   INORGANIC   ACIDS 

Ethers  formed  from  an  alcohol  residue  and  an  acid  residue  are  termed 
Compound  Ethers  or  Esters.  We  shall  here  describe  those  derived  from 
mineral  acids  and  shall  consider  organic  acid  esters  more  in  detail  when  the 
acids  themselves  have  been  studied.  The  esters  may  be  regarded  as  derived 
either  from  acid  by  the  replacement  of  the  acid  hydrogen  by  an  alkyl  residue, 
as  with  the  salts,  or  from  alcon ols  by  replacement  of  the  hydroxylic  hydrogen 
by  an  acid  radicle  : 

HN03  .    .    .  KN03  .    .    .'C2H5-N03 

or    C2H5-OH  .    .    .   C2H5-0(N02)  .   .    .  C2H5  •  O(S03H) . 

Monobasic  acids  form  only  one  class  of  esters,  viz.,  normal  esters. 

Dibasic  acids  form  two  series  of  esters,  normal  and  acid  :  e.  g.,  C2H5HS04, 
acid  ester,  and  (C2H5)2SO4,  normal  ester. 

Tribasic  acids  give  three  kinds  of  esters  with  constitutions  analogous  to 
those  of  the  salts. 

The  Normal  Esters  are  neutral  liquids  of  agreeable  odour,  moderately 
volatile  and  insoluble  in  water. 

The  Acid  Esters  have  acid  reactions,  are  less  stable,  odourless,  soluble  in 
water,  and  volatile  without  decomposition. 

In  general,  these  esters  are  decomposed  by  alkali  or  water  at  a  high  tempera- 
ture (150°  to  180°),  the  components  being  regenerated;  this  change  is  known 
as  Saponification  :  C2H5N03  +  KOH  =  C2H5'OH  -f  KN03. 

FORMATION.  (1)  They  are  usually  formed  by  the  interaction  of  the 
components  (absolute  alcohol  -f-  acid),  the  water  which  gradually  forms  being 
fixed  and  the  resulting  ester  distilled.  With  some  acids,  the  corresponding 
salts  in  presence  of  concentrated  sulphuric  acid  at  100°  to  130°  are  taken, 
so  that  the  acid  is  obtained  in  the  nascent  state  and  the  ester  driven  off  as  it  is 
formed.  They  are  more  readily  obtainable  by  saturating  the  mixture  of 
alcohol  and  salt  with  gaseous  hydrogen  chloride. 

(2)  From  the  silver  salt  of  the  acid  and  an  alkyl  iodide  : 

Ag2S04  +  2C2H51  =  2AgI  +  S04(C2H5)2. 

(3)  From  the  alcohol  or  alkoxide  with  the  chloride  of  the  acid  : 

SOC12  +  2C2H5OH  =  2HC1  +  SO(OC2H5)2;   and 
POC13  +  3C2H5ONa  =  3NaCl  +  PO(OC2H5)3  (ethyl  phosphate). 

(4)  By  passing  the  vapours  of  the  acid  and  alcohol  together  over  a  catalyst 
as  much  as  50  per  cent,  of  the  ester  is  obtained. 

prisms,  m.-pt.  125°  to  126°,  boiling  unchanged  at  300°.  It  dissolves  slightly  in  water,  alcohol 
or  ether  in  the  cold,  but  is  readily  soluble  in  boiling  water  or  alcohol.  When  heated  in  a  tube 
with  powdered  wood  charcoal,  it  emits  the  repulsive  odour  of  mercaptan,  one-four  hundred 
millionth  of  a  milligram  of  which  is  detectable.  If  is  sold  at  24s.  per  kilo. 


VARIOUS    ESTERS  235 

1.  ESTERS  OF  SULPHURIC  ACID   AND  ALKYLSULPHURIC  ACIDS.     These 
are  generally  prepared  from  fuming  sulphuric  acid  and  alcohol,  or  from  silver  sulphate 
and  alkyl  iodide  or  from  alcohol  and  sulphuryl  chloride, 

S02C12  +  2C2H5OH  =  2HC1  +  S02(C2H5O)2; 

acid  esters  (alkylsulphuric  acids)  also  exist.     Tertiary  alcohols  do  not  form  these  esters. 

Ethyl  Sulphate,  (C2H5)2SO4,  is  an  oily  liquid  with  an  odour  of  mint  and  a  pronounced 
acid  character ;  it  boils  at  208°  and  is  easily  saponified,  even  by  boiling  with  water  alone. 
It  is  formed  by  heating  ethylsulphuric  acid  : 

2C2H5S04H  =  S04H2  +  S04(C2H5)2. 

Ethylsulphuric  Acid,  C2H5SO4H  —  (C2H50  •  S03H),  is  formed  as  an  initial  product 
in  the  manufacture  of  ether  (p.  228).  It  is  soluble  in  water  and  is  distinguished  from 
sulphuric  acid  by  the  solubility  of  its  calcium,  strontium,  barium,  and  lead  salts.  It 
gives  well  crystallised  salts,  the  potassium  salt  being  largely  used  for  preparing  ethyl 
derivatives,  e.  g.,  when  it  is  dry-distilled  with  potassium  bromide  : 

KBr  +  C2H6SO4K  =  S04K2  +  C2H5Br. 

2.  DERIVATIVES  OF  SULPHUROUS  ACID  :    (a)  Sulphurous  Esters  ;    (b)  Sul- 
phonic  Acids. 

(a)  Ethyl  Sulphite,  S03(C2H5)2,  and  ethylsulphurous  acid,  C2H5S03H.  The  latter 
is  known  also  in  the  form  of  salts  and  both  are  readily  saponified,  since  the  sulphur  is  not 
directly  united  with  carbon  :  CH3  •  CH2  •  0  •  S02H. 

(6)  Ethylsulphonic  Acid,  C2H5  •  SO3H,  is  obtained  by  the  reaction 

C2H5I  +  SO3Na2  =  Nal  +  C2H5S03Na; 

or  by  oxidising  the  thioalcohols  :    C2H5SH  +  O3  =  C2H5  •  S03H ;   or  thus  : 
2C2H5I  +  Ag2S03  =  2AgI  +  (C2H5)2S03  (ethyl  ethylsulphonate). 

Sulphonic  acid  compounds  are  not  saponifiable;  diethylsulphonic  acid  is  saponifiable  to 
the  extent  of  one-half,  since  in  the  sulphonic  acids  the  sulphur  is  united  with  carbon : 
CH3  •  CH2  •  S02  •  OH ;  the  presence  of  hydro xyl  is  shown  by  the  fact  that  with  PC15  it  forms 
C2H5  •  SO2CI,  which  with  hydrogen  gives  ethylsulphinic  acid,  C2H5SH02,  the  salts  of  the 
latter  reacting  with  alkyl  haloids  to  form  sulphones.  Sulphonic  acids  are  strong  acids  and 
give  salts  soluble  in  water. 

3.  ESTERS  OF  NITRIC  ACID.     These  are  explosive  if  heated  rapidly  and  undergo 
saponification  when  boiled  with  an  alkali.     Tin  and  hydrochloric  acid  reduce  them,  giving 
Hydroxylamine,  NH2OH,  the  nitrogen  being  separated  from  the  radicle  as  in  saponification. 

METHYL  NITRATE,  CH3O-NO2,  obtained  by  treating  a  mixture  of  methyl  alcohol 
and  potassium  nitrate  with  concentrated  sulphuric  acid,  is  a  colourless  oil  of  unpleasant 
odour  and  sweet  taste.  It  boils  at  66°,  has  the  sp.  gr.  1-182  at  22°,  is  soluble  in  alcohol 
or  ether,  but  insoluble  in  water,  and  is  explosive  and  dangerous  to  handle. 

Ethyl  Nitrate  :  C2H5O  •  NO2,  a  liquid  boiling  at  86°,  is  obtained  from  absolute  alcohol 
and  concentrated  nitric  acid,  the  formation  of  the  dangerous  nitrous  products  being  prevented 
by  addition  of  a  little  urea. 

4.  ESTERS  OF  NITROUS  ACID.     These  are  easily  obtained  by  passing  nitrogen 
trioxide  (N203)  into  the  alcohols,  or  by  treating  the  latter  with  alkali  nitrites  and  sulphuric 
acid.    They  are  reduced  by  nascent  hydrogen,  giving  alcohol  and  ammonia. 

Ethyl  Nitrite,  C2H5O  •  NO,  was  at  one  time  called  nitric  ether.  Dissolved  in  alcohol,  it 
bears  the  name  Spiritus  cetheris  nitrosi,  and  is  used  to  modify  the  taste  of  various  substances. 
It  is  also  used  for  preparing  diazo-compounds. 

5.  NITRO-DERIVATIVES    OF    THE    HYDROCARBONS.      These   are    isameric 
with  nitrous  esters,  but  they  boil  at  higher  temperatures  than  the  latter  and  are  distin- 
guished from  them  by  being  non-saponifiable  and  by  giving  organic  amino-compounds  on 
reduction,  as  long  as  the  nitrogen  is  not  severed  from  the  organic  radical : 

CH3  •  N02  (nitromethane)  +  3H2  =  2H2O  +  CH3  •  NH2. 
They  are  formed  by  treating  alkyl  iodides  with  silver  nitrite  : 
CH3I  +  AgN02  •=  Agl  +  CH3  •  N02; 


236  ORGANIC    CHEMISTRY 

with  the  higher  members  of  the  series,  the  nitrous  esters  are  formed  at  the  same  time  and 
may  be  separated  by  distillation.  Of  the  various  methods  of  formation,  mention  may 
be  made  of  that  based  on  the  action  of  dilute  nitric  acid,  in  the  hot  and  under  pressure, 
on  the  paraffins  : 

C6H14  +  HN03  =  C6H13  -  N02  +  H2O. 

Hexane  Nitrohexane 

Concentrated  nitric  acid  does  not  give  nitro-compounds  with  the  paraffins,  but  with 
aromatic  hydrocarbons  it  reacts  readily. 

The  difference  in  constitution  between  nitro-derivatives,  e.  g.,  H3C  •  N02,  and  nitrous 
•esters,  e.  g.,  H3C  •  0'-  N  :  O,  explains  their  different  relations  as  regards  saponification. 

This  also  confirms  the  hypothetical  constitution  of  nitrous  acid,  0 :  N  •  OH.  The 
hydrogen  of  the  carbon  atom  united  to  nitrogen  may  be  partially  substituted  by  metals  or 
bromine,  since  it  has  acquired  acid  characters — for  instance,  NaCH2  •  N02 — but  the  acidify- 
ing influence  of  the  nitro-group  is  not  extended  to  the  hydrogens  of  the  other  carbon  atoms. 

These  nitroparaffins  react  with  nitrous  acid  differently  according  as  they  are  primary, 
secondary,  or  tertiary : 

,H2  N  •  OH 

(a)  Nitroethane,    CH3  -  Cf  +  N02H  =  H20  +  CH3  -  Cf  i.  e.,  ethyl- 

XN02  XN02 

nitric  acid,  salts  of  which  are  red. 

CHS.         ,H  CH3  N=0 

(6)  Secondary    Nitropropane,  XC(          +  N02H  -  H20  + 

CH/     XN02  C 

propylpseudonitrole,  which  forms  blue  salts. 

(c)  Tertiary  derivatives  give  no  reaction. 

These  reactions  serve  well  to  distinguish  primary,  secondary,  and  tertiary  alcohols. 

Nitroethane  may  be  used  in  the  manufacture  of  explosives  to  lower  the  freezing-point 
of  nitroglycerine. 

CHLOROPICRIN,  CC13 .  NO2,  sp.  gr.  1-692,  boils  at  112°,  and  is  formed  by  the 
simultaneous  action  of  nitric  acid  and  chlorine  on  various  organic  compounds. 

It  is  also  obtained  when  a  mixture  of  60  grams  of  picric  acid,  7  kilos  of  water  and  1-5 
kilo  of  calcium  hypochlorite  is  heated  by  direct  steam,  the  oily  chloropicrin  which  distils 
over  being  washed  with  very  dilute  soda  solution,  decanted,  dried,  and  distilled.  It  is 
soluble  in  alcohol,  ether,  or  benzene  and  slightly  so  in  water.  It  is  a  powerful  and  irritating 
lachrymatory  and  was  largely  used  during  the  European  War.1  When  superheated  it 

1  CHEMISTRY  AND  THE  WAR.  Among  the  poisonous  gases  and  liquids  used  during 
the  war  are  the  following  :  phosgene,  chlorine,  bromine,  cyanogen  bromide,  bromoacetone, 
aromatic  arsines,  nitrous  vapours,  acrolei'n,  allyl  isothiocyanate,  phosphorus,  tin  and  arsenic 
chlorides,  benzyl  bromide,  etc.  The  terrible  mustard  gas  or  yprite  consists  of  &&'-dichloroethyl 
sulphide,  S(CH2  •  CH2C1)2,  which  is  a  yellowish,  neutral,  odourless  oil  of  sp.  gr.  1-27,  m.-pt.  7°, 
b.-pt.  217°  to  219°  (decomposing  slightly).  It  is  almost  insoluble  in  water,  has  a  high  vapour 
pressure,  and  produces  extraordinarily  lachrymatory  and  poisonous  effects,  even  when  brought 
into  contact  with  the  skin ;  it  easily  penetrates  clothing.  It  was  first  used  by  the  Germans 
against  the  British  at  Ypres  on  July  20,  1917,  and  afterwards  at  Nieuport  and  Armentieres; 
on  these  two  cities  as  many  as  50,000  mustard  gas  shells  per  day  were  dropped  for  several  days. 
In  Germany  50  to  60  tons  were  made  per  day,  in  France  20  tons,  and  in  America  40  tons.  It 
is  slowly  saponified  by  hot  alkali,  and  dissolves  in  alcohol,  ether,  benzine,  etc. ;  with  halogens 
it  yields  substitution  products.  By  oxidising  agents  (hydrogen  peroxide,  permanganate,  ozone, 
calcium  hypochlorite,  etc.)  it  is  easily  transformed  into  harmless  compounds,  SO(CH2  •  CH2C1)2 
and  S02(CH2-CH2C1)2. 

In  Germany  mustard  gas  was  made  by  heating  glycol  chlorohydrin  on  a  water-bath  with 
concentrated  aqueous  potassium  sulphide  and  then  evaporating  and  taking  up  the  residue  in 
absolute  alcohol  to  get  rid  of  sodium  chloride.  The  syrupy  residue  left  after  expulsion  of  the 
alcohol  was  treated  with  phosphorus  pentachloride,  the  mass  being  afterwards  poured  on  to 
ice  and  the  oil  separated.  In  England  (and  America)  mustard  gas  was  made  by  the  interaction 
of  ethylene  and  sulphur  chloride  :  2C2H4  +  SCI.  =  S(CH2  •  CH2C1)2.  The  ethylene  was 
obtained  in  85  per  cent,  purity  by  passing  alcohol  vapour  over  lumps  of  kaolin  heated  at  500°  to 
600°  in  retorts,  titanium  oxide  being  used  as  catalyst;  in  England  increased  yields  were  obtained 
by  using  coke  impregnated  with  phosphoric  acid  in  place  of  kaolin  and  titanium.  The  reaction 
between  C2H4  and  SC12  (or  S2C12)  takes  place  at  30°  to  35°  and  is  regulated  by  cooling.  To  render 
the  mustard  gas  more  injurious  and  more  volatile,  it  was  mixed  with  carbon  tetrachloride  or 
chlorobenzene.  Partial  protection  was  afforded  by  rubber  clothing  and  by  bathing  with 
permanganate. ' 

Two  mustard  gas  works  were  under  construction  in  Italy  when  the  Armistice  was  proclaimed. 


NITRILES        .  237 

explodes.  When  its  solution  or  aqueous  emulsion  is  reduced  with  iron  turnings  and  a 
little  acetic  acid  (other  acids  are  unsuitable),  it  is  transformed  into  methylamine.  With 
stannous  chloride  it  gives  cyanogen  chloride,  while  when  heated  at  100°  with  aqueous 
ammonia  it  yields  guanidine. 

NITROMETHANE,  CH3  •  N02,  is  obtained  from  methyl  iodide  and  silver  nitrate  or, 
better  (but  still  in  poor  yield)  by  distilling  an  aqueous  solution  of  potassium  chloroacetate 
(1  part)  and  potassium  nitrite  (3  parts),  the  distillate  being  separated  from  the  water, 
dried  with  lime  and  rectified. 

It  forms  an  oil  of  ethereal  odour  and  is  denser  than  water,  in  which  it  is  slightly  soluble ; 
it  bpils  at  101°  and  burns  with  a  pale  flame.  When  reduced  with  iron  and  acetic  acid  it 
gives  methylamine,  while  with  HC1  at  150°  it  yields  hydroxylamine  and  formic  acid,  and 
with  hot,  fuming  sulphuric  acid,  carbon  monoxide  and  hydroxylamine  sulphate. 

One  of  its  hydrogen  atoms  is  readily  replaceable  by  metals;  with  alcoholic  potash 
solution  it  forms  crystals  of  CH2K  •  NO2  +  C2H5  •  OH,  the  alcohol  being  expelled  in  a 
sulphuric  acid  desiccator.  The  mercury  salt  is  explosive. 

It  is  a  good  solvent  for  smokeless  powders  and  in  the  proportion  of  10  per  cent,  lowers 
the  freezing-point  of  nitroglycerine  to  — 10°. 

DINITROMETHANE,  CH2(N02)2,  forms  yellow  crystals  exploding  at  200°.  Its 
potassium  salt,  CHK(N02)2,  is  obtained  when  hydrogen  sulphide  is  passed  into  an 
ammoniacal  solution  of  potassium  bromodinitromethane. 

TRINITROMETHANE  (Nitroform),  CH(N02)3,  is  obtained  as  ammonium  salt  when 
trinitroacetonitrile  is  heated  with  water  :  C(NO2)3  •  CN  +  2H20  =  C02  +  C(N02)3  •  NH4 . 
It  forms  white  crystals,  m.-pt.  15°,  and  at  100°  decomposes  with  explosion.  It  dissolves 
in  water  to  a  yellow  solution  and  acts  as  a  strong  acid;  on  reduction  with  tin  and 
hydrochloric  acid  it  gives  hydrocyanic  acid. 

TETRANITROMETHANE,  C(N02)4,  obtained  by  heating  nitroform  with  concen- 
trated sulphuric  and  fuming  nitric  acids,  forms  'white  crystals,  m.-pt.  13°,  and  boils 
unchanged  at  126° ;  it  is  insoluble  in  water,  but  dissolves  in  alcohol  or  ether.  It  is  non- 
inflammable,  has  no  acid  reaction,  and,  mixed  with  petroleum,  is  used  as  an  explosive 
of  the  Sprengel  type  (see  Explosives).  R.  Schenck  (Ger.  Pat.  211,198,  1908)  prepared 
tetranitromethane  in  various  ways. 

NITROETHANE,  C2H5-N02,  has  m.-pt.  113°,  and  nitropropane,  m.-pt.  130°.  Dini- 
troethane  has  b.-pt.  185°  to  186°;  trinitroethane,  CH3-C(N02)3,  m.-pt.  56°,  is  obtained 
from  methyl  iodide  and  the  silver  salt  of  trinitromethane.  Tetranitroethane  is 
obtained  as  dipotassium  derivative  by  treating  bromopicrin  with  potassium  cyanide; 
it  is  readily  decomposed,  even  by  cold  dilute  sulphuric  acid.  Hexanitroethane, 
C(N02)3'  C(N02)3,  was  prepared  in  1914  by  W.  Will  as  an  explosive  by  treating  the  pure 
potassium  salt  of  tetranitroethane  at  a  temperature  of  3°  to  5°  with  concentrated 
sulphuric  acid  and  then  with  nitric-sulphuric  acid,  the  mass  being  finally  heated  for  ten 
minutes  at  60°  to  70°,  and  then  cooled  and  poured  into  water;  when  freed  from  acid  it  is 
obtained  from  ether  in  white  crystals  which  have  a  slight  camphor  smell,  melt  at  142°, 
and  give  a  yellow  solution  in  benzene  or  toluene;  with  afcoholic  soda  it  gives  tetrani- 
troethane, while  under  prolonged  heating  at  75°  it  forms  yellow  vapours.  It  is  moderately 
resistant  to  shock  and  friction,  and  when  mixed  with  hydrogenated  organic  compounds 
yields  explosives  of  practical  use  although  of  limited  stability. 

Various  esters  of  hyponitrous,  phosphoric,  boric,  silicic  acids,  etc.,  are  known. 

DERIVATIVES   OF   HYDROCYANIC  ACID 
A.  NITRILES.         B.  ISONITRILES 

These  compounds  are  formed  by  the  substitution  of  the  hydrogen  of  hydrocyanic  acid 
by  an  alkyl  radical,  but  they  are  not  true  esters,  as  they  do  not  give  the  acid  and  alcohol 
again  on  hydrolysis. 

A.  NITRILES  (or  Alkyl  Cyanides),  are  either  liquid  or  solid,  and  have  a 
pleasant,  faintly  garlic-like,  ethereal  odour.  They  are  lighter  than  water,  in 
which  the  first  terms  are  soluble  without  undergoing  change.  They  boil  at 
about  the  same  temperatures  as  the  corresponding  alcohols. 


238  ORGANIC    CHEMISTRY 

PREPARATION.  1.  They  are  obtained  by  distilling  a  potassium  alkyl- 
sulphate  with  potassium  cyanide  or  with  anhydrous  potassium  ferrocyam'de, 
or  by  heating  the  cyanide  at  180°  with  methyl  iodide  : 

CH3I  +  KCN  =  KI  -f  CH3  •  CN  (methyl  cyanide  or  acetonitrile) . 

2.  Distillation   of    ammonium    salts   of    monobasic    acids    yields   amido- 
compounds  which,  with  a  dehydrating  agent  (P205,  P2S5  or  PC15),  give  nitriles  : 

(a)  CH3  ;  COOH  +  NH3  =  H20  +  CH3  •  CO  •  NH2 ; 

Acetic  acid  Acetamide 

(6)  CH3  •  CO  •  NH2  -  H20  =  CH3  •  CN. 

Acetonitri'.e  or 
Methyl  cyanide. 

3.  The  higher  nitriles  are  formed  from  the  acid-amides  containing  one 
more  carbon  atom  or  from  the  primary  amine  containing  the  same  number  of 
carbon  atoms,  by  treatment  with  sodium  hydroxide  and  bromine ;   or  from  the 
aldehydes  which,  with  hydrocyanic  acid,  give  the  nitriles  of  higher  acids,  the 
so-called  cyanohydrins  or  hydroxynitriles,  liquid  compounds  easily  saponified 
with  regeneration  of  the  aldehyde  : 

,0  /OH 

CH3  •  Cf      +  HCN  =  CH3  •  CH< 

XH  XCN' 

Acetaldehyde  Ethylidenecyanohydrin 

PROPERTIES.  When  boiled  with  alkali  or  acid,  or  treated  with  super- 
heated steam,  nitriles  give  ammonia  and  an  acid,  from  which  products  they 
may  also  be  formed  : 

(a)  CH3CN  -f  H2O  =  CH3  •  CO  •  NH2  (aeetamide) ; 
(6)  CH3  •  CO  •  NH2  +  H20  =  CH3  •  CO  •  OH  +  NH3. 

This  reaction  is  of  importance  for  the  synthesis  of  organic  acids  since, 
starting  from  a  given  alcohol  and  transforming  it  into  iodide  and  then  into 
nitrile,  an  acid  of  the  saturated  series  containing  an  extra  carbon  atom  is 
obtained. 

If  the  cyanide  is  treated  with  hydrogen  sulphide  instead  of  water, 
thiocetamide,  CH3  •  CS  •  NH2,  is  obtained.  With  hydrochloric  acid,  the  nitriles 
form  chloramides  or  chlorimides,  whilst  with  ammoniacal  bases  they  give 
amidines  (see  later).  Nascent  hydrogen  converts  them  into  amines  :  CH3*CN 
+  2H2  =  CH3  •  CH2  •  NH2  (ethylamine).  By  potassium  or  by  gaseous  hydrogen 
chloride  the  nitriles  are  polymerised. 

ACETONITRILE  (or  Methyl  Cyanide),  CH3  .  CN,  is  found  among  the  products 
of  the  distillation  of  beetroot  molasses  and  of  tar.  It  is  soluble  in  water  and 
boils  at  82°. 

B.  ISONITRILES  (Isocyanides  or  Carbylamines)  are  colourless  liquids 
which  have  a  faint  alkaline  reaction  and  boil  at  rather  lower  temperatures  than 
the  corresponding  nitriles.  They  are  insoluble  in  water,  but  dissolve  in  alcohol 
or  ether.  They  have  repellent  odours  and  are  poisonous.  They  are  obtained 
by  the  interaction  of  alkyl  iodides  with  silver  cyanide  (whilst  with  potassium 
cyanide  the  nitriles  are  obtained)  : 

C2H5I  +  AgCN  =  Agl  +  C2H5  •  NO ;    ' 

they  are  also  formed  by  treating  the  primary  amines  with  chloroform  and 
alcoholic  potash  (see  p.  120);   also  later  under  Amines). 

Although  they  are  stable  towards  alkalis,  the  isonitriles  are  readily  decom- 
posed by  water,  giving  formic  acid  and  the  corresponding  amino-base  containing 
one  carbon  atom  less  than  the  isonitrile  : 

CH3  •  NC  +  2H20  =  H-COOH  +  CH3  •  NH2. 


AMINES  239 

From  the  nitrites  they  are  distinguished  also  by  the  different  additive 
compounds  which  they  form  with  halogens,  hydrogen  chloride,  hydrogen 
sulphide,  etc.  At  high  temperatures  certain  isonitriles  change  into  nitriles. 

CONSTITUTION  OF  THE  NITRILES  AND  ISONITRILES.  The  nitriles  have  the 
carbon  atom  of  the  cyanogen  group  attached  to  the  alkyl  radicle  and  when  they  are  hydro- 
lysed  only  the  nitrogen  is  removed  as  ammonia.  Acetonitrile  would  hence  have  the 
constitution,  CH3  —  C  =  N. 

The  isonitriles,  on  the  other  hand,  readily  form  amino-bases  with  loss  of  an  atom  of 
carbon — that  of  the  cyanogen  group — the  nitrogen  remaining  with  the  radicle.  Methyl 
isocyanide  or  methylcarbylamine  would  hence  have  the  formula  CH3  —  N  =  C. 

IV.  NITROGENATED   BASIC   ALKYL  COMPOUNDS    (AMINES) 

If  one  or  more  of  the  hydrogen  atoms  of  the  ammonia  molecule  is  replaced 
by  one  or  more  alky]  radicles,  substances  called  Amines  are  formed;  these 
have  a  basic  character,  which  is  in  some  cases  more  marked  than  that  of 
ammonia  itself  (in  the  dissociation  of  compounds  of  the  ammonia  type,  free 
anions,  OH',  are  formed).  They  were  discovered  by  Wurtz  in  1848,  and  were 
studied  systematically  by  A.  W.  Hofmann  in  1850-1851.  To  ammonia  they 
present  other  chemical  analogies.  They  have  disagreeable  ammoniacal  odours ; 
with  mineral  acids  they  form  white,  crystalline,  deliquescent  salts  which  are 
extremely  soluble  in  water  and  have  a  basic  nature,  the  nitrogen  then  becom- 
ing pentavalent ;  for  the  first  members  of  the  series  the  electrical  conductivity 
is  very  high,  higher  indeed  than  that  of  ammonia,  since  N/100  solutions  are 
almost  completely  dissociated.  . 

Like  ammonia,  they  give,  with  platinum  chloride,  crystalline  platini- 
chlorides,  e.  g.,  methylamine  platinichloride,  (NH2  •  CH3,  HCl)2PtCl4;  they  also 
form  double  salts  with  gold  chloride,  NH2  •  C2H5,  HC1,  AuCl3.  They  precipitate 
heavy  metals  from  solutions  of  their  salts,  and,  in  excess,  sometimes  redis- 
solve  them.  The  first  terms  are  gases,  after  which  come  unpleasant  smelling 
liquids  soluble  in  water.  The  higher  members  are  odourless  and  insoluble  in, 
and  lighter  than,  water ;  they  are  soluble  in  alcohol  and  in  ether. 

The  ammonia  derivatives  are  deliquescent  solids,  and  in  their  behaviour 
greatly  resemble  potassium  hydroxide,  etc.  According  as  they  contain  one 
or  more  alkyl  radicals,  these  bases  are  called  primary  or  aminic,  secondary  or 
iminic,  tertiary  or  nitrilic,  quaternary  or  ammoniacal. 

PROCESSES  OF  FORMATION,  (a)  By  heating  an  alkyl  halogen  com- 
pound with  ammonia  : 

(1)  NH3  +  CnH2n+1I  =  HI  +  aH2B+1NH2;  the  halogen  hydracid  formed 
unites    with    the    ammonia   and  with    the    amine,    converting   these    partly 
into   the   corresponding   salts ;    distillation   with   potassium   hydroxide   then 
gives  :   KI  -f  H20  +  the  free  base,  CnH2n  +  1  •  NH2.     The  latter,  which  is  partly 
free  before  treatment  with  potash,  may  in  its  turn  react  with  a  second  molecule 
of  the  alkyl  halogen  compound,  giving  a  secondary  amine ; 

(2)  CnH2n+1  -NH2  +  CBH2B+1I  =  (CnH2B+1)2NH,  HI;   the  free  base,  which 
may  be  liberated  by  distilling  with  KOH,  reacts  with  a  third  molecule  of  the 
alkyl  halogen  compound,  yielding  a  tertiary  amine ; 

(3)  (CnH2n+1)2NH  +  CnH2n  +  1I=(CBH2n+1)3N,  HI.     Finally,  the  tertiary 
base,  which  remains  free  or  may  be  liberated,  reacts  with  a  fourth  molecule 
of  the  halogen  derivative,  giving  the  salt  of  the  quaternary  base ; 

(4)  (CnH2n  +  1)3N  +  CBH2B  +  1I  =  (CBH2n+1)4NI,  which  is  no  longer  a  crystal- 
line  ammonia  base  and  is  not  decomposed  by  potassium  hydroxide,  being 
more  energetic  than  the  latter;    the  hydrogen  iodide  formed  unites   with 
the  amines  if  such  are  still  present.     When  heated,  the  iodide  of  the  quaternary 
base  is  converted  back  into  the  tertiary  base  and  alkyl  iodide,  whilst  with 


240  ORGANIC    CHEMISTRY 

silver  hydroxide  it  gives  the  corresponding  solid  alkylammonium  hydroxide. 
In  this  general  reaction,  the  four  bases  are  always  formed  together,  although 
more  of  one  or  another  is  obtained  according  to  the  nature  of  the  alkyl  group, 
the  temperature,  the  duration  of  the  reaction,  and  the  quantity  of  ammonia 
present. 

The  separation  of  the  bases  in  this  mixture  is  not  easy,  and  when  these  are 
present  as  salts,  distillation  with  potassium  hydroxide  yields  the  primary, 
secondary,  and  tertiary  amines,  whilst  the  quaternary  ammonium  compound 
remains  unchanged.  The  three  bases  or  the  corresponding  salts  are  separated 
partly  by  crystallisation  or  by  fractional  distillation,  or,  better,  by  means  of 
ethyl  oxalate,  C202(C2H50)2,  which  gives  solid  or  liquid  oxamides  [e.  g.,  solid 
dimethyloxamide,  C202(NH'  CH3)2  and  the  ethyl  ester  of  dimethyloxaminic  acid, 
C2H2(OC2H5)  •  N(CH3)2,  which  boils  at  243°  and  is  soluble  in  water,  alcohol 
or  ether]. 

Amines  may  also  be  prepared  by  the  following  reactions  : 
(6)  By  the  action  of  potassium  hydroxide  on  alkyl  isocyanates,  e.  g.,  ethyl 
isocyanate,  C2H5NCO  +  2KOH  =  K2C03  +  C2H5  •  NH2 ; 

(c)  By  reducing  nitro-compounds,  nitrites,   oximes,   or  hydrazones  with 
nascent  hydrogen. 

(d)  Primary  amines  may  be  obtained  by  heating  the  ethylnaphthylamines 
with  caustic  soda,  and  secondary  amines  in  the  same  way  from  nitrosodialkyl- 
anilines. 

PROPERTIES.  The  amines  do  not  undergo  hydrolysis  and  are  resistant 
to  the  action  of  acids,  alkalis,  and,  to  some  extent,  oxidising  agents.  The 
hydrogen  combined  with  the  nitrogen  of  amines  may  be  replaced  not  only  by 
alkyl  groups  (see  above],  but  also  by  acid  radicals  (e.  g.,  by  acetyl,  CH3-  CO') 
and  mixed  amines  with  alkyl  and  acidic  groups  may  also  be  obtained.  A 
characteristic  and  sensitive  reaction  of  the  primary  .amines  is  that  with 
chloroform  in  presence  of  alkali,  which  gives  rise  to  the  unpleasant-smelling 
isonitriles  :  CHC13  +  CH3  •  NH2  +  3KOH  =  CH3  •  NC  +  3KC1  +  3H20.  In 
alcoholic  solution  the  primary  and  secondary  bases  form,  with  carbon  disulphide, 
derivatives  of  thiocarbaminic  acid,  and  only  when  these  are  derived  from  the 
primary  bases  can  isothiocyanates  be  obtained.  It  is  easier  to  distinguish 
(and  separate)  primary,  secondary,  and  tertiary  amines  by  their  reactions 
with  nitrous  acid.  When  a  hydrochloric  acid  solution  of  the  mixture  is  treated 
with  a  concentrated  solution  of  sodium  nitrite,  the  primary  amine  yields  the 
corresponding  alcohol  (soluble  in  water),  with  evolution  of  nitrogen  : 

CnH2n+1NH2  +  NOOH  =  H20  +  N2  +  CnH2n+1OH. 

The  Secondary  amines  give  oily  nitrosamines,  almost  insoluble  in  water  : 
(CBH2n+1)2NH  +  NOOH  =  H20  +  (CnH2n+1)2N  •  NO  ;  with  feeble  reducing 
agents,  the  nitrosamine  is  transformed  into  a  hydrazine,  whilst  with  more 
energetic  reducing  agents  or  with  concentrated  hydrochloric  acid  the  secondary 
amine  is  regenerated,  showing  that  the  nitrous  residue  NO  is  joined  to  the 
iminic  nitrogen  and  not  to  the  carbon.  The  tertiary  amine  does  not  react  with 
nitrous  acid  and  is  hence  left  unchanged  in  the  solution,  from  which  it  may 
be  obtained  by  distillation  in  presence  of  caustic  soda. 

Finally,  the  three  classes  of  amines  may  be  distinguished  by  the  quantities 
of  methyl  iodide  with  which  they  react  to  produce  the  final  quaternary  base 
(see  preceding  page),  with  generation  of  greater  or  less  quantities  of  ionisable 
compounds  (titratable  HI). 

METHYLAMINE,  CH3  .  NH2,  is  found  ready  formed  in  certain  plants,  e.  g.,  in  the  dog- 
mercury  weed  (Mercurialis  perennis).  It  is  formed  in  the  distillation  of  wood  and  occurs 
in  beetroot  and  bone  residues  and  in  herring  brine.  It  is  prepared  from  methyl  chloride 
and  ammonia,  the  resulting  hydrochloride  being  separated  from  the  ammonium  chloride 


AMINES  241 

by  dissolving  the  former  in  a  little  water  (the  ammonium  chloride  is  less  soluble),  filtering 
by  suction  and  crystallising  the  filtrate  with  the  help  of  ammonia ;  the  secondary  amine 
formed  at  the  same  time  is  separated  as  nitroso-deiivative,  which  with  concentrated 
hydrochloric  acid  regenerates  the  base.  Plochl  prepares  methylamine  by  heating  a  mixture 
of  -formaldehyde  with  one-half  of  its  weight  of  ammonium  chloride.  It  is  a  gas  like 
ammonia  (but,  unlike  this,  burns  in  the  air)  and  precipitates  various  metallic  salts,  but, 
when  added  in  excess,  does  not  dissolve  nickel  and  cobalt  hydroxides ;  it  is  more  highly 
basic  and  more  soluble  in  water  (1  vol.  dissolves  1150  vols.  at  12-5°  and  959  vols.  at  25°) 
than  ammonia,  and  has  a  strong  odour  of  ammonia  and  rotten  fish.  It  becomes  liquid 
at  —  7°  and  at  —  11°  has  the  sp.  gr.  -0699.  It  is  formed  by  the  action  of  NaOH  and  Br 
on  acetamide,  and  also  by  the  reduction  of  chloropicrin  (see  p.  236).  Its  hydrochloride, 
CH3-NH2,HC1,  m.-pt.  225°,  is  a  crystalline,  deliquescent  substance  extremely  soluble  in 
alcohol.  With  aluminium  sulphate  its  sulphate  forms  an  alum  containing  24H20. 

DIMETHYLAMINE,  (CH3)2NH,  is  a  liquid  boiling  at  +  7°,  and  is  formed,  together 
with  acetic  acid,  in  the  distillation  of  wood. 

TRIMETHYLAMINE,  (CH3)3N,  is  a  gas  which  liquefies  at+  3°,  and  has  an  intense 
odour  of  rotten  fish.  It  is  found  in  various  plants  (Arnica  montana,  shoots  of  the  pear- 
tree,  etc. ),  and  in  herring  brine.  It  is  formed  by  the  decomposition  of  betaine  during  the 
distillation  of  beetroot  molasses  (p.  117). 

ETHYLAMINE,  C2H5  •  NH2,  may  be  prepared  as  follows :  30  parts  of  ethyl  alcohol 
are  saturated  in  the  cold  with  ammonia  and  the  liquid  heated  in  an  autoclave  at  about 
55°  with  8  parts  of  liquid  ammonia  and  10  parts  of  ethyl  chloride.  When  the  vigorous 
phase  of  the  reaction  is  at  an  end,  the  water-bath  surrounding  the  autoclave  is  brought  to 
boiling;  which  is  maintained  for  four  to  five  hours.  After  cooling,  the  excess  of  ammonia 
is  allowed  to  escape  and  is  used  to  saturate  the  alcohol  for  a  succeeding  operation.  The 
residue  in  the  autoclave  is  neutralised  with  hydrochloric  or  sulphuric  acid  and  the  salts 
separating  on  concentration  filtered  off  by  suction,  dried  and  extracted  with  alcohol  (which 
does  not  dissolve  the  mineral  salts).  After  evaporation  of  the  alcohol,  the  mixed  bases  are 
liberated  by  means  of  alkali  and  are  fractionated  in  a  column  4  metres  in  height.  The 
bulk  of  the  product  is  diethylamine,  the  ethylamine  remaining  in  solution  at  a  concentration 
of  15  to  20  per  cent. 

DIETHYLAMINE  (and,  similarly,  dimethylamine)  is  now  often  prepared  by  decom- 
posing paranitrosodiethylanil'ne  (as  hydrochloride)  with  boiling  5  per  cent,  caustic  soda 
solution  (in  the  proportion  of  1  :  20),  the  base  distilling  over  being  dissolved  in  hydrochloric 
acid.  The  yield  is  almost  theoretical,  and  the  paranitrosophenol  remaining  in  the  yellow 
solution  may  be  used  for  making  para-aminophenol. 

ETHYLAMINE  is  a  liquid,  b.-pt.  +  19°,  and  smells  strongly  of  ammonia,  which  it 
surpasses  in  basicity.  It  dissolves  very  readily  in  water  with  generation  of  heat.  It 
dissolves  aluminium  hydroxide  (like  methylamine,  but  unlike  ammonia)  and  to  a  small 
extent  cupric  hydroxide,  but  not  ferric  or  cadmium  hydroxide. 

DIETHYLAMINE,  (C2H5)2NH,  is  a  liquid,  b.-pt.  56°,  and  does  not  dissolve  zinc 
hydroxide. 

TRIETHYLAMINE,  (C2H5)3N,  is  an  oily  liquid  which  precipitates  metals  from  their 
salts,  but  does  not  redissolve  the  precipitates.  It  has  a  strongly  alkaline  reaction  and  boils 
at  89°.  It  is  extremely  soluble  in  cold  water,  but  above  20°  it  becomes  completely 
insoluble,  separating  from  the  water  in  an  oily  layer. 

A  group  of  nitrogen  compounds  which  may  be  considered  as  formed  by  the  condensa- 
tion of  ammonia  (hydrazine,  azoimide,  Tiydroxylamine,  etc.)  has  been  already  mentioned  in 
Vol.  I.,  p.  376.  The  alkyl  derivatives  of  hydroxylamine,  NH2  •  OH,  are  divided  into  two 
groups  :  a-alkylhydroxylamines,  in  which  the  alkyl  replaces  the  hydroxylic  hydrogen, 
NH.yOR,  and  which  hence  have  an  ether  character  and  do  not  reduce  Fehling's  solution; 
and  (3-alkylhydroxylamines,  in  which  the  alkyl  radical  replaces  an  amino-hydrogen  and  is 
therefore  joined  to  the  nitrogen,  R — NH — OH ;  these  reduce  Fehling's  solution  even  in  the 
cold  and  on  energetic  reduction  yield  primary  amines. 

Also  the  Alkylhydrazines,  RNH  •  NH2,  R2N  •  NH2,  etc.,  unlike  amines,  reduce  Fehling's 
solution  in  the  cold  and  give  characteristic  reactions  with  aldehydes  and  ketones. 

The  Diazo-compounds  of  the  methane  series  are  of  slight  importance,  whilst  those  of  the 
aromatic  series  are  a  very  important  class  of  compounds;  the  former  differ  from  the  la'.ter 
VOL.  II.  16 


242  ORGANIC    CHEMISTRY 

in  that  the  characteristic  divalent  nitrogen  group,  — N  =  N — ,  has  its  valencies  saturated 
by  only  one  carbon  atom.  They  may  be  obtained  by  diazotising,  by  means  of  nitrous  acid, 
aliphatic  amines  with  the  amino-group  united  to  a  carbon  atom,  the  other  valencies  of 
which  are  saturated  by  a  carbonyl  (CO)  or  cyanogen  group  and  by  at  least  one  hydrogen 
atom. 

Diazomethane,  CH2N2,  which  is  a  yellow,  odourless,  poisonous  gas,  is  prepared  from 
hydroxylamine  and  dichloromethylamine,  or  by  the  action  of  an  alkali  on  nitrosomethyl- 
urethane,  CH3-  N(NO)  •  CO  •  OC2H5.  Oxidation  of  aromatic  hydrazones  (see  p.  246;  also 
Monoses)  yields  diphenyldiazomethane  and  similar  compounds. 

V.  PHOSPHINES,   ARSINES,   AND   ALKYL  METALLIC  COMPOUNDS 

Like  ammonia,  the  hydrogen  derivatives  of  phosphorus,  arsenic,  antimony,  etc.,  give 
rise  to  alkyl  compounds  which  have  very  feebly  basic  characters  and  very  unpleasant 
odours. 

1.  PHOSPHINES.    These  are  gases  or  colourless  liquids  with  repulsive  odours.    Their 
basic  properties  and  their  stability  towards  water  become  more  marked  as  the  number  of 
alkyl  groups  increases.     They  are  readily  oxidisable  with  nitric  acid,  the  remaining  hydrogen 
atoms  of  the  PH3  being  transformed  into  hydroxyl  groups.     The  quaternary  phosphonium 
bases  are  very  strongly  basic,  and,  unlike  the  corresponding  ammonium  bases,  they  lose 
an  alkyl  group  in  the  form  of  a  saturated  hydrocarbon  when  heated,  the  residue  being  a 
trialkylphosphonium  oxide. 

CnH2rt+1PH2  (CnH2B+1)2PH  (CBH2n+1)3P  (CnH2n+1)4P-OH 

Primary  phosphine  Secondary  phosphine  Tertiary  phosphine  Tetralkylphosphonium 

hydroxide 

CnH2n+1PO(OH)2  (CnH2rt+1)2PO-OH  (CnH2n  +  1)3PO 

Alkylphosphonic  acid  Dialkylphosphonic  acid  Trialkylphosphine  oxide 

The  primary  and  secondary  phosphines  are  formed  by  heating  phosphonium  iodide 
with  alkyl  iodides  and  zinc  oxide,  whilst  the  tertiary  phosphines  and  phosphonium 
derivatives  are  obtained  from  hydrogen  phosphide,  PH3,  and  alkyl  halogen  compounds. 

2.  ARSINES.     Well-known  primary  and   secondary  compounds  are  :    methylarsenic 
dichloride,   CH3AsCl2    (liquid,  b.-pt.    135°);    dimethylarsenic   chloride,    (CH3)2AsCl  (b.-pt. 
100°);    dimethylarsine,    (CH3)2AsH   (b.-pt.   36°);   dimethylarsenic  acid   or  cacodylic  acid, 
(CH3)2AsO  •  OH,  etc.     The  tertiary  arsines  are  obtained  by  the  action  of  sodium  arsenide, 
AsNa3,  on  alkyl  iddides  : 

3C2H5I  +  AsNa3  =  3NaI  +  As(C2H5)3; 

they  are  liquids  slightly  soluble  in  water,  with  which  they  do  not  form  bases.  The 
quaternary  arsonium  compounds,  e.  g.,  (CH3)4AsI  (tetramethylarsonium  iodide ),  obtained 
from  the  tertiary  arsines  and  alkyl  iodides,  are,  however,  very  energetic  and  are  able  to 
give,  with  moist  silver  oxide,  tetramethylarsonium  hydroxide.  The  derivatives  of  cacodyl 

[(CH^s  -  As(CH3)2] 

were  studied  by  Bunsen  (1837-1843),  who  obtained  cacodyl  oxide, 

(CH3)2As-0-As(CH3)2, 

by  distilling  arsenic  trioxide  with  potassium  acetate  (this  reaction  serves  as  a  delicate  test 
for  acetates  in  mixtures) : 

As203  +  4CH3  •  COOK  =  2C02  +  2K2C03  +  [As(CH3)2]20. 

With  hydrochloric  acid,  cacodyl  oxide  gives  cacodyl  chloride,  (CHg^sCl. 

Many  of  these  cacodyl  compounds  are  liquids  which  ignite  in  the  air  and  have  nauseating 
odours ;  the  cacodyl  behaves  like  a  true  electro-positive  element. 

3.  Various  alkyl  derivatives  are  known  of  antimony  (stibines),  boron,  silicon,  bismuth, 
tin,  etc.,  but  these  are  of  little  pract'cal  importance. 

4.  ALKYLMETALLIC    (Organometallic)    DERIVATIVES.     These    are    ob- 
tained from  various  metallic  chlorides  or  from  the  metals  themselves   (Zn, 
Hg,  Mg,  Al,  etc.)  by  the  action  of  halogen  derivatives  of  the  hydrocarbons. 


GRIGNARD'S    REACTION  243 

They  are  generally  colourless  liquids  with  low  boiling-points,  and  some  of 
them  are  violently  decomposed  by  water  and  ignite  in  the  air.  Of  importance 
for  many  organic  syntheses  are  the  zinc-alkyls  (see  pp.  33,  125). 

ZINC  METHYL  :  Zn(CH3)2,  is  a  colourless,  highly  refractive  liquid,  sp.  gr. 
1'39,  b.-pt.  46°,  and  has  an  intense,  repulsive  odour;  it  ignites  in  the  air, 
forming  zinc  oxide,  and  with  water  gives  methane  and  zinc  hydroxide.  It  is 
formed  in  two  phases,  as  follows,  and  is  separated  by  distillation  : 

(a)  CH3I  -f-  Zn  =  Zn(CH3)I  (zinc  methyl  iodide,  solid); 

(b)  2Zn(CH3)I  =  Znl  -f  Zn(CH3)2. 

GRI GN ARD '  S  REACTION.  Mention  has  already  been  made  of  the  use  of  this  reaction 
in  synthesising  the  saturated  hydrocarbons  (p.  33).  One  molecule  of  a  monohalogenated 
(Br  or  I)  compound,  in  presence  of  absolute  ether,  combines  with  an  atom  of  magnesium  : 
Mg  -f-  C2H5Br  =  C2H5MgBr  (ethyl  magnesium  bromide),  and  with  compounds  containing 
several  carbon  atoms  there  is  always  formed,  as  a  secondary  product,  a  saturated  hydro- 
carbon. The  ether  probably  takes  part  in  the  reaction,  forming  an  intermediate  product, 
C2H5-Mg.Br[(C2H5)20]. 

The  latter,  and  also  the  alkyl  magnesium  halogen^  compounds,  when  dissolved  in  ether, 
are  highly  reactive  and  form  additive  compounds  with  aldehydes,  ketones,  and  even 
esters  of  mono-  and  poly-basic  carboxylic  acids;  with  water  these  additive  compounds 
then  give  the  corresponding  secondary  and  tertiary  alcohols,  the  reaction  occurring  in  the 
following  two  phases  (R  =  alkyl) : 

/O  •  Mgl 
R  •  CHO  +  R'Mgl  =  R  •  C^-R'  ->    -f  H20  =  I  •  Mg  •  OH  +  R  •  CH(OH)  R 

Aldehyde  Alkyl  mag-  \H  Secondary 

nesium  iodide  alcohol 

/OMg  •  Br 
H.COOC2H5+C2H5MgBr=C2H5-C^H  ->     +C2H6-MgBr  = 

Ethyl  formate  OCoHc 

/OMgBr 
Br  •  Mg  •  OC2H5  +  C2H5  •  C^-H  -*•       +  H20  =  BrMgOH  +  C,H6  •  CH(OH)  •  C2H5 

^C2H5  Diethylcarbinol 

If  esters  of  other  monobasic  acids  are  used  instead  of  a  formic  ester,  tertiary  alcohols 
are  obtained,  whilst  esters  of  dibasic  acids  give  dihydric  alcohols.  Hence,  by  means  of 
the  Grignard  reaction,  the  carboxylic  oxygen  of  any  acid  (starting  from  the  corresponding 
ester)  is  ultimately  replaced  by  two  alkyl  residues.  Similar  behaviour  is  shown  by  acid 
chlorides  and  anhydrides,  which  also  contain  carbonylic  oxygen  ( — CO — ). 

With  nitriles,  ketonimides  and  ketones  are  obtained  : 


, 

R-CN+R'MgI=R-C(  ->     +H20  = 

\R' 

IMgOH  +  R  •  C( :  NH)  •  R'    ->     +  H20  =  NH3  +  R-CO  •  R'  (ketone). 
Further,  with  dry  C02,  alkyl  magnesium  compounds  give  organic  acids  : 

R'Mgl  +  C02  =  R'  •  COOMg  •  I     ->     +  HX  =  IMgX  +  R' •  COOH  (acid). 

Other  most  varied  organic  syntheses  have  been  rendered  possible  of  late  years  by  the 
Grignard  reaction. 

VI.  ALDEHYDES   AND   KETONES  :  CnH2nO 

The  elimination  of  two  atoms  of  hydrogen  by  means  of  an  oxidising  agent 
(e.  g.,  potassium  dichromate  and  dilute  sulphuric  acid,  or  sometimes  even  the 
oxygen  of  the  air)  from  a  primary  or  secondary  alcohol  yields  an  aldehyde 
or  a  ketone  :  R  •  CH2  •  OH  +  O  =  H20  +  R  •  CHO  (aldehyde),  or 

R  •  CH(OH)R/  +  0  =  H20  +  R  •  CO  •  R'  (ketone). 


244  ORGANIC    CHEMISTRY 

The  aldehydes  have  a  strong  reducing  action,  as  they  fix  oxygen  and 
become  converted  into  acids  with  fhe  same  numbers  of  carbon  atoms,  whilst 
the  ketones  resist  oxidising  agents,  and,  if  these  are  very  energetic,  are 
oxidised  to  acids  containing  fewer  carbon  atoms  than  the  original  ketones. 

(a)  ALDEHYDES 

The  first  members  of  this  series  are  neutral  liquids  with  pronounced  and 
often  disagreeable  odours  (formaldehyde  is  a  gas)  and  are  soluble  in  water, 
whilst  the  higher  ones  gradually  become  solid  and  insoluble.  Their  boiling- 
points  are  much  lower  than  those  of  the  corresponding  alcohols. 

The  aldehydes  are  formed  when  a  calcium  or  barium  salt  (or  even  two  salts) 
of  a  monobasic  organic  acid  is  dry  distilled  with  calcium  or  barium  formate 
(reducing  agent)  :    (R  •  COO)2Ca  +  (H'COO)2Ca  =  2CaC03  +  2R  •  CHO. 
,    They  are  also  obtained  on  heating  with  water  compounds  containing  two 
halogen  atoms  united  to  the  same  carbon  atom  : 

CH3  •  CHC12  (ethylidene  chloride-)  +  H20  =  2HC1  +  CH3  •  CHO. 
The  constitution  of  the  aldehydes  may  be  deduced  from  their  methods  of 

7° 
formation  (e.  g.,  the  latter)  and  the  characteristic  aldehyde  group  is  —  C\ 

XH 

PROPERTIES.  They  are  substances  of  considerable  and  varied  reac- 
tivity. With  oxidising  agents  they  are  transformed  into  acids,  and  this 
reducing  property  is  readily  manifested  in  their  reduction  of  ammoniacal  silver 
nitrate  solution  (22  per  cent,  ammonia  solution  and  10  per  cent,  of  dilute  silver 
nitrate  diluted  with  its  own  volume  of  10  per  cent,  sodium  hydroxide  solution  ; 
or  1  gram  of  silver  nitrate  dissolved  in  30  c.c.  of  water  and  dilute  ammonia 
added  as  long  as  no  precipitate  forms)  or  of  Fehling's  solution  (the  latter, 
however,  is  not  reduced  by  aldehydes  containing  as  many  as  8  or  9  carbon 
atoms). 

In  their  turn,  the  aldehydes  are  reconverted  into  the  primary  alcohols 
when  reduced  with  nascent  hydrogen;  with  PC15,  they  give  ethylidene 
chlorides  again. 

Hydrocyanic  acid,  ammonia,  sodium  hydrogen  sulphite,  and  sometimes 
alcohol  and  acetic  anhydride  (also  the  alkyl  magnesium  halogen  compounds  : 
see  above,  Grignard's  Reaction)  form  characteristic  additive  products  with  the 
aldehydes  : 

CH3  •  CHO  +  2C2H5  •  OH  (+  a  little  HC1)  =  H20  +  CH3  •  CH(OC2H5)2  (acetal) 

which  is  an  ether  of  the  hypothetical  glycol  (dihydric  alcohol),  CH3  •  CH(OH)2  ; 
the  latter,  however,  does  not  exist  in  the  free  state,  since  two  hydroxyl  groups 
cannot  remain  joined  to  one  and  the  same  carbon  atom,  excepting  in  the  case  of 
chloral  hydrate  (see  later}  and  a  very  few  other  substances.1 

They  combine  with  sodium  and  ammonium  bisulphites  (very  concentrated 
solutions)  forming  crystalline  bisulphite  compounds  soluble  in  water  and  slightly 
so  in  alcohol  : 

,0  .OH 

C 
X 


C2H5  •  CC     +  S03HNa  =  C2H5  •  C^O  •  S02Na, 


H 

and  these  compounds,  when  heated  with  dilute  acid  or  with  alkali  (even 
Na2C03),  liberate  the  aldehyde  again.  This  reaction  hence  renders  possible 
the  separation  of  aldehydes  from  other  substances. 

1  See  Table  on  opposite  page. 


ALDOL    CONDENSATION 


245 


The  aldehydes  combine  with  ammonia,  forming  crystalline  aldehyde- 
ammonias  soluble  in  water  and  slightly  so  in  alcohol  but  insoluble  in  ether, 
for  example,  CH3  •  CH(OH)(NH2),  which  gives  the  aldehyde  again  when  heated 
with  a  dilute  acid.  But  formaldehyde,  with  ammonia,  readily  forms  poly- 
merised derivatives,  e.  g.,  hexamethylenetetramine,  (CH2)6N4  (see  later). 

With  hydrocyanic  acid  they  form  cyanohydrins  (p.  238). 

An  interesting  change  is  the  aldol  condensation,  that  is,  the  condensation 
of  2  mols.  of  an  aldehyde  brought  about  by  prolonged  heating  with  dilute 
mineral  acids,  dilute  alkalis,  or  even  aqueous  solutions  of  sodium  acetate 
Possibly  a  molecule  of  water  is  first  added  to  one  of  the  aldehydes  : 


CH3  •  C 


H 


H20  =  GH3  •  CH 


OH 
OH 


this  hypothetical  hydrate  then  condensing  with  another  molecule  of  aldehyde, 
with  separation  of  water  and  formation  of  a  hydro xyaldehyde  (aldol)  : 

/"\TT  /~V  /~\ 

CH3-CH/        +CH3-C/     =H20  +  CH3-CH(OH)-CH2-C^ 
\rm-  \H  \H 


(ft -Tiydroxybutyr aldehyde).  These  aldols  in  their  turn  readily  lose  a  molecule 
of  water,  forming  an  unsaturated  aldehyde,  which  may  also  be  obtained  directly 
(aldehyde  condensation)  by  heating  the  original  aldehyde  with  a  dehydrating 
agent  such  as  zinc  chloride  : 


CH3  •  C\^ 


H 


X 


H 


// 
CH3-CH:CH-Cf 


0 


H 


The  aldehydes,  especially  form-,  acet-,  and  prop-aldehydes,  etc.,  exhibit  a 
tendency  to  polymerise,  in  the  mere  presence  of  a  little  hydrochloric  or  sulphuric 
acid,  sulphur  dioxide,  zinc  chloride,  etc.  Acetaldehyde,  for  example,  gives 


DERIVATIVES   OF  ACETALS 


Name 

Formula 

Boiling-point 

Specific  gravity 

ALKYL  DERIVATIVES 

Methylal      . 

CH2(OCH3)2 

41-3°-41-7°(  749-8  mm.) 

0-862  (18°) 

Diethylmethylal   . 

CH2(OC2H5)2 

87° 

0-834  (20°) 

Dipropylmethylal 

CH2(OC3H7)2 

136° 

0-834  (20°) 

Diisopropylmethylal 
Diisobutylmethylal 

CH2(OC3H7)2 
CH2(OC4H9), 

118° 
164° 

0-831(20°) 
0-824  (20°) 

Diisoamylmethylal 

CH2(OC5HU)"2  +  H20 

206° 

0-835  (20°) 

Dihexylmethylal 

CH2(OC6H13)2 

174°-  175° 

0-822  (15°) 

Dioctylacetal 

CH3-CH(OC8H17)2 

289° 

0-848  (  15°) 

Dimethylacetal 

CH3-CH(OCH3), 

63° 

0-865(22°) 

Diethylacetal 

CH3-CH(OC2H5)"2 

102-9° 

0-831(20°) 

Dipropylacetal 

CH3-CH(OC3H.)2 

147° 

0-825  (22°) 

Diisobutylacetal 

CH3-CH(OC4Ho)., 

170° 

0-816  (22°) 

Diisoamy  la  cetal 

CH3-CH(OC5Hn)"2 

211° 

0-835  (  15°) 

ACID  DERIVATIVES 

Methylenediacetate 

CH2(0-  CO-  CH3)2 

170° 

. 

Ethylenodiacetate 

CH3-  CH(0-  CO-  CH3)2 

169° 

1-073  (  15°) 

Ethylenedipropionate 

CH3-CH(0-CO-02H5)2 

192° 

1-020(15°) 

Ethylenedi  tm  ty  ra  te 

CH3-CH(0-CO-  C,H7), 

215° 

0-985  (15°) 

Ethylenediisovalerate 

* 

CH3-  CH(0-CO-  C,,H9)"2 

225° 

0-947  (15°) 

246  ORGANIC    CHEMISTRY 

two  isomerides  :    paraldehyde,  m.-pt.  10°,  b.-pt.  124°,  and  metaldehyde,  which 
sublimes  at  100°  : 

/)-CH(CH3)x 
3C2H4O  =  CH3  •  CH<  0. 


These  no  longer  react  with  ammonia,  sodium  bisulphite,  silver  nitrate,  and 
hydroxylamine,  but  they  yield  the  aldehyde  again  when  distilled  in  presence 
of  a  small  quantity  of  dilute  sulphuric  acid. 

With  alkalis,  even  dilute  alkalis,  many  aldehydes,  especially  the  more  simple 
ones  of  the  fatty  series,  resinify,  whilst  some  give  rise  to  an  alcohol  and  an 
acid  : 

S° 
2HC\      (formaldehyde)  +  H2O  =  CH3  •  OH  +  H  •  C02H  (formic  acid). 

XH 

With  halogens  the  aldehydes  give  substitution  products,  and  with  hydrogen 
sulphide  various  complex  products  (ihioaldehydes,  etc.)  with  characteristic 
odours. 

With  hydroxylamine,  aldehydes  form  aldoximes,  which  are  resolved  into 
their  components  when  boiled  with  acids,  and  yield  nitriles  when  treated  with 
dehydrating  agents  :  CH3  •  CHO  +  NH2  •  OH  =  H20  +  CH3  •  CH  :  N  •  OH. 

A  similar  action  is  exhibited  by  the  hydrazines  (as  hydrochloride  or  acetate 
in  acetic  acid  solution  containing  sodium  acetate  ;  the  most  suitable  is  phenyl- 
hydrazine),  which  give  characteristic,  stable,  and  often  crystalline  compounds, 
termed  hydrazones  : 

CH3  •  CHO  +  C2H5  •  NH  •  NH2  (ethylhydrazine)  = 
H20  -f-  CH3  •  CH  :  N'NH  •  C2H5  (acetaldehyde  ethylhydrazone)  ; 

by  nascent  hydrogen  (4H)  this  is  converted  into  2  mols.  of  primary  amine  : 

2CH3  •  CH2  •  NH2. 

With  oxidising  agents  the  phenylhydrazone  gives  diphenyldiazomethane, 
(C6H5)2C:N2. 

Characteristic  of  the  aldehydes  is  also  the  formation  of  crystalline  semicar- 
bazones  by  the  action  of  the  hydrochloride  of  semicarbazide,  NH2  •  CO  •  NH  •  NH2 
(obtained  by  the  interaction  of  potassium  cyanate  and  hydrazine  hydrate)  : 

B  '  CHO  +  NH2  •  CO  •  NH  •  NH2  =  H20  +  B  •  CH  :  N  •  NH  •  CO  •  NH2. 

Both  the  hydrazones  and  semicarbazones  serve  for  the  separation  of  the 
aldehydes  from  other  substances  and  for  their  quantitative  determination. 

From  aqueous  liquids  aldehydes  are  separated  by  means  of  metanitrobenz- 
hydrazide,  with  which  they  form  insoluble  condensation  products. 

A  gaseous  mixture  containing  as  little  as  0*5  mgrm.  of  formaldehyde  per 
100  c.c.  precipitates  grey,  metallic  mercury  in  the  cold  when  passed  through 
Federer's  mercuric  solution. 

Finally  a  characteristic  qualitative  reaction  which  is  given  generally  by  the 
aldehydes  and  is  very  sensitive  is  that  of  Schiff.  It  consists  in  shaking  the 
liquid  to  be  tested  with  a  solution  (0'02  per  cent.)  of  fuchsine  previously 
decolorised  by  a  current  of  sulphur  dioxide.  Traces  of  an  aldehyde  produce  a 
reddish-violet  coloration  (it  is  uncertain  if  pure  ketones  also  give  this  reaction). 

Another  reaction  characteristic  of  the  aldehydes  and  not  given  by  ketones 
is  that  with  benzosulphinehydroxamic  acid  or  with  nitrohydroxylaminic  acid, 


OH  •  NO  :  N  '  OH,  which  forms  hydroxamic  acids,  R  •  Csf  ,  the  latter 

X 
producing  a  cherry-red  coloration  with  ferric  chloride. 


FORMALDEHYDE 


247 


FORMALDEHYDE  (or  Methanal),  H'CHO,  was  discovered  by  A.  W. 
Hofmann  in  1868  by  passing  air  saturated  with  methyl  alcohol  vapour  over  a 
red-hot  platinum  spiral.  Kekule  obtained  it  pure  in  1892. 

If  it  occurs  out  of  contact  with  air,  the  oxidation  of  methyl  alcohol  in 
presence  of  the  catalyst  is  endothermic  :  CH3  •  OH  =  CH2O  +  H2  —  28  Cals. ; 
as  a  secondary  reaction  part  of  the  aldehyde  may  decompose  with  formation 
of  CO  and  H2  and  development  of  3'6  Cals.  On  the  large  scale  it  is  hence  neces- 
sary to  prolong  the  heating  so  as  to  maintain  the  most  suitable  temperature 
for  the  copper  catalyst  (500°  to  600°),  which  rapidly  loses  its  activity  under 
such  conditions.  In  presence  of  oxygen  (theoretically  200  litres  of  air  measured 
at  15°  per  100  grams  of  methyl  alcohol),  however,  the  reaction  is  exothermic, 
but  the  reaction,  CHg  •  OH  +  O  =  CH20  +  H2O  +  30'2  Cals.,  which  should 
be  the  primary  reaction,  is  not  verified.  It  seems  rather  that  the  copper 
catalyst  gives  an  oxide,  which  with  the  carbon  monoxide  and  hydrogen  formed 
(according  to  the  first  equation)  would  regenerate  the  copper  with  formation 
of  H2O  and  CO2  and  generation  of  sufficient  heat  to  cause  the  reaction,  once 
started,  to  proceed  without  further  heating. 

Formaldehyde  is  a  gas  which  irritates  the  eyes  and  liquefies  at  —  21°  to  a 
mobile,  colourless  liquid  having  the  sp.  gr.  0'8153~(or  0'9172  at  —  80°)  and 
solidifying  at  —  92°.  It  is  very  soluble  in  alcohol  or  water  (52'5  per  cent.), 
and  is  placed  on  the  market  in  the  form  of  40  per  cent,  (by  vol.  or  36  per  cent, 
by  weight)  aqueous  solution  1  under  the  name  of  formalin  or  farmol;  this  aqueous 
solution  gradually  undergoes  change  (it  lasts  at  most  six  months),  so  that 
the  commercial  product  often  contains  12  to  15  per  cent,  of  methyl  alcohol, 
this  being  added  to  prevent  separation  of  polymerised  compounds  (see  later). 
The  heat  of  formation  of  the  gaseous  aldehyde  is  25  Cals.,  the  heat  of  solution 
in  water  being  15  Cals. 

1  The  concentrations  of  commercial  aqueous  solutions  of  formaldehyde  may  be  deduced 
from  the  specific  gravities  by  means  of  the  following  table  (Auerbach,  1905) : 


18° 


p.gr.at'J 

1-0064 
1-0090 
1-0126 
1-0172 
1-0218 
1-0311 
1-0410 
1-0568 
1-0719 
1-0853 
1-1057 
1-1158 


Grams  of  CH29  in  100  c.c. 
of  solution 

2-24 

3-50 

4- 60 

6-51 

8-37 
11-08 
14-15 
19-89 
25-44 
30-17 
37-72 
41-87 


Grams  of  OH2O  in  100  grams 
of  solution 

2-23 
•*  3-45 

4-60 

6-30 

8-0 
10-74 
13-59 
18-82 
23-73 
27-80 
34-11 
37-53 


If  the  aldehyde  is  pure  and  leaves  no  residue,  the  percentage  by  volume,  if  greater  than  23, 
should  be  increased  by  about  5. 

The  analysis  of  commercial  formalin  is  based  on  the  following  reaction  of  Blank  and  Finken- 
beiner  :  2CH20  +  2NaOH  +  H202  =  H2  +  2H20  +  2H  •  C02Na.  Three  grams  of  the  formal- 
dehyde solution  is  poured  into  a  long-necked  flask  containing  25  c.c.  of  2N-caustic  soda  solution 
(free  from  carbonates),  the  liauid  being  mixed  and  50  c.c.  of  hydrogen  peroxide  solution  (neutral- 
ised or  of  known  acidity )  carefully  added,  3  minutes  being  taken  to  make  this  addition.  After 
seven  to  eight  minutes,  the  excess  of  alkali  remaining  is  titrated  with  2N-sulphuric  acid.  With 
every  cubic  centimetre  of  the  2N-alkali  that  has  reacted  corresponds  0-06  gram  of  formaldehyde. 
Litmus  purified  several  times  with  alcohol  should  be  used  as  indicator. 

The  estimation  of  the  aldehyde  may  also  be  carried  out  with  ammonia  (see  succeeding  Note ). 

Brautigam  (1910)  suggested  the  determination  of  formaldehyde  by  adding  to  it  excess  of  clear 
calcium  hypochlorite  solution.  After  a  time  the  solution  deposits  calcium  carbonate,  which  is 
filtered,  washed,  and  weighed ;  1  mol.  of  CaC03  corresponds  with  1  mol.  of  formaldehyde. 

To  determine  the  methyl  alcohol  which  may  be  present,  5  c.c.  of  the  solution,  diluted  with 
100  c.c.  of  water,  is  distilled  with  an  excess  of  ammonia  (about  10  c.c.  of  concentrated  ammonia), 
50  c.c.  of  the  distillate  being  collected  in  a  100  c.c.  flask  and  made  up  to  volume  with  water. 
The  methyl  alcohol  in  5  c.c.  of  this  solution,  which  contains  only  negligible  traces  of  formaldehyde, 
is  determined  by  the  iodine  method  (see  p.  129). 


248 

A  question  which  has  been  under  discussion  for  many  years  is  the  possible  formation 
of  formaldehyde  as  the  first  product  in  the  natural  synthesis  of  carbohydrates  (see  Sugar) 
in  the  leaves  of  plants,  from  carbon  dioxide  under  the  influence  of  chlorophyll. 

Numerous  sensitive  reagents  have  been  employed  to  detect  microscopically  the  tran- 
sitory formation  of  formaldehyde  in  living  leaves,  but  almost  all  these  reagents  are  poisonous 
to  plants  and  no  decisive  results  have  been  obtained,  even  those  of  Pollacci  (1907),  who 
distilled  the  leaves  with  water  and  tested  for  formaldehyde  in  the  distillate,  being  doubtful. 
Schryver  (1910)  has  succeeded  in  establishing  the  formation  of  aldehyde  in  green  plants  in 
sunlight,  by  making  use  of  a  very  sensitive  reagent  (detecting  1  part  of  aldehyde  per  million) 
consisting  of  a  solution  of  phenylhydrazine,  potassium  ferricyanide,  and  hydrochloric 
acid;  this  reagent  gives  a  red  coloration  with  formaldehyde  or  with  the  methylene 
derivative  which  chlorophyll  would  form  with  the  aldehyde. 

Angelico  and  Catalano  (1913)  have  demonstrated  the  presence  of  formaldehyde  in  the 
juices  of  green  plants  by  means  of  a  very  sensitive  reagent,  atractylin,  which  is  the  active 
component  of  the  glucoside  of  Atractylis  gummifera.  Treatment  of  a  trace  of  atractylin 
with  two  or  three  drops  of  concentrated  sulphuric  acid  yields  a  yellow  coloration,  which 
changes  to  violet  and  then  to  blue  on  addition  of  a  drop  of  a  very  dilute  solution  of 
formaldehyde;  this  reaction  appears  to  be  specific  for  formaldehyde. 

PROPERTIES.  Formaldehyde  polymerises  to  a  white  buttery  mass  of  paraformalde- 
Tiyde,  6CH20  +  H2O,  which  is  also  formed  in  soft  flocks  when  the  aqueous  aldehyde  is 
evaporated.  Paraformaldehyde  dissolves  in  hot  water  and  then  shows  all  the  properties 
of  a  solution  of  formaldehyde.  Treatment  of  formaldehyde  solution  with  concentrated 
sulphuric  acid  results  in  the  separation  of  a  white  crystalline  mass  of  polyoxymethylene 
(improperly  termed  trioxymethylene),  of  which  four  modifications  (a—,  ft—  y—  and  8— 
oxymethylenes)  are  known;  these  are  insoluble  in  alcohol  or  ether,  have  m.-pts.  165°  to 
172°,  and  behave  like  formaldehyde  when  heated  or  in  aqueous  solution.  True  a-trioxy- 
methylene,  produced  under  definite  conditions  (e.  g.,  with  a  trace  of  sulphuric  acid)  from 
formaldehyde  vapour  in  the  hot,  forms  white,  pliable,  acicular,  highly  refractive  crystals, 
m.-pt.  63°,  which  sublime  readily  and  are  soluble  in  water,  alcohol,  or  ether;  its  true 
constitution  is  CH2  •  0  •  CH2. 

O  •  CH2  •  O 

These  different  solid  polymerides  of  formaldehyde  yield  vapour  of  the  latter  when 
heated,  and  hence  serve  as  convenient  and  portable  disinfectants  (as  pastilles),  being  sold 
under  various  trade  names  (triformol,  paraformol,  etc.). 

With  ammonia  formaldehyde  gives,  not  an  aldehyde-ammonia,  but  hexamethylene- 
tetramine  (urotropine),1  C6H12N4,  which  is  crystalline  and  of  feebly  monobasic  character; 
this  compound  is  used  as  an  antifermentative  to  preserve  milk  and  to  fix  the  excess  of 
sulphurous  acid  in  wine  (see  note,  p.  1 87 ),  and  medicinally  as  a  solvent  for  uric  acid  in  the 
treatment  of  uric  arthritis.  With  hot,  dilute  caustic  sodsu  solution  the  aldehyde  does  not 
resinify,  but  gives  methyl  alcohol  and  formic  acid  (see  above);  with  the  concentrated  alkali 
it  yields  only  formic  acid  and  nascent  hydrogen,  and  in  these  conditions  exerts  a  strong 
reducing  action  and  separates  Ag,  Au  and  Hg  from  their  salts. 

Formaldehyde  is  one  of  the  most  active  substances  chemically  and  lends  itself  to  many 
varied  organic  syntheses.  Under  the  action  of  minimal  proportions  of  certain  alkalies, 
e.  g.,  lime  water,  it  undergoes  condensation  to  glycollic  aldehyde,  OH  •  CH2  •  CHO,  and 
then  to  formose,  C6H1206,  the  principal  component  of  which  is  a-acrose  or  inactive  fructose. 

1  This  reaction  was  proposed  by  L.  Legler  in  1883  as  a  means  of  estimating  formaldehyde 
in  commercial  solutions:  6CH20  +  4NH3  =  (CH2 )6N4  +  6H20 ;  the  reaction  is,  however, 
slow  and  the  method  not  very  accurate.  F.  Hermann  (191 1 )  has  rendered  it  more  rapid  and  exact 
in  the  following  manner.  Four  cubic  centimetres  of  the  formalin  is  weighed  into  a  150  c.c. 
flask  with  a  ground  stopper,  and  about  3  grams  of  pure  powdered  ammonium  chloride  and  exactly 
25  c.c.  of  2N-caustic  soda  (equivalent  to  50  c.c.  of  normal  soda)  added.  The  flask  is  stoppered, 
and  shaken,  and,  when  the  mass  is  cool,  50  c.c.  of  water  and  4  drops  of  1  per  cent,  methyl  orange 
are  added  and  the  excess  of  alkali  titrated  with  normal  sulphuric  acid.  Deduction  of  the  volume 
of  acid  required  from  50  c.c.  gives  the  volume  of  soda  used  in  liberating,  from  the  ammonium 
chloride,  a  corresponding  amount  of  nascent  ammonia,  which  instantly  transforms  the  aldehyde 
into  hexamethylenetetramine.  The  latter  is,  however,  monobasic  and  reacts  with  part  of  the 
sulphuric  acid,  and,  in  order  to  obtain  the  number  of  grams  of  formaldehyde  in  the  quantity  of 
formalin  taken,  the  number  of  cubic  centimetres  of  soda  arrived  at  above  must  be  multiplied 
by  the  factor  0-06.  If  the  formalin  be  acid  initially,  the  acidity  must  be  determined  separately 
by  titration  with  soda  in  presence  of  phenolphthalein  and  the  50  c.c.  of  soda  increased  accordingly. 


MANUFACTURE    OF    FORMALDEHYDE     249 

With  bisulphite  solution  and  zinc  dust  it  yields  hydrosulphite  compounds  (see  Vol.  I., 
p.  586).  A  characteristic  and  very  sensitive  reaction  of  formaldehyde  is  that  proposed  by 
Rimini,  according  to  whom  a  mixture  of  phenylhydrazine  hydrochloride,  sodium  nitro- 
prusside,  and  caustic  soda  is  coloured  blue  even  by  minimal  traces  of  the  aldehyde. 

Formaldehyde  gives  Schiffs  reaction  (see  above)  even  in  presence  of  a  certain  amount 
of  sulphuric  acid,  whilst  acetaldehyde  does  not. 

MANUFACTURE.  In  1886  O.  Loew  replaced  the  platinum  used  as  catalyst  by  copper, 
the  yield  of  aldehyde  thus  obtained  being  31  per  cent,  of  the  theoretical  yield. 

In  1908  Orloff  devised  a  large-scale  plant  in  which  rectifying  columns  were  used, 
igniters  composed  of  heaps  of  platinised  asbestos  taking  the  place  of  the  initial  heating. 
Platinum  being  excluded  on  account  of  its  high  price  and  iron  owing  to  its  low  yield,  either 
silver  gauze  or  asbestos  impregnated  with  silver  was  used  as  catalyst,  the  yield  being 
almost  theoretical  (Ger.  Pat.  228,697;  U.S.  Pats.  1,067,668  and  1,100,076).  The  most 
suitable  temperature  for  the  formation  of  the  aldehyde  is  about  450°,  decomposition  into 
CO  and  H2  occurring  if  this  is  surpassed.  The  catalytic  layer  should  not  exceed  a  certain 
thickness.  The  methyl  alcohol  is  used  at  a  concentration  of  90  per  cent.,  but  98  per  cent. 
is  better,  provided  that  not  more  than  1  per  cent,  of  acetone  is  present.  In  order  to  obtain 
the  proper  proportion  between  alcohol  and  air  (1  part  of  alcohol  and  0-36  part  of  oxygen), 
the  latter  is  passed  through  alcohol  heated  to  about  52° ;  about  35  per  cent,  of  the  alcohol 


FIG.  181. 

should  distil  unchanged,  whilst  65  to  70  per  cent,  is  transformed  into  aldehydes.  An 
apparatus  designed  by  Orloff  and  modified  by  F.  H.  Meyer  is  shown  in  Fig.  181.  The 
vessel  2  contains  a  supply  of  air  furnished  by  the  compressor  1,  this  passing  gradually 
into  the  saturator  4,  where  it  meets  a  spray  of  alcohol  from  the  tank  3.  By  means  of  steam 
coils  the  saturator  is  kept  at  52°,  the  air,  saturated  with  alcohol  vapour,  at  this  temperature 
proceeding  to  the  catalysing  chamber  5,  in  which  the  alcohol  is  partially  oxidised  to 
aldehyde.  The  mixture  of  aldehyde,  alcohol,  nitrogen  and  water  vapour  from  5  enters 
at  the  bottom  of  the  rectifying  column  6,  in  which  the  temperature  is  regulated  so  that  a 
40  per  cent,  aqueous  formaldehyde  solution  condenses ;  this  is  discharged  into  the  separator 
8,  and  thence  into  the  vessel  B.  The  excess  of  alcohol  vapour  passes  from  the  top  of  the 
column  to  the  condenser  7,  the  condensed  alcohol  being  collected  in  the  tank  12  and  thence 
pumped  to  the  tank  3,  into  which  a  further  amount  of  alcohol  is  forced  by  the  pump  14- 
The  nitrogen  and  other  gases  escaping  from  11  are  washed  with  a  little  water  in  the  tower 
9  before  being  dispersed  into  the  air ;  the  small  amount  of  dilute  methyl  alcohol  thus 
recovered  is  rectified  in  the  column  10,  from  which  the  condensed  water  is  discharged  at 
A,  while  the  alcohol  vapour  from  the  top  of  the  column  is  condensed  in  11,  the  liquid 
flowing  into  the  tank  12. 

The  catalyser  is  formed  of  a  bundle  of  six  copper  tubes  60  cm.  long  and  5  cm.  in  diameter, 
fixed  to  tubulated  plates  so  as  to  form,  in  the  cylinder  containing  these  tubes,  a  distribut- 
ing chamber  at  the  entrance,  and  a  collecting  chamber  for  the  oxidised  gases  at  the  exit, 
of  the  tubes.  At  the  front  end  of  each  tube  is  a  compact  roll  of  fine  copper  gauze,  forming 
a  sort  of  plug  11  cm.  long,  this  being  preceded  by  a  small  tuft  of  platinised  asbestos  which 


250  ORGANIC    CHEMISTRY 

automatically  ignites  the  alcohol  vapour.  The  formaldehyde  condensing  in  the  column  6 
(if  the  height  and  temperature  of  this  are  properly  regulated)  contains  14  per  cent,  of  methyl 
alcohol,  52  per  cent,  of  water  and  40  per  cent,  of  formaldehyde.  Various  modifications 
in  the  saturator  have  been  suggested  (see  Ger.  Pat.  106,495,  1898).  Ignition  of  the  alcohol 
vapour  by  means  of  electrical  resistances  in  the  catalysing  apparatus  has  also  been 
attempted  (W.  Lob,  1912). 

Various  endeavours  which  have  been  made  to  prepare  formaldehyde  from  methane 
(e.  g.,  by  mixing  it  with  an  equal  volume  of  air  and  using  granulated  copper  at  600°  as 
catalyst)  have  not  yet  given  satisfactory  results  (Ger.  Pats.  109,014,  214,155,  286,731,  etc.), 
the  yields  being  very  low.  Further,  practical  success  has  not  attended  the  preparation  of 
formaldehyde,  either  by  reducing  formic  acid  vapour  mixed  with  hydrogen  in  presence  of 
various  metals  at  high  temperatures  (Ger.  Pat.  185,932,  1905),  or  by  heating  tin  formate 
at  180°  so  as  to  decompose  it  into  C02  and  formaldehyde  (Ger.  Pat.  183,856). 

USES.  Formaldehyde  has  considerable  antiseptic  power,  even  in  aqueous 
solution ;  its  use  in  foodstuffs  is  prohibited.  It  is  largely  used  at  the  present 
time  in  1  to  3  per  cent,  solutions  as  a  disinfectant  in  houses  and  for  the  preserva- 
tion of  readily  putrescible  substances  (1  part  in  2000  kills  bacteria  and  1  in 
1000  also  spores).  Its  vapour  has  an  acute  and  penetrating  odour  and  irritates 
the  eyes.  On  account  of  the  property  possessed  by  formaldehyde  of  combining 
with  proteins  to  form  insoluble  and  stable  products,  it  is  used  in  the  manufac- 
ture from  casein  of  articles  of  a  horny  consistency  (galalitTi)  and  in  making 
imitation  pegamoid;  also  in  preparing  photographic  films  with  gelatine,  for 
rendering  insoluble  or  hardening  coloured  gelatine  for  textile  printing,  and 
for  hastening  the  tanning  of  skins.  It  causes  the  polymerisation  and  resinifica- 
tion  of  phenols  (see  Formolite  reaction  of  petroleum,  pp.  71  and  91)  and  is 
consequently  used  in  large  quantities  in  making  baekelite  (see  Part  III :  chapter 
on  Phenol)  and  neradol,  which  replaces  tannin  in  the  tanning  of  hides.  The 
hydrosulphite  derivatives  (see  above)  are  largely  employed  in  the  dyeing  and 
printing  of  textiles. 

Owing  to  its  great  reactivity,  it  is  largely  used  in  organic  syntheses,  e.  g,, 
in  the  manufacture  of  aniline  dyes. 

Solid  and  liquid  disinfectants  containing  free  aldehyde  are  prepared  in 
large  number.  Thus,  lysoform  consists  of  a  soap  solution  of  formaldehyde, 
and  mixtures  or  compounds  of  the  aldehyde  with  sugar,  oil,  quinones,  amines, 
creosote,  ichthyol  (see  p.  103),  ricinoleic  acid  (ozoform),  etc.,  are  also  sold. 

STATISTICS  AND  PRICES.  The  price  of  commercial  40  per  cent,  formaldehyde  is 
about  £40  per  ton,  while  pure,  powdered  paraldehyde  costs  4s.  to  5s.  per  kilo. 

Germany  consumed  about  500  tons  of  formaldehyde  per  annum  before  the  war. 

Italy  produces  it  in  varying  amounts,  as  much  as  60  tons  per  annum  being  sometimes 
made  prior  to  the  war,  when  the  importation  was  about  250  tons  per  year. 

For  France  the  movements  of  the  aldehyde  are  as  follows  (tons) : 

1910  1914  1915  1916 

Importation    .         .     469  391  1047  613 

Exportation  25  16  83  33 

ACET ALDEHYDE  (Ethanal),  CH3  •  CHO,  is  a  colourless,  mobile  liquid,  sp.  gr.  0-801 
(at  0°),  b.-pt.  21°,  and  solidifies  at  —121°.  It  has  an  agreeable  but  suffocating  odour, 
and  it  polymerises  with  moderate  ease,  giving  the  paraldehyde  and  metaldehyde  (see  above). 
It  dissolves  in  water,  alcohol,  or  ether,  and  is  readily  converted  into  acetic  acid  by  oxidising 
agents. 

It  is  prepared  by  pouring  a  mixture  of  3  parts  of  90  per  cent,  alcohol  and  4  parts  of 
concentrated  sulphuric  acid  slowly  into  a  solution  of  3  parts  of  potassium  dichromate  in 
12  of  water,  the  liquid  being  kept  cool  meanwhile.  The  solution  is  then  heated  in  a  reflux 
apparatus  on  a  water-bath  and  subsequently  distilled.  The  mixture  of  alcohol,  aldehyde, 
and  acetal  thus  obtained  is  heated  to  50°  and  the  aldehyde  vapour  passed  into  cold  ether. 
On  passing  ammonia  into  this  solution,  crystallised  aldehyde-ammonia,  CH3  •  CH(OH)  •  NH2, 


CHLORAL  251 

separates;  this,*wlien  pressed  and  distilled  with  dilute  sulphuric  acid,  gives  pure  acetalde- 
hyde.  The  commercial  aldehyde  is  obtained  from  the  foreshots  of  alcohol  distillation,  from 
which  it  is  separated  by  simple  fractional  distillation. 

It  is  of  importance  in  many  organic  syntheses  and  in  the  production  of  silver  mirrors. 
The  price  of  50  per  cent,  solutions  before  the  war  was  2s.  per  kilo,  that  of  the  95  to  99 
per  cent,  product  3*.  Qd.,  and  that  of  the  purest  aldehyde  15-s.1 

METHYLAL,  H  •  CH(OCH3)2,  ACETAL,  CH3  •  CH(OC2H5)2  (see  p.  245). 

PROP  ALDEHYDE,  C2H5  .  CHO,  is  found  among  the  tarry  products  from  the 
distillation  of  wood.  Valeraldehyde,  C4H9  •  CHO,  boils  at  92°  and  begins  to  show 
a  diminution  in  solubility  in  water.  Normal  heptaldehyde  (cenantaldehyde),  C6H13  •  CHO, 
is  found  among  the  products  of  decomposition  of  castor-oil  when  this  is  subjected  to 
distillation  in  a  vacuum.  Nonyl  aldehyde,  C8H17  •  CHO,  occurs  in  the  oxidation 
products  of  oleic  acid  or,  better,  in  the  decomposition  products  of  the  ozonide  of  oleic  acid 
(Harries,  Molinari,  etc.);  it  boils  at  about  192°. 

CHLORAL  (Trichloroethanal),  CC13'CHO,  is  the  most  important  halo- 
genated  derivative  of  the  aldehydes.  It  is  a  dense  liquid  with  a  peculiar, 
penetrating  odour  and  boils  at  94 '4°.  It  is  prepared  by  passing  chlorine  into 
pure  alcohol  (96  per  cent.)  for  some  days,  the  hydrochloric  acid  formed  being 
collected.  At  first  the  mass  is  cooled,  but  is  afterwards  heated  to  60°  and  then 
to  100°,  the  stream  of  chlorine  being  suspended  when  a  little  of  the  liquid 
dissolves  completely  in  water.  The  reaction  may  be  accelerated  by  addition 
of  a  trace  of  iodine  or  ferric  chloride.  The  final  product  is  heated  to  boiling 
under  a  reflux  condenser  with  an  equal  amount  of  concentrated  sulphuric 
acid  in  a  lead-lined  apparatus.  After  evolution  of  hydrogeji  chloride  has 
ceased,  the  liquid  is  distilled  until  the  temperature  of  the  vapour  reaches 
100°,  the  distillate  being  subsequently  rectified  and  the  fraction  boiling  at  94° 
to  97°  collected  separately.  If  this  chloral  is  mixed  with  an  equimolecular 
proportion  of  water  it  forms  a  crystalline  mass  of  chloral  hydrate  (see  below), 
which  may  be  pressed  and  crystallised  from  chloroform,  CS2  or  benzene.  Chloral 
is  also  prepared  electrolytically  :  the  bath  contains  potassium  chloride  solution 
at  100°  and  is  fitted  with  a  diaphragm;  alcohol  is  passed  into  the  anode 
chamber,  where  chlorine  is  formed,  and  the  hydrogen  chloride  produced  at  the 
anode  (carbon)  is  neutralised  by  the  potassium  hydroxide  formed  (1  h.p.-hour 
yields  50  grams  of  chloral) ;  the  cathode  is  of  copper. 

Chloral  gives  the  reactions  of  the  aldehydes  and  is  used  in  medicine  as  an 
anaesthetic  and  soporific,  being  first  treated  with  water  to  form  the  crystalline 

OTT 
CHLORAL    HYDRATE,    CC13'CH<^,   which  is  readily  soluble  in  water 

(m.-pt.  57°) ;  this  is  one  of  the  few  compounds  having  two  hydroxyl  groups 
united  to  the  same  carbon  atom.  The  crystalline  alcoholates  or  Acetals, 
CC13  '  CH(OH)  •  OC2H5  and  CC13  •  CH(OC2H5)2,  corresponding  with  this  hydrate, 
are  known. 

Chloral  costs  about  6s.  per  kilo. 

ALDEHYDES   WITH   UNSATURATED    RADICALS 

ACRALDEHYDE  (Propenal,  Acrolei'n,  or  Allyl  Aldehyde),  CH2  :  CH  •  CHO,  is  formed 
when  fats  are  burned,  owing  to  loss  of  water  by  the  glycerol  present ;  a  similar  change 
takes  place  when  glycerol  is  heated  with  potassium  hydrogen  sulphate  or  boric  acid.  By 
distillation  of  200  c.c.  of  concentrated  glycerine  with  10  grams  of  potassium  bisulphate 

1  The  estimation  of  acetaldehydc  is  based  on  the  following  reaction  (Seyewetz  and  Bardin) : 

2Na2S03  +  2CH3  •  CHO  +  H2S04  =  Na2S04  +  (CH2  •  CHO,  NaHS03)2. 

The  aldehyde  is  diluted  to  7  to  8  per  cent,  and  about  10  c.c.  of  this  solution  is  poured  into  40  c.c. 
of  10  per  cent,  pure  sodium  sulphite  solution.  After  the  addition  of  a  few  drops  of  neutralised 
alcoholic  phenolphthalein  solution  the  liquid  is  cooled  to  4°  to  5°  and  titrated  with  normal  sul- 
phuric acid  until  it  is  decolorised.  This  occurs  when  no  further  combination  of  aldehyde  and 
sulphurous  acid  takes  place.  This  determination  is  not  affected  by  the  presence  of  alcohol, 
acetal,  or  paraldehyde. 


252  ORGANIC    CHEMISTRY 

X 

at  105°  to  110°  and  rectification  of  the  first  distillate  (140  to  150  c.c.),  3#  c.c.  of  acrolein 
are  obtained. 

Acrolein,  which  may  also  be  obtained  by  the  oxidation  of  allyl  alcohol,  is  a  liquid, 
b.-pt.  524°,  and  has  a  characteristic  pungent  odour.  When  oxidised,  it  yields  acrylic 
acid  and,  when  reduced,  allyl  alcohol.  It  has  all  the  chemical  properties  of  the  aldehydes 
and  polymerises  in  the  course  of  a  few  hours.  With  ammonia,  it  gives  a  solid,  basic 
condensation  product,  soluble  in  water  :  2C3H4O  +  NH3  =  H20  +  C6H9ON  (acrolein- 
ammonia,  which  gives  picoline  on  distillation).  Owing  to  its  double  linking,  acrolein 
unites  with  2  mols.  of  sodium  bisulphite,  and  the  resulting  product,  when  boiled  with  acid, 
gives  up  only  one  bisulphite  molecule,  namely,  that  combined  with  the  aldehyde  group. 

CROTONALDEHYDE,  CH3  •  CH  :  CH  •  CHO,  is  obtained  by  distilling  the  corre- 
sponding aldol,  CH3  •  CH(OH)  •  CH2  •  CHO,  at  140°  or  by  the  dehydrating  action  of  zinc 
chloride  or  sodium  acetate  on  the  saturated  aldehyde.  It  is  a  liquid  boiling  at  104°  and 
possessing  a  penetrating  odour,  and  its  constitution  is  shown  by  the  fact  that  it  yields 
crotonic  acid  when  oxidised  with  silver  oxide. 

CITRAL  (or  Geranial),  (CH3)2C  :  CH  •  CH2  •  CH2  •  C(CH3)  :  CH  •  CHO,  is  a  liquid  of 
pleasant  odour,  b.-pt.  229°,  and  occurs  in  many  essences  (of  mandarin,  citron,  lemon,  orange, 
and  most  abundantly — 60  per  cent. — in  that  of  Verbena  indiana  or  lemon-grass,  from 
which  it  is  separated  by  means  of  its  bisulphite  compound).  It  may  also  be  obtained  by 
the  gentle  oxidation  of  the  corresponding  alcohol,  geraniol,  which  boils  at  230°.  It  exists 
in  two  stereoisomeric  forms,  the  cis-  and  trans-modifications.  When  oxidised  with  potas- 
sium bisulphate  at  170°,  citral  is  transformed  into  cymene  (with  a  closed  ring)  with 
separation  of  water. 

CITRONELLAL,  (CH3)2C  :  CH  •  CH2  CH2  •  CH(CH3) .  CH2  •  CHO,  is  found  with 
citral  in  citron  oil  and  boils  at  208°. 

PROPARGYL  ALDEHYDE,  CH  |  C  •  CHO,  is  a  solid,  m.-pt.  60°,  and  is  obtained 
from  dibromoacrolein  by  way  of  the  acetal.  As  it  contains  the  group  CH  :  C,  it  forms 
metallic  derivatives  (see  pp.  110  and  112). 

(b)  KETONES   (R— CO— R') 

-These  have  the  carbonyl  group  attached  to  two  alcohol  radicals  and,  if 
the  latter  are  similar,  are  known  as  simple  ketones  and,  if  different,  mixed 
ketones.  The  first  member  must  contain  at  least  three  carbon  atoms.  They 
present  the  same  cases  of  isomerism  as  the  secondary  alcohols,  and  are  metameric 
with  the  aldehydes. 

Up  to  the  Cn-compound  they  are  liquid  and  beyond  that  solid,  but  all 
are  less  dense  than  water.  They  resist  feeble  oxidation,  but  energetic  oxidising 
agents  (dichromate  and  dilute  sulphuric  acid)  break  the  chain  of  the  ketone 
at  the  carbonyl  group,  thus  forming  an  acid  with  a  lower  number  of  carbon 
atoms  :  CH3  •  CO  •  CH3  +  40  =  H20  +  CO2  -f  CH3  •  C02H.  In  mixed  ketones, 
however,  the  carboxyl  is  united  mainly  to  the  smaller  alkyl  radical  (R  or  R'), 
but  the  acid  with  the  higher  alkyl  is  always  formed  to  some  extent.  With 
ammonia,  the  action  is  different  from  that  in  the  case  of  aldehydes  :  water  is 
eliminated  from  2  or  3  mols.  of  ketone  and  di-  and  tri-ketonamines  (or  acetona- 
mines),  e.  g.,  C6H13ON,  formed.  Further,  the  ketones  do  not  polymerise,  but 
they  form  condensation  products.  They  do  not  react  with  ammoniacal  silver 
solutions  or  with  Fehling's  solution,  and  are  hence  not  reducing  in  character 
(difference  from  aldehydes). 

With  phosphorus  pentachloride  they  give  the  corresponding  dichloro- 
derivatives;  for  instance,  acetone  gives  2-dichloropropane,  CH3  *  CC12  '  CH3. 

On  reduction,  they  yield  secondary  alcohols,  and  with  very  energetic  oxidis- 
ing reagents  (H202,  etc.)  they  form  characteristic  polymerised  ketonic  per- 
oxides, e.  g.,  [(CH3)2C02]2,  [(CH3)2CO2]3.  With  ethyl  orthoformate  they  give 
acetals,  (CH3)2C(OC2H5)2,  and  similarly  with  mercaptans  they  form  Mercaptols, 
e.  g.,  (CH3)2C(SC2H5)2,  which,  when  oxidised  with  permanganate,  gives 
Sulphonal,  (CH3)2C(SO2C2H5)2  (see  pp.  119  and  233). 


K  E_T  O  N  E  S  253 

Ketones,  which  generally  contain  the  group  CH3'OO,  form,  with  sodium 
bisulphite,  compounds  which  are  crystalline  and  hence  readily  separable  from 
other  substances  :, 

OTT 
(CH3)2CO  +  S03HNa  =  (CH3)2C<gO  ™-    (sodium  acetonebisulphite). 

3 

This  compound  crystallises  also  with  1  mol.  H20  and  yields  acetone  easily 
when  heated  with  dilute  soda  solution. 

With  hydrocyanic  acid,  ketones  give  the  cyanohydrins  or  nitriles  of  higher 

OTT 

acids  :   e.  g.,  (CH3)2C<CN  . 

With  hydrogen  sulphide,  but  only  in  presence  of  HC1,  etc.,  they  form 
trithioketones,  which  on  heating  give  simple  thioketones. 

With  hydroxylamine,  ketones  readily  form  the  so-called  ketoximes, 
R2C :  N '  OH,1  similar  to  aldoximes,  and  with  phenylhydrazine  they  give 
phenylhydrazones,  just  as  aldehydes  do  : 

(CH3)2CO  +  NH2  •  OH  =  H2O  +  (CH3)2C  :  N  •  OH  (acetoxime). 

Under  certain  conditions,  e.  g.,  by  the  action  of  acetyl  chloride,  ketoximes 
undergo  an  atomic  transposition  by  which  they  are  converted  into  amides 
substituted  in  the  amino-group  (Beckmann  rearrangement),  these  being  tauto- 
meric  with  the  ketoximes  : 

R  •  C  •  R'  R  •  C  :  O 

II  I 

N  •  OH  NHR'. 

The  action  of  nitrous  acid  (or  its  esters)  yields  isonitrosoketones  : 
CH3  •  CO  •  CH3  +  N02H  =  H20  +  CH3  •  CO  •  CH  :  N  •  OH. 

In  presence  of  various  reagents,  e.  g.,  lime,  potash,  sulphuric  or  hydrochloric 
acid,  etc.,  the  ketones  lose  water  and  undergo  condensation  (whilst  aldehydes 
polymerise) :  3(CH3)2CO  =  2H2O  +  C9H14O.  Similar  condensations  occur 
between  ketones  and  aldehydes. 

The  FORMATION  OF  KETONES  takes  place  on  the  dry  distillation  of 
wood  or  of  the  calcium  or  barium  salts  of  many  organic  acids  or  on  simple 
heating  of  the  latter  or  the  anhydrides  of  the  acids  in  presence  of  phosphorus 
pentoxide  :  (CH3  •  C02)2Ca  =  CaCO8  +  CH3  •  CO  •  CH3  (acetone) ;  if  mixed 
ketones  are  required,  a  mixture  of  the  salts  of  two  different  acids  is  used.2 
Noteworthy  also  is  the  formation  of  ketones  by  the  oxidation  of  secondary 

1  For  the  ketoximes  (as  for  the  aldoximes)  stereoisomerides  exist  as  a  consequence  of  the 
stereoisomerism  of  nitrogen  (see  p.  22 )  which  has  been  studied  by  Beckmann,  V.  Meyer,  Auwer, 
H.  Goldschmidt,  Hantzsch  and  Werner,  Mimmni,  etc.     Thus  for  aldoximes  we  have  the  two 
following  stereoisomeric  configurations  : 

R— C— H  R— C— H 

||  (syw-aldoxime)  and  ||         (emto'-aldoxime), 

N— OH    '  OH— N  ' 

whilst  for  ketoximes,  stereoisomerides  exist  if  the  two  alkyl  radicals  are  different : 

R— C— R'  R— C^R' 

(syn-ketoxime)  and  (awfa'-ketoxime) 

N— OH  OH— N 

These  isomerides  are  transformable  one  into  the  other,  and  in  addition  to  their  physical  differ- 
ences exhibit  also  chemical  differences,  e.  g.,  in  regard  to  the  readiness  with  which  they  lose 
water  (aldoximes  giving  nitriles). 

2  This  reaction  may  be  used  to  demonstrate  the  normal  constitution  (absence  of  branching 
from  the  carbon  chain)  of  acids,  ketones,  and  hydrocarbons  (paraffins),  since  on  distilling  an 
organic  barium  salt  with  a  normal  Cn  chain  with  barium  acetate,  a  Cn+j.  ketone  is  obtained 
which  should  also  be  normal,  as  the  methyl  group  of  the  acetate  unites  with  the  carbonyl  at  the 
end  of  the  chain  of  the  acid.     On  oxidation,  this  ketone  gives  a  Cn  -  i  acid  which  will  also  be 
normal.     From  this  are  prepared  the  ketone  and  then  a  Cn  -  2  acid,  so  that  normal  products 
are  always  obtained  (also  the  corresponding  hydrocarbons)  by  this  gradual  descent  from  a  high 
acid  of  which  the  constitution  is  known  to  be  normal. 


254  ORGANIC    CHEMISTRY 

alcohols  (see  p.  125) :  CH3  •  CH(OH)  •  CH3  +  0  =  H2O  -f  CH3  •  CO  •  CH3.  Also, 
with  powdered  metals  (Sabatier  and  $enderens,  pp.  35,  67  and  124),  secondary 
alcohols  give  ketones,  hydrogen  being  eliminated. 

Ketones  are  also  formed  by  the  action  of  water  in  the  hot  on  chlorinated 
hydrocarbons  having  two  chlorine  atoms  united  to  the  same  carbon  atom  : 
(CH3)2CC12  +  KjO  =  2HC1  +  CH3  •  CO  •  CH3. 

Another  general  method  of  preparing  ketones  is  based  on  the  interaction  of 
zinc  alkyls  and  acid  chlorides,  the  additive  product  formed  being  immediately  de- 
composed with  water  in  such  a  way  as  to  avoid  the  formation  of  tertiary  alcohols : 
2CH3  •  CO  •  Cl  +  Zn(C2H5)2  =  ZnCl2  +  2CH3  •  CO  •  C2H5  (methyl  ethyl  ketone). 

Acetone  is  formed  when  acetic  acid  vapour  is  passed  over  a  heated  acetate  or 
basic  oxide. 

ACETONE  (Propanone),  CH3  •  CO  •  CH3,  is  found  in  small  quantities  in  the 
human  organism,  where  it  is  formed  in  larger  amounts  during  certain  diseases 
(diabetes,  acetonuria).  It  is  formed  in  considerable  quantities  in  the  dry 
distillation  of  wood  and  of  other  organic  substances  (calcium  acetate,  sugar, 
gum,  wool-fat,  etc.).  It  is  a  liquid  with  an  ethereal  odour  and  a  characteristic 
burning  taste,  b.-pt.  56-50,1  sp.  gr.  0'7970  at  15°  and  0'7798  at  30°;  it  solidifies 
at  —  95°.  Its  heat  of  evaporation  is  125'3  Cals.  at  56'3° ;  a  litre  of  the  vapour, 
calculated  to  0°  and  760  mm.,  weighs  2'5896  grams.  It  is  soluble  in  water 
(from  which  it  separates  on  addition  of  soluble  salts),  alcohol,  ether,  and 
chloroform;  it  dissolves  fats,  resins,  ethereal  oils,  nitrocellulose,  etc.,  and  is 
readily  inflammable.  It  dissolves  only  0'26  per  cent,  of  paraffin  wax. 

In  aqueous  solution  rendered  alkaline  with  sodium  carbonate,  it  is  oxidised 
with  ease  by  potassium  permanganate,  and  chromic  acid  converts  it  into  acetic 
acid  and  carbon  dioxide.  With  sodium  it  forms  sodium  fi-allyloxide  : 

CH3  •  C(ONa)  :  CH2. 

In  the  crude  form,  it  is  used  in  varnish,  lac  and  colour  factories  and  in  a  more 
or  less  pure  state  in  the  manufacture  of  iodoform.  Also  at  the  present  time 
pure  acetone  is  employed  in  large  quantities  for  gelatinising  the  nitrocellulose 
of  cordite  and  other  smokeless  powders  (see  later :  Statistics),  and  that  of 
celluloid  so  that  this  may  be  rolled.  Large  quantities  are  consumed  in  the 
manufacture  of  varnishes  with  a  basis  of  cellulose  acetate  which  serve  as 
"  dope  "  in  the  construction  of  aeroplanes.  Acetone  is  used  in  making  chloro- 
form and  its  derivatives  and  in  the  preparation  of  plastic  materials  from  casein 
and  copal  resin  (which  gives  a  kind  of  amber);  with  mannitol,  arabitol  or 
glycerine  it  gives  camphor  substitutes  (Ger.  Pat.  214,962).  It  may  be  used 
in  the  synthesis  of  indigo  from  orthonitrobenzaldehyde  and  in  making  isoprene 
for  artificial  rubber.  It  is  employed  to  some  extent  to  dissolve  acetylene  (q.  v. ) 
and  also,  in  the  crude  state,  owing  to  the  intense  burning  taste  it  imparts,  as 
a  denaturant  for  spirit,  from  which  it  cannot  be  separated  by  distillation. 

Industrial  Preparation.  Calcium  acetate  obtained  from  pyroligneous  acid  (which  see) 
is  subjected  to  dry  distillation,  the  temperature  being  controlled  so  that  it  does  not  exceed 
300°;  the  vapours  evolved  are  rapidly  cooled  and  condensed,  giving  crude  acetone.  In 
order  to  avoid  superheating  and  irregularity  during  the  distillation,  moist  calcium  acetate 
is  sometimes  employed.  The  acetone  vapour  escaping  condensation  is  easily  recovered 
by  passing  it  through  towers  down  which  a  spray  of  sodium  bisulphite  solution  falls ;  this 
fixes  the  acetone,  which  may  be  liberated  by  distilling  the  solution  in  presence  of  an  alkali. 
In  France,  Buisine  has  utilised  the  wash-waters  of  dirty  wool  to  prepare  acetone  from  the 

1  The  vapour  pressure  of  acetone  vapour  is  179'6mm.  of  mercury  at  20°,  420  mm.  at  40°, 
860  5  mm.  at  60°,  1611  mm.  at  80°,  2797  mm.  at  100°,  4547  mm.  at  120°,  and  6974  mm.  at  140°. 
The  composition  of  the  vapour  obtained  when  aqueous  solutions  of  acetone  are  boiled  is  as 
follows : 

Percentage  of  acetone  in  solution         1        4       10       20      40      60      80       85      90       95      100 
„     vapour   .    20-4    56    81-5    87-5   92-5    94    95-3.  95-7    96-3    97-5    100 


ACETONE  255 

fat  they  contain.  This  process  has  been  tried  on  an  industrial  scale  at  Roubaix,  but  as  yet 
without  marked  success. 

During  the  European  War  acetone  increased  enormously  in  price — even  to  £400  per 
ton — and  many  different  methods  of  making  it  were  employed.  In  France  and  elsewhere 
it  was  obtained  from  starch  by  the  action  of  special  micro-organisms,  which  produce  at 
the  same  time  large  proportions  of  butyl  alcohol  (now  used  for  making  various  butyl  esters) 
and  higher  ketones.  Synthetic  acetone  is  prepared  also  from  acetylene,  which  with 
energetic  oxidising  agents  (persulphuric  acid,  hydrogen  peroxide,  etc.)  in  presence  of  a 
mercuric  salt  (e.g.,  HgCl2)  gives  first  trichloromercuriacetaldehyde,  C(HgCl)3*OH;  the 
latter,  with  dilute  HC1  in  the  hot,  yields  formaldehyde  and  3HgCl2.  When  passed 
through  a  tube  containing  a  suitable  catalyst  at  400°,  acetic  acid  vapour  yields  acetone : 
2CH3  •  COOH  =  C02  +  H20  -f-  CH3  •  CO  •  CH3. 

The  crude  acetone  is  purified  by  digesting  it  with  quicklime  and  then  distilling  it  from 
sodium  hydroxide  and  subsequently  over  sodium  sulphite. 

STATISTICS  AND  PRICES.  Acetone  is  used  most  largely  for  smokeless  powder,  and 
during  the  European  War  its  consumption  and  price  reached  fantastic  figures.  Italy 
imported  the  following  quantities  of  acetone,  mostly  from  the  United  States : 

1910   1911   1912   1913   1914    1915     1916      1917      1918 

Imports,  hectolitres  .  438  801  325  391  780  3,273  7,253  14,542  26,584 
Value  in  £  .  .  2,628  —  —  6,593  —  52,360  174,080  465,320  850,680 

Great  Britain  consumed  in  1908  1500  tons  of  acetone  (£100,000),  almost  all  imported 
from  the  United  States;  in  1910  1100  tons  (£57,000)  was  imported.  No  certain  figures 
regarding  the  enormous  amounts  imported  during  the  war  are  available,  but  in  1917  the 
quantity  probably  exceeded  10,000  tons,  of  the  value  £4,000,000. 

Germany  imported  crude  acetone,  especially  from  Austria,  and  exported  pure  acetone 
in  the  following  quantities  (tons) : 

1907      1908      1909      1910      1911     1912 

Imports      .      56          87-5        271-5        482          767         912  (£38,800) 
Exports      .    801        357          328  414          468        1012  (£60,000) 

France  produces  acetone  to  some  extent  and  also  imports  it :  2015  tons  in  1913,  1258 
in  1914,  300  in  1915,  and  357  in  1916. 

Crude,  impure  acetone  (acetone  oil)  was  sold  before  the  war  at  £34  per  ton  if  dark,  or 
£40  if  pale.  Acetone  for  industrial  purposes  (85  to  90  per  cent.)  sold  at  £60,  the  pure 
product  (95  to  97  per  cent.)  at  £68,  and  the  chemically  pure  (98  to  100  per  cent.)  at  £80. 
The  bisulphite  compound  is  also  placed  on  the  market  at  £40  per  ton  (or  14s.  per  kilo  if 
chemically  pure). 

Tests  for  Acetone.  These  are  of  especial  importance  for  explosive  factories,  where  a 
highly  purified  product  is  required.  It  should  dissolve  in  water  in  all  proportions  without 
rendering  it  turbid.  When  mixed  with  a  little  0-1  per  cent,  permanganate  solution  it 
should  retain  the  colour  for  some  minutes'.  If  acetone  contains  water,  when  mixed  with 
an  equal  volume  of  light  petroleum  (boiling  at  40°  to  60°)  two  layers  are  formed;  if  no 
water  is  present,  the  liquids  mix  perfectly.  At  least  95  per  cent,  of  it  should  distil  between 
56°  and  56-5°,  and  it  should  not  redden  blue  litmus  paper.  Kramer's  quantitative  iodo- 
metric  test  (see  p.  129)  should  indicate  at  least  98  per  cent,  of  acetone;  Strache's  method, 
in  which  phenylhydrazine  is  employed,  may  also  be  used.1  The  detection  of  acetone  in 
other  substances  is  effected  by  means  of  orthonitrobenzaldehyde  and  caustic  soda,  which 
convert  acetone  into  indigo. 

MESITYL  OXIDE,  CH3  •  CO  •  CH  -.  C(CH3)2,  is  an  aromatic  liquid  boiling  at  132°. 

1  Strache's  method  for  the  indirect  estimation  of  compounds  containing  carbonyl  groups  (aldehydes 
and  ketones).  When  to  a  solution  of  an  aldehyde  or  a  ketone  is  added  an  excess  of  a  phenyl- 
hydrazine solution  of  definite  strength,  the  excess  of  the  latter  which  does  not  combine  may  be 
deduced  from  the  amount  of  nitrogen  liberated  on  decomposing  (oxidising)  in  the  hot  with 
Fehling's  solution  [a  mixture  in  equal  volumes  of  the  following  two  solutions  :  (a)  69-26  grams 
of  air-dried  copper  sulphate  crystals  dissolved  in  water  to  1  litre;  (b)  346  grams  of  Rochelle  salt 
dissolved  in  800  c.c.  of  water  +  105  grams  sodium  hydroxide,  the  whole  made  up  to  1  litre  with 
water] :  C6H5NH  •  NH2  +  0  =  H20  +  C6H6  +  N2.  The  test  is  made  on  0-2  to  0-6  gram  of 
substance  (aldehyde  or  ketone)  and  the  details  of  the  operation  are  described  in  Zeitschr.  fur 
analyt.  Chemie,  1892,  p.  573,  or  in  Hans  Meyer's  "  Determination  of  Radicals  in  Carbon  Com- 
pounds," 1899,  p.  65. 


256  ORGANIC    CHEMISTRY 

PHORONE,  (CH3)2C  :  CH  •  CO  •  CH  :  CMe2,  forms  yellow,  readily  fusible  crystals,  and 
is  obtained  by  saturating  acetone  with  hydrogen  cliloride. 

BUTANONE  (Methyl  ethyl  ketone),  CH3  •  CO  •  C2H5,  is  a  liquid,  b.-pt,  81°,  and  is 
contained  in  wood-spirit. 

KETENES 

These  constitute  a  group  of  substances  discovered  by  Staudinger  since  1905.  Although 
they  contain  the  ketoiiic  group,  CO,  they  differ  markedly  from  the  ketones  in  their  great 
reactivity,  since  they  are  unsaturated  compounds,  that  is,  imsaturated  ketones. 

They  are  derived  from  the  type  R-^C :  CO,  which  was  formerly  thought  incapable  of 
existing  in  the  free  state.  The  residues,  R,  may  be  either  aromatic  or  aliphatic  hydro- 
carbon radicals.  All  these  compounds  may  be  derived  from  KETENE,  CH2  :  CO,  which 
is  a  colourless  gas,  b.-pt.  —56°,  m.-pt.  —151°,  and  was  prepared  in  1908;  it  has  a  disagree- 
able odcrur  (resembling  somewhat  those  of  chlorine  and  acetic  anhydride),  is  poisonous 
and  even  in  small  quantity  produces  intense  headache.  It  is  easily  polymerised  (by 
metallic  chlorides  or  tertiary  bases),  yielding  a  coloured  resin.  It  decolorises  ethereal 
bromine  solutions  instantly,  and,  unlike  disubstituted  ketenes,  does  not  undergo  oxidation 
in  the  air.  The  most  stable  and  best  characterised  of  these  compounds  are  dimethyl-, 
(CH3)2C:CO,  and  diphenyl-ketem,  (C6H5)2C:CO;  monomethyl-,  CH3  •  CH :  CO,  and 
monoethyl-ketene,  C2H6  •  CH :  CO,  have  properties  similar  to  those  of  carbon  tmbo-vide, 
O  :  C :  C :  C :  0,  and  resemble  the  isocyanates  in  their  great  reactivity.  The  disubstituted 
ketenes  are  coloured  and  readily  oxidise  in  the  air ;  two  molecules  condense  with  one  of  a 
base  (pyridine,  quinoline),  and  they  unite  with  the  C:  N  •  group  (benzylideneaniline)  and 
with  the  C :  0  group  (quinones),  forming  /3-lactams  and  /3-lactones.  All  the  ketenes 
combine  with  water,  alcohols,  or  amines  at  the  double  carbon-linking,  giving  compounds 
of  an  acid  nature.  The  monosubstituted  ketenes  are  also  called  aldoketenes  (colourless) 
and  the  disubstituted  ones,  ketoketenes  (coloured).  They  are  usually  prepared  by  the  action 
of  zinc  on  an  ethereal  solution  of  acid  halogen  derivative  with  a  second  halogen  in  the 
a-position  (more  rarely  by  heating  malonic  anhydrides) : 

CH3  •  CHBr  •  COBr  +  Zn  =  ZnBr2  +  CH3  •  CH  :  CO. 

a-bromopropionyl  bromide 

The  ketenes  (especially  ketoketenes)  are  easily  transformed  into  acids,  and  those  that 
condense  (the  ketoketenes)  with  unsaturated  groups  (ethylene  and  carbonyl  compounds, 
Schiffs  bases,  thioketones,  nitroso-  and  azo-compounds)  form  compounds  with  a  closed 
chain  of  four  or  six  carbon  atoms,  these  being  resolved  into  two  unsaturated  compounds 
when  heated.  The  aldoketenes  undergo  polymerisation  more  readily,  giving  derivatives 
of  cyclobutane  which  decompose  on  heating. 

B.  DERIVATIVES    OF   POLYHYDRIC   ALCOHOLS 

The  ethers  of  polyhydric  alcohols  are  generally  prepared  by  the  methods  used  for  ethers 
of  the  monohydric  alcohols  and  have  many  properties  in  common  with  these. 

ETHYL  ETHER  OF  GLYCOL,  OH  •  C2H4  •  OC2H5,  boils  at  127°  and  the  DIETHYL 
ETHER,  C2H4(OC2H5)2,  at  123°.  Of  the  esters  of  glycol,  the  mono-  and  di-acetates, 
C-jH^OCgHgO)^  which  are  liquids  soluble  in  water,  are  well  known.  Glycolchlorohydrin 
or  Monochloro'ethyl  Alcohol,  OH  •  CH2  •  CH2  •  Cl,  boils  at  130°,  is  soluble  in  water  and 
is  prepared  by  passing  hydrogen  chloride  into  hot  glycol.  GLYCOLSULPHURIC  ACID, 
OH  •  C2H4  •  O  •  SO3H,  is  the  sulphuric  ester  of  glycol.  Glycol  Dinitrate,  C2H4(N03)2,  is 
a  yellowish  liquid  insoluble  in  water  and  explodes  on  heating ;  it  is  prepared  by  treating  glycol 
with  nitric-sulphuric  mixture  (see  later  ;  Nitroglycerine).  It  is  readily  hydrolysed  by  alkali. 

ETHYLENECYANOHYDRIN,  CH2  :  C  :  N  •  CH2  •  OH,  is  isomeric  "  with  Ethyl- 
idenecyanohydrin,  CH3  •  CH(OH)  •  CN.  Ethylene  Cyanide,  C2H4(CN}2,  obtained  by  the 
action  of  potassium  cyanide  on  ethylene  bromide,  forms  a  crystalline  mass ;  on  hydrolysis 
it  gives  Succinic  Acid,  C2H4(COOH)2. 

ETHYLENE  OXIDE,  CH2  •  O  •  CH2,  isomeric  with  acetaldehyde,  is  a  liquid  with  an 
ethereal  odour,  sp.  gr.  0-898  (at  0°),  b.-pt.  12-5°;  although  neutral  in  its  reaction  it 
precipitates  certain  metallic  hydroxides  from  solutions  of  their  salts.  It  is  formed  on 
distilling  glycolchlorohydrin  with  potash.  It  reacts  readily  and  dissolves  in  water  with 
gradual  formation  of  glycol. 


T  A  U  R  I  X  E  257 

The  following  compounds  are  also  known :  Ethylene  Monothiohydrate,  C2H4(OH)  •  SH; 
Glycol  Mercaptan  (Ethan-l :  2-dithiol),  C£H4(SH)S;  Dithioglycol  Chloride,  (C^ClJjS,  which 
is  a  very  poisonous  liquid.  Hydroxynuthyl-sulphonic  Add,  CH2(SO3H)  •  OH,  is  solid  and  is 
obtained  from  methyl  alcohol  and  fuming  sulphuric  acid.  Mdhylenedisulphonic  (or 
Methionic)  Acid,  CHjfSOjHjj,  is  formed  from  acetylene  and  fuming  sulphuric  acid,  by  way 
of  Acetaldehydedwulphonic  Acid,  CHO  •  CH.(SOJ3.)y  which  with  lime  gives  formic  acid  and 
methionic  acid ;  the  latter  is  isomeric  with  ethylsulphuric  acid,  but  cannot  be  hydrolysed. 
Hydroxytlhylzul phonic  Acid,  OH  •  CHj  •  CHg  •  SOjH  (Isethionic  Add),  is  a  crystalline  mass 
formed  by  treating  ethyl  alcohol  with  sulphur  trioxide;  ethylene  with  SO3  gives  Carbyl 
Sulphate,  CgH^SO^  which  forms  sulphuric  and  isethionic  acids  with  water. 

Glycol  forms  also  two  amines :  Hydroxyethyiaminc,  OH  •  CjH4  •  XHj  (primary  mono- 
valent  base,  or  HydroxyoJkyl  Base,  or  Hydramine),  and  Ethylenediamine,  C2H4(NH2)2 
(primary  divalent  base).  These  may  also  be  regarded  as  derived  from  one  or  two  molecules 
of  ammonia,  in  which  all  or  part  of  the  hydrogen  is  substituted  by  the  hydroxyethyl  group, 
•  C2H4  •  OH,  or  by  ethylene,  CgHj^.  Thus,  such  compounds  as  the  following  are  known  : 
XH,  C^  •  OH;  (XHj^CjH^  NH(C2H4  -  OHfe,  Dihydroaydiethylamine ;  N(CjH4  •  OH^, 
Trihydroxytriethylamine ;  (NH)2(C2H4)2,  Diethylenediamine  ;  X2(C2H4)S,  Trie&ylenedia- 
mine ;  and  finally  quaternary  bases  containing  alkyl  groups,  e,  g.,  Choline  (or -Bilineurine), 
((•H3).j  i  N(- OH)-('2H4-OH,  or  Hydroxyeihyltrimethylamnumium  Hydroxide,  which  is 
obtained  from  trimethylamine  and  ethylene  oxide  and  is  found  in  the  bile,  in  egg-yolk, 
and  in  the  brain  in  the  form  of  lecithin  (see  later) ;  it  is  not  poisonous,  but  when  oxidised 
with  nitric  acid  yields  Mu&arine,  CH(OH)j  •  CH,  •  NfCHjk  •  OH,  which  has  a  distinct 
poisonous  action.  On  putrefaction,  choline  gives  neurine  (or  Trimethylrinyiammottivm, 
hydroxide),  X(CH3)3(C2H3)  •  OH,  which  is  also  poisonous.  Many  of  these  compounds 
are  formed  in  putrefying  proteins  and  in  dead  bodies,  and  are  called  ptomaines. 

These  bases  are  prepared  by  the  same  methods  as  the  monovalent  bases  (p.  239),  the 
primary  dia mines,  for  example,  being  obtained  by  reducing  the  nitriles,  CBH±Jt(CX)±,  in 
hot  alcoholic  solution  by  means  of  sodium  or  from  ethylene  bromide  and  alcoholic  ammonia 
at  100°.  They  are  liquid  or  solid  substances  and  have  certain  of  the  characters  of  ammonia. 
Pentamethylenediamine  or  Cadaverine,  NH^  •  CHg  -  CHj  •  CH,  •  CH,  -  CHj  •  XH^,  boils  at 
179°  and,  being  a  8-diamine,  can  form  Piper  idine,  C5HUX,  with  separation  of  ammonia. 

Diethylenediamine  or  Piperazine,  C2H4<^^^>CZH4,    melts  at  104°  and  boils  at  146°. 

Teiramethylenediamine  is  called  also  Putrescin£ 

TAURINE  (Aminoethylsulphonic  Acid),  NHj  •  CHj  •  CH2  •  SO3H,  is  found  in  com- 
bination with  cholic  acid  (as  Taurocholic  Acid)  in  the  bile  of  various  animals  and  also 
in  the- lungs  and  kidneys.  It  forms  monoclinic  prisms  soluble  in  hot  water  but  insoluble 
in  alcohol,  and  has  a  neutral  reaction,  the  basic  and  acid  groups  neutralising  one  another. 
It  is  not  hydrolysable. 

Of  the  derivatives  of  Glycerol,  the  Chlorhydrins  or  esters  of  hydrochloric  acid  are  of 
interest ;  they  are  liquids  soluble  in  alcohol  or  ether,  and,  to  a  less  extent,  in  water.  With 
hydrochloric  acid,  glycerol  forms  the  MonocUorhydrin,  C3H5(OH)1C1,  of  which  two 
isomerides  (a-  and  /?-)  are  known,  and  the  Ztichiorhydri*,  C3H5(OH)C12,  also  existing  in 
two  isomeric  forms.  Either  of  these,  when  treated  with  PQj,  gives  the  tricUoro- 
derivative,  CgHjClg.1  At  the  present  time  interest  attaches  also  to  the  forming  and 
acetins,  which  are  used  in  the  manufacture  of  non-congealing  explosives.2 

1  According  to  Ger.  Pat.  180,668,  the  monochlorhydrin  is  made  by  heating  for  fifteen  hours  in 
an  autoclave  at  1203  a  mixture  of  100  parts  of  glycerol  with  150  parts  of  hydrochloric  acid 
(sp.  gr.  1-185).  The  water  is  distilled  off  and  the  residue  subjected  to  fractional  distillation  in  a 
vacuum  (15  mm.  pressure) ;  alter  the  acid  and  water  have  been  eliminated,  the  monochlorhydrin 
distils  over  at  130°  to  150°,  and  the  unaltered  glycerine  at  165°  to  180°.  If  it  is  to  be  nitrated  and 
used  for  explosives,  it  is  sufficient  to  get  rid  of  the  water  and  acid.  According  to  Fr.  Pat,  370,224, 
the  monochlorhydrin  may  also  be  obtained  by  shaking  glycerine  with  the  calculated  quantity 
of  sulphur  chloride  at  a  temperature  of  40°  to  50° ;  the  water  formed  is  distilled  off  in  a  vacuum 
at  60°  to  70°.  The  a-MonocUorhydrin,  CH,C1  •  CH(OH)  •  CH,  •  OH,  is  obtained  (according  to 
Fr.  Pat.  352,750)  by  passing  hydrogen  chloride  into  glycerine  heated  to  70°  to  100°. 

Like  glycerine  itself,  the  chJorhydrins  are  easily  nitrated,  yielding  non-congealing  explosives 
(see  later). 

*  Monoacetin,  CjHj(OH  \(O  •  COCH,),  is  obtained  by  heating  forten  to  fifteen  hours  at  100° 
a  mixture  of  10  parts  of  glycerol  with  15  parts  of  40  to  100  per  cent,  acetic  acid,  the  weak  acetic 
acid  (25  to  30  per  cent.)  that  distils  over  being  condensed  separately.  Ten  parts  of  70  per  cent. 
^OL.  H.  17 


258  ORGANIC    CHEMISTRY 

GLYCIDE  ALCOHOL,  CH2— CH  •  CH2  •  OH,  is  a  liquid,  b.-pt.  162°,  soluble  in  alcohol 

\0/ 

or  ether,  and  also  in  water,  with  which  it  gives  glycerol  again;  with  hydrochloric  acid 
it  gives  the  chlorhydrin.  It  may  be  regarded  as  derived  from  glycerol  by  the  removal  of 
a  molecule  of  water,  and  is  prepared  by  the  separation  of  HC1  from  the  a-monochlorhydrin 
by  means  of  bartya.  It  is  isomeric  with  propionic  acid  and  reduces  ammoniacal  silver 
solution.  Separation  of  hydrogen  chloride  from  the  dichlorhydrin  yields  Epichlorhydrin, 
CH2 — CH  •  CH2C1,  which  may  be  regarded  as  the  hydrochloric  ester  of  glycide  alcohol. 

\o/ 

It  boils  at  117°,  has  an  odour  like  that  of  chloroform  and  is  insoluble  in  water.  It  is 
isomeric  with  propionyl  chloride  and  monochloroacetone,  and  serves  as  a  good  solvent 
for  nitrocellulose,  celluloid,  hard  resins,  organic  dyestuffs,  etc. 

GLYCEROPHOSPHORIC  ACID,  OH  •  CH2  •  CH(OH)  •  CH2  •  O  •  PO(OH)2,  is  optically 
active,  as  also  are  its  calcium  and  barium  salts  (Isevo-rotatory).  It  is  interesting  from  the 
fact  that  when  the  hydroxyl-groups  are  esterified  with  palmitic,  stearic,  or  oleic  acid,  and 
the  phosphoric  residue  united  to  choline,  it  gives  rise  to  the  important  group  of  lecithins, 
which  are  optically  active  : 

OR  •  CH2  •  CH(OR')  •  CH2  •  0  •  PO(OH)  •  0  •  CH2  •  CH2  •  N(CH3)3  •  OH, 

where  R  and  R'  are  fatty  acid  residues. 

Lecithins  are  found  in  the  brain,  yolks  of  eggs,  and  many  seeds  and  are  soluble  in 
alcohol,  and,  to  a  less  degree,  in  ether ;  they  give  salts  with  acids  and  with  bases  and  yield 
solid  compounds  with  chloroplatinic  acid  or  cadmium  chloride.  They  are  saponified  by 
baryta,  with  formation  of  choline,  fatty  acids,  and  glycerophosphoric  acid. 

Of  the  nitric  esters  of  glycerine,  the  most  important  is  trinitroglycerine 
or  glyceryl  trinitrate.,  C3H5(ONO2)3,  which  is  one  of  the  most  powerful 
explosives.  We  shall  hence  study  it  from  the  industrial  standpoint,  first  dis- 
cussing certain  general  notions  concerning  explosives.  The  manufacture  of  the 
latter  constitutes  one  of  the  most  interesting  industries  of  organic  chemistry, 
partly  because  of  the  varied  mechanical  appliances  which  it  requires. 

EXPLOSIVE  SUBSTANCES 

The  name  explosive  substances,  or  explosives,  is  given,  in  general,  to  those 
solid  and  liquid  bodies  which,  under  the  influence  of  heat,  percussion,  electrical 
discharge,  etc.,  are  transformed  instantaneously  and  completely — or  nearly 
so — into  a  gaseous  mass  with  an  enormously  increased  temperature. 

If  the  reaction  takes  place  in  a  closed  space,  the  gases  thus  produced  and 
heated  exert  a  very  considerable  pressure  which  can  be  immediately  trans- 
formed into  mechanical  work,  the  enclosing  substance  and  all  the  surround- 
ing objects  being  shattered  with  great  violence  and  noise.  Such  a  phenomenon 
(or  effect)  constitutes  a  so-called  explosion,  and  if  it  attains  very  great  rapidity 
and  power  it  is  termed  a  detonation.  For  a  constant  quantity  of  gas  produced 
in  an  explosion,  the  effect  will  be  the  greater  the  higher  the  temperature 
developed  in  the  reaction. 

acetic  acid  is  then  added  and  the  weak  acid — up  to  40  per  cent.,  which  distils  at  120°- — collected 
apart.  After  this  the  temperature  is  raised  in  three  hours  to  250°,  the  weak  acid  still  being  kept 
separate.  The  crude  monoacetin  remaining  contains  about  44  per  cent,  of  combined  acetic  acid 
and  about  0-8  per  cent,  of  the  free  acid.  This  acetin  is  soluble  in  water  and  serves  well  for  the 
manufacture  of  explosive  and  non-congealing  nitroacetins  (see  Explosives)  and  for  gelatinising 
the  nitrocellulose  of  smokeless  powders  (Vender,  Ger.  Pat.  226,422,  19C6).  The  diacetin  is 
obtained  by  heating  gtycerine  with  glacial  acetic  acid  at  200°  to  275°;  it  boils  at  280°.  The 
triacetin,  C3H5(0  •  CO  •  CH3)3,  is  found  in  the  seeds  of  Eronymus  eiiropceus  and  is  prepared 
artificially  from  the  tribromhydrin  and  silver  acetate  or  industrially  from  the  diacetin  and 
glacial  acetic  acid  at  250°.  It  boils  at  268°,  has  the  sp.  gr.  1-174  at  8°,  and  is  used  as  a  tanning 
material. 


THEORY    OF    EXPLOSIVES  259 

THEORY  OF  EXPLOSIVES.  The  chemical  reactions  and  physical  phenomena 
of  explosives  are  produced  under  conditions  differing  greatly  from  those  in  which  physical 
and  chemical  properties  of  substances  are  usually  studied.  The  pressures,  temperatures, 
and  velocities  with  which  we  have  to  deal  in  ordinary  phenomena  are  of  a  very  different 
order  from  that  of  the  enormous  pressures  of  the  gases  in  the  interior  of  the  earth's  crust, 
which  are  measured  in  hundreds  of  thousands  or  millions  of  atmospheres.  So  also  the 
temperatures  in  various  stars,  e.  g.,  in  the  sun,  reach  thousands  of  degrees,  and  the  veloci- 
ties of  the  planets  hundreds  of  kilometres  per  second.  The  phenomena  now  to  be  con- 
sidered, although  they  do  not  attain  these  enormous  magnitudes,  still  do  approach  them. 
Indeed,  explosions  give  pressures  of  tens  of  thousands  of  atmospheres,  temperatures  of 
thousands  of  degrees,  and  velocities  (of  projectiles)  of  thousands  of  metres  per  second. 

Almost  all  explosive  substances  contain  oxygen  (furnished  by  chlorates,  nitrates, 
nitro  groups,  etc.),  only  very  few,  such  as  nitrogen  chloride  and  iodide,  and  aniline  ful- 
minate, being  without  it.  Mixtures  of  oxidising  agents  with  readily  combustible  substances 
(sulphur,  carbon,  sugar,  etc. )  are  explosive,  but  they  are  less  powerful  than  those  composed 
of  single  compounds  which  explode  by  themselves.  This  is  because  the  elements  necessary 
for  complete  combustion  are  in  much  greater  proximity,  being  present  in  the  molecule  of 
the  explosive  itself;  examples  of  such  explosives  are  nitroglycerine,  guncotton,  mercury 
fulminate,  picric  acid,  etc. 

The  determination  of  the  theoretical  power  of  an  explosive  requires  a  knowledge  of : 

(a)  the  chemical  reaction  accompanying  the  explosion,  so  that  the  heat  of  the  reaction, 
the  temperature,  and  the  volume  and  relative  pressure  of  the  gases  formed  may  be  deduced ; 

(b)  the  velocity  of  the  reaction.    In  order  to  understand  the  theory  of  explosives,  it  is  indis- 
pensable to  call  to  mind  the  fundamental  principles  of  thermochemistry  and  of  thermo- 
dynamics, for  which  the  reader  is  referred  to  the  brief  account  given  in  Vol.  I.,  pp.  51 
and  54. 

(a)  The  chemical  reaction  is  deduced  from  the  difference  in  composition  between  the 
explosive  and  the  products  resulting  from  the  explosion.     When  there  is  sufficient  oxygen 
in  the  explosive  to  produce  complete  combustion,  the  nature  and  quantities  of  the  gases 
may  be  calculated  a  priori,  and  from  their  heats  of  formation  their  temperature  may  be 
deduced.     The  total  combustion  of  nitroglycerine,  when  exploded  in  a  closed  space,  gives 
the  following  products  (a) :  2C3H5(N03)3  =  6C02  +  5H20  +  3N2  +  0. 

When  there  is  deficiency  of  oxygen,  as  in  guncotton  and  other  substances,  it  is  not  easy 
to  foretell  the  products  of  the  reaction,  as  these  vary  with  the  conditions  in  which  the 
explosion  occurs,  and  usually  several  reactions  take  place  simultaneously.  Further  the 
gases  found  after  the  explosion  of  such  products  are  probably  not  always  those  formed  at 
the  instant  of  the  explosion,  as  at  such  high  temperatures  certain  substances  (H20,  CO2, 
etc.)  may  undergo  dissociation  with  absorption  of  heat.1 

(b)  The  heat  developed  in  the  explosion  is  deduced  by  calculation  from  the  thermo- 
chemical  data  of  the  equation,  but  the  practical  result  is  not  in  accord  with  the  theoretical 
calculation,  since  part  of  the  heat  (25  to  30  per  cent. )  that  should  theoretically  be  developed 
is  transformed  into  mechanical  work,  which  is  what  is  utilised  in  practice.     In  calculating 
theoretically  the  heat  of  explosion,  the  heat  of  formation  of  the  explosive  (from  the  elements  : 
see  p.  25)  is  subtracted  from  the  heat  that  should  theoretically  be  developed  in  the  reaction. 
The  heat  of  explosion  varies,  however,  according  as  it  is  determined  at  constant  volume  or 
at  constant  pressure  ;   in  the  latter  case  the  explosion  of  nitroglycerine,  for  example,  is 
effected  in  the  open  air,  since  then  the  volume  varies,  but  the  pressure  is  only  that  of 
the  atmosphere. 

The  heat  of  formation  of  nitroglycerine  from  its  elements  (see  p.  25)  is  given  by  th 
following  equation  (b) :   C3  +  H5  +  N3  +  O9  =  C3H5(N03)3  +  98  Ca!s. 

The  heat  of  reaction  of   nitroglycerine  may  be  calculated   from  equation  (a)  given 

1  The  following  Table  gives  the  percentage  compositions  of  the  gases  resulting  from  the  normal 
explosion  of  various  explosives  in  the  calorimetric  bomb  : 

CO  C02  O2  CH4  H2  N2 

Nitrocellulose  powder  46-87        16-8          0-08         1-26        20-44       14-9 


Gelatine  dynamites 
Carbonite  . 
Picric  acid 
Trinitrotoluene  . 


34-0  32-68  —  0-75  10-0  21-0 

36-0  19-2  2-8  27-6  14-4 

61-05  3-46  0-34  1-02  13-18  21-1 

57-01  1-93  0-11           —  20-45  18-12 


260  ORGANIC    CHEMISTRY 

above,  from  which  it  is  seen  that  2  mols.  or  454  grams  of  nitroglycerine  yield 
6CO2  +  5H2O  +  3N2  +  O.  The  heat  of  formation  of  6C02  is  6  X  97  =  582  Gals., 
and  that  of  5H2O,  5  X  68-5  =  342-5  Gals.  For  the  nitrogen  and  oxygen  there  is  no 
development  of  heat,  since  they  are  not  combined,  so  that  the  total  heat  of  reaction 
calculated  on  the  gases  formed  in  the  explosion  of  2  gram-mols.  of  nitroglycerine  will 
be  924-5  (i.  e.,  582  -f-  342-5)  Gals.  From  this  must  be  subtracted  the  heat  of  formation 
from  the  elements  of  2  mols.  of  nitroglycerine,  since  on  decomposing  under  these  con- 
ditions of  temperature  the  explosive  first  of  all  liberates  its  atoms,  absorbing  as  much 
heat  as  is  evolved  in  its  formation  from  its  elements  (reaction  b),  i.  e.,  196  (98  X  2)  Gals, 
per  2  mols.  The  atoms  thus  liberated  combine  immediately  to  give  the  gases  which  result 
from  the  explosion,  the  heat  of  formation  of  which  has  already  been  calculated. 

The  true  theoretical  heat  of  explosion  at  constant  pressure  for  454  grams  of  nitro- 
glycerine will  hence  be  728-5  (i.  e.,  924-5  —  196)  Gals.,  or  for  a  kilo,  1603  Gals.  The  heat 
of  reaction  at  constant  volume— the  explosion  occurring  in  a  closed  vessel — is  rather  higher, 
the  heat  corresponding  with  the  expansion  of  the  gas  (see  Vol.  I.,  pp.  27  and  52)  not  being 
absorbed,  as  no  expansion  takes  place ;  theoretically  the  heat  at  constant  volume  is  calcu- 
lated to  be  1621  Gals,  per  kilo.1  Sarrau  and  Vieille,  by  direct  practical  measurements, 
found  the  heat  of  explosion  of  nitroglycerine  at  constant  volume  to  be  1600  Gals.,  which 
confirms  the  accuracy  of  the  calculation. 

With  substances  which  themselves  contain  insufficient  oxygen  for  complete  com- 
bustion during  explosion,  it  is  not  easy  to  calculate  theoretically  the  heat  of  explosion, 
since  the  products  of  the  reaction  are  not  exactly  known;  in  such  cases,  various  direct 
practical  determinations  must  be  made. 

On  the  other  hand,  the  presence  of  C02  alone  and  the  absence  of  CO  in  the  gaseous 
products  of  an  explosion  are  insufficient  to  indicate  an  adequate  amount  of  oxygen  in  the 
explosive,  since  in  certain  cases  (e.g.,  with  trinitrotoluene,  etc.)  carbon  separates  during 
explosion.  If  the  gases  contained  CO  the  effect  of  the  explosion  might  be  greater  than 
if  CO2  were  formed  with  simultaneous  separation  of  inert  carbon. 

The  mechanical  work,  in  kilogram-metres,  yielded  by  an  explosive  is  calculated  by 
multiplying  the  number  of  calories  developed  in  the  explosion  of  1  kilo  of  the  substance 
by  the  mechanical  equivalent  of  heat  (=  425,  see  Vol.  I.,  pp.  51  and  52).  For  various 
explosives  this  mechanical  work  (or  potential  energy)  is  given  in  the  following  Table  : 

Nitroglycerine        .         (1  kilo)  =  1600 Gals.  X  425  =  680,000  kilogram-metres 

Explosive  gelatine  .          .  =1530  „  =650,000 

Dynamite       ...  =  1178  „  =  500,000 

Guncotton     ...  =  1074  „  =  456,000 

Fine  sporting  powder       .  =    849  „  =  360,000 

Potassium  picrate  .         .  =780  „  330,000 

Fulminate  of  mercuiy     .  =403  „  =170,000 

Nitrogen  chloride   .         .  =339  =  144,000 

Owing  to  various  causes,  the  total  theoretical  energy  of  explosives  cannot  be  utilised 
practically;  e.  g.,  the  expansion  of  the  gases  at  the  moment  the  projectile  leaves  the  cannon 
or  gun,  the  friction,  the  heating  of  the  barrel,  etc.,  all  constitute  losses  of  the  useful  effect 
of  the  explosive. 

It  is  not  easy  to  calculate  theoretically  the  temperature  of  the  gases  at  the  moment  of 
explosion,  since  the  specific  heat  of  the  gases  at  such  high  temperatures  cannot  be  deter- 
mined, but  is  certainly  rather  higher  than  the  ordinary  value.  Further,  at  such  tem- 
peratures dissociation  phenomena  occur  which  cannot  be  defined;  these,  however,  lower 
the  temperature,  although  not  greatly,  since  with  the  great  pressures  developed  the  disso- 
ciation is  minimal.  On  the  other  hand,  with  the  means  we  possess,  it  is  not  possible  to 
measure  these  temperatures  directly,  and  only  approximately  can  they  be  determined 
for  black  powder.  In  general,  however,  they  are  very  high  and  in  some  cases  exceed  4000° 

1  For  every  gram-molecule  of  a  substance  passing  from  the  solid  or  liquid  to  the  gaseous 
state,  owing  to  the  new  volume  occupied,  590  small  calories  (Vol.  I.,  pp.  27  and  52)  are  absorbed. 
In  the  explosion  of  2  mols.  of  nitroglycerine,  14-5  mols.  of  gas  (6C02  +  5H20  +  3N2  -f  0)  are 
formed,  and  these,  on  expanding,  will  absorb  14-5  X  590  =  8550  small  calories,  or  8-5  Cals.  per 
454  grams  of  nitroglycerine,  i.  e.,  18  Cals.  per  kilo.  This,  added  to  1603,  the  heat  of  reaction 
at  constant  pressure,  gives  1621  Cals.  as  the  heat  of  reaction  at  constant  volume. 


THEORY    OF    EXPLOSIVES  261 

(for  instance,  by  burning  ballistite  in  the  air,  platinum  with  m.-pt.  1800°  is  easily  melted), 
but  even  these  temperatures,  deduced  indirectly,  are  much  lower  than  those  calculated 
theoretically.1 

The  temperature  of  ignition  does  not  usually  coincide  with  the  temperature  of  explosion, 
since  explosion  is  caused  not  so  much  by  the  temperature  as  by  the  pressure  and  other 
factors  to  be  considered  later;  so  that  for  explosion  to  occur,  special  conditions  (detonators) 
are  necessary.  For  some  substances,  however,  e.  g.,  black  powder,  non-compressed  gun- 
cotton,  etc.,  the  temperature  of  ignition,  given  in  the  following  Table,  is  identical,  or  almost 
so,  with  that  of  explosion  : 

Fulminate  of  mercury    .          .          .  200° 

Non-compressed  guncotton     .          .  220°  to  250° 

Nitroglycerine       ....  218°  (explodes  at  240°  to  250°) 

Black  powder        ....  288° 

There  are  thus  explosives  which  explode  when  merely  ignited  with  a  match  and  others 
which  are  exploded  indirectly  by  means  of  detonators. 

The  volume  of  the  gases  formed  in  the  explosion  may  be  calculated  with  reference  to  0° 
and  760  mm.,  taking  account  of  the  fact  that  at  the  moment  of  explosion  the  water  is 
in  the  state  of  vapour.  In  practice,  however,  it  is  of  more  importance  to  calculate  the 
volume  at  the  temperature  of  explosion,  when  a  knowledge  of  the  gases  formed  is  possible, 
as  is  the  case  with  nitroglycerine,  And,  in  general,  with  explosives  containing  sufficient 
oxygen  for  their  complete  combustion.  It  is,  however,  not  easy  to  calculate  the  volume  of 
gas  formed  by  products  containing  an  insufficiency  of  oxygen,  like  guncotton,  etc.,  with 
which  the  gases  vary  quantitatively  and  qualitatively  according  to  the  type  of  explosion; 
in  such  cases  the  volume  must  be  determined  directly. 

The  volume  of  gases  is  calculated  (see  Vol.  I.,  pp.  26  et  seq.)  by  means  of  the  general 
formula, 

V0(l  +  0-003670 
"«•*  -        ~^p—      —• 

where  Vt  is  the  required  volume  at  the  temperature  of  explosion  t,  V0  is  the  volume  at  0° 
and  760  mm.  pressure  (which  can  be  found  from  the  weight  of  the  gases  formed),  and 
0'00367  is  the  coefficient  of  expansion  for  all  gases.  For  such  high  temperatures  and 
pressures,  however,  the  coefficient  of  expansion  is  rather  higher  than  that  resulting  from 
Gay-Lussac's  and  Boyle's  laws,  but  this  difference  is  compensated  for  by  the  somewhat 
higher  specific  heat  of  the  gas  at  high  temperatures,  in  consequence  of  which  more  than 
the  theoretical  quantity  of  heat  is  absorbed. 

In  any  case,  both  for  volume  and  for  pressure,  use  may  be  made  of  van  der  Waals' 
equation  (see  Vol.  I.,  p.  42),  which  was  modified  for  the  gases  from  explosives  by 
Sarrau.2 

The  pressure  of  the  gas  is  deduced  from  the  general  formula  given  above,  Vt  being 

1  Indeed,  water- vapour,  formed  from  H2  +  0,  should  have  theoretically  the  temperature 
7927°  (see  Calculation,  Vol.  I.,  p.  465),  but  in  the  most  favourable  practical  conditions  the  oxy- 
hydrogen  flame  does  not  exceed  2500°.     For  carbon  dioxide  the  heat  of  formation  is  97,000  cals., 
and  the  specific  heat  0-217,  so  that  for  44  grams  of  C02  gas  (gram-mol.)  the  temperature  attain- 
able would  be  ~rr —    r^ys  =  10,160°,  and  allowing  for  the  fact  that  along  with  the  6  mols.  of 

44  /x  U'^il  / 

C02  and  5  of  H20,  the  3  mols.  of  N2  and  half  a  mol.  of  oxygen  formed  in  the  explosion  of  nitro- 
glycerine are  also  to  be  heated  the  theoretical  temperature  of  the  gases  from  the  explosion 
would  be  about  7000°.  This  theoretical  temperature  is  determined  in  general  by  the  formula 

t  =  ,  ,  ,  .  Tr^t,  where  p,  p',  p"  .  .  .  are  the  weights  of  the  gases  formed  in  the  ex- 
plosion, s,  s',  s"  .  .  .  their  specific  heats,  and  C  the  total  heat  in  calories. 

2  Clausius  replaced  the  van  der  Waals  equation   by  the  following  more  exact  expression  : 
RT  f(T) 

p  =  -— ,  ~ir  ~\z»  where  f(T)  denotes  a  decreasing  function  of  the  temperature  T  and  7  is  a 

constant.     Sarrau  rendered  the  value  of  f(T)  definite  by  making  it  equal  to  K~S.~T,  where  2  and 
K  are  two  new  constants.     For  explosion  gases  at  a  very  high  temperature  and  relatively  small 
volume,  the  second  term  of  the  equation  is,  according  to  Sarrau,  negligible,  so  that  there  remains 
RT 


262  ORGANIC    CHEMISTRY 

diminished  by  the  volume  v  of  the  mineral,  non-gasifiable  residue  (in  the  case  of  dynamite 
or  other  mixtures),  so  that : 

V0(\  +  0-00367  t) 
Vt-v 

with  nitroglycerine,  guncotton,  etc.,  v  =  0.  P  is  the  maximum  theoretical  force  of  an 
explosive,  starting  from  its  volume  (solid)  at  the  ordinary  temperature,  but  the  effect  of 
a  given  explosive  will  be  the  greater  as  its  density  increases,  that  is,  the  greater  the  weight 
for  the  same  volume;  for  guncotton,  for  example,  the  effect  will  be  the  greater  for  the 
same  volume,  the  more  it  is  compressed.  Thus  the  relative  specific  gravities  of  different 
explosives  are  of  importance,  and  in  fact  fulminate  of  mercury,  which  has  a  high  specific 
gravity  (five  times  that  of  ordinary  powder  and  three  times  that  of  nitroglycerine),  has 
a  maximum  rapidity  of  reaction  and  is  the  most  powerful  detonator,  being  capable  of 
exerting  a  force  of  about  27,000  kilos  per  square  centimetre  (atmospheres),  this  being  about 
treble  that  given  by  any  other  known  explosive. 

In  practice,  pressures  higher  than  any  imaginable  may  be  attained  when  the  volume 
occupied  by  a  given  weight  of  explosive  in  a  closed  vessel  is  less  than  the  critical  volume  of 
the  gas  developed,  since  this  critical  volume  (Vol.  I.,  p.  28)  cannot  be  diminished  by  any 
pressure,  however  great.  If  we  term  charging  density  the  ratio  between  the  weight  of  the 
explosive  in  grams  and  the  volume  in  cubic  centimetres  occupied  by  it  in  absolutely  filling 
its  envelope  (as  though  it  were  liquid  or  fused),  this  charging  density  corresponds  with  the 
specific  gravity  of  the  explosive;  if  this  density  equals  or  exceeds  the  reciprocal  of  the 

limiting 'volume  [-)  into  which  the  gases  developed  (critical  volume)  can  be  compressed, 

the  pressure  attained  will  be  infinitely  great  and  will  rupture  any  enclosing  vessel,  no 
matter  how  resistant  it  may  be.  The  reciprocal  of  the  critical  volume  of  the  gases  pro- 
duced in  the  explosion  is  termed  the  critical  specific  volume  (or  limiting  density),  and 
comparison  of  this  with  the  density  of  charge  leads  to  consequences  of  practical  importance. 

Limiting  density  Specific  gravity  of 

of  the  gases  the  explosive 

Black  powder   ....     2-05  1-75 

Nitroglycerine.         .         .         .     1-40  1-60 

Powdered  guncotton           .         .1-16  1-20 

Picric  acid        .         .         .         .1-14  1-80 

Fulminate  of  mercury        .         .     3-18  4-42 

Thus,  black  powder  has  a  charging  density  (or  specific  gravity)  of  1-75  to  1-82,  which 
does  not  reach  the  limiting  density,  so  that  even  if  it  is  exploded  in  its  own  volume  it  does 

not  break  the  envelope  if  the  latter  is  strong  enough  to 
withstand  the  pressure  developed,  namely,  about  29,000 
kilos  per  square  centimetre.  For  granular  powder,  the 
density  of  which  is  1,  the  pressure  is  only  6000  kilos. 
FIG.  182.  The  real  density  (specific  gravity)  of  compressed  gun- 

cotton  is  1-2,  that  of  nitroglycerine  1-6,  and  that  of 

picric  acid  1-8,  all  of  these  being  superior  to  the  limiting  densities  of  the  corresponding 
gases ;  so  that  when  they  explode  in  their  own  volume,  all  of  these  explosives  burst  the 
most  resistant  envelope,  and,  in  such  cases,  the  velocity  of  the  explosive  wave  becomes 
infinitely  great.  Fulminate  of  mercury,  although  it  has  the  high  limiting  density  3-18 
(owing  to  the  low  critical  volume,  v),  has  the  specific  gravity  4-42  (to  which  the  density  of 
charge  approximates)  and  behaves  like  nitroglycerine,  etc. 

As  it  is  difficult  to  calculate  a  priori  the  pressures  exerted  by  explosives,  it  is  preferable 
to  determine  them  relatively  by  measuring  certain  effects  of  the  gases  at  the  instant  of 
explosion;  this  is  done,  for  instance,  by  observing  the  crushing  or  deformation  of  small 
cylinders  of  copper  or  lead,  which  are  termed  crushers  (Fig.  182). 

The  total  pressure  depends  on  the  character  of  the  explosive  and  on  the  nature  of  the 
explosion  (see  later),  but  more  especially  on  the  density  of  charge. 

The  specific  pressure  of  an  explosive  is  a  constant  (a),  given  by  the  ratio  of  the  pressure 

(p)  to  the  corresponding  density  of  charge  (d)  of  the  explosive  itself  :  a  —  ^.     This  specific 


VELOCITY    OF    EXPLOSION  263 

pressure  a  is  characteristic  of  any  explosive  and  expresses  the  pressure  developed  by  unit 
weight  (1  gram)  of  an  explosive  in  unit  volume  (1  c.c. ).  The  specific  pressure  is  not  always  the 
maximum  pressure  that  can  be  exerted,  this  depending,  as  we  have  seen,  on  the  charging 
density  in  its  relation  to  the  critical  volume. 

Velocity  of  reaction  or  explosion.  The  duration  of  the  explosion  is  of  great  importance, 
since  on  it  depends  the  greater  or  less  utility  of  the  explosive  for  different  purposes.  The 
more  rapid  the  explosion  the  better  is  the  heat  developed  utilised,  so  that  this  may  be 
used  almost  entirely  in  heating  and  expanding  the  gases  and  so  increasing  the  pressure 
considerably.  If,  however,  the  reaction  is  slow,  a  large  portion  of  the  heat  is  dissipated 
by  radiation  and  conduction. 

Explosives  with  an  extremely  rap.'d  reaction  produce  special  effects,  as  they  shatter 
the  envelope  or  rock  in  immediate  contact  with  the  explosive  into  minute  fragments — 
an  effect  often  not  desired.  These  are  termed  shattering,  percussive  or  high  explosives  and 
their  properties  are  utilised  in  certain  cases,  as,  for  example,  where  a  small  cavity  is  to 
be  made  in  a  rock  so  that  a  large  quantity  of  a  progressive  or  propulsive  explosive  may  be 
subsequently  introduced. 

If  the  reaction,  although  rapid,  is  not  instantaneous,  the  explosion  produces  other 
effects,  for  instance,  the  cleaving  of  large  stones  or  rocks  and  the  projection  of  fragments 
lying  near  the  explosive ;  this  progressive  or  rending  action  is  the  effect  usually  desired 
by  miners.  So  also  progressive  explosives  are  used  for  charging  guns  which  throw 
projectiles. 

According  as  the  gasification  takes  place  more  or  less  instantaneously  (the  one  or  the 
other  effect  may  be  obtained  with  the  same  substance  by  adding  inert  materials  to,  say, 
dynamite,  or  mixing  paraffin  wax  with  guncotton),  explosives  are  more  or  less  shattering. 
Thus,  panclastite  (N204  +  CS2)  and  fulminate  of  mercury  are  more  shattering  than  gun- 
cotton,  the  latter  more  than  dynamite  and  nitroglycerine,  and  this  more  than  smokeless 
powder,  which  is  a  progressive  explosive. 

Many  substances  explode  only  with  detonators  (of  fulminate  of  mercury)  and  the 
cause  of  the  explosion  in  such  cases  is  not  only  the  high  temperature  produced  by  the 
explosion  of  the  detonator,  but  more  especially  the  great  immediate  pressure  resulting 
from  the  instantaneous  production  of  gas,  this  pressure  and  the  sudden  shock  provoking 
the  decomposition  of  the  molecules  of  the  explosive  (Berthelot,  Abel,  Vieille).  The 
duration  of  explosion  or  of  gasification  of  the  detonator  is  500  times  less  than  that  of  the 
explosive  material,  and  the  greater  relative  amount  of  heat  developed  in  a  certain  time  by 
detonators  explains  their  greater  shattering  power  compared  with  that  of  progressive 
explosives.  The  duration  of  reaction  for  detonators  is  only  about  T^V^  of  a  second,  the 
extraordinary  effect  of  these  explosives  being  due  to  the  enormous  amount  of  energy 
developed  (1600  Gals,  for  nitroglycerine)  in  this  short  time  and  in  the  small  space  containing 
them.1 

As  has  been  already  stated,  the  shattering  effect  of  a  substance  is  rendered  evident  by 
exploding  a  few  grams  of  it  on  a  cylinder  of  metal  (crusher)  and  the  actions  of  different 
explosives  are  compared  by  means  of  these  deformed  and  disfigured  crushers.  Fig.  183  B 
shows  a  leaden  cylinder  before  the  explosion,  whilst  A  shows  the  same  cylinder  after  10 
grams  of  dynamite  (a  progressive  explosive)  has  been  exploded  on  it  and  C  the  result 
of  the  explosion  of  10  grams  of  panclastite  (from  nitrotoluene). 

One  and  the  same  explosive  substance  may  be  made  to  give  either  a  shattering  or  a 

1  The  velocity  of  combustion  (or  of  deflagration]  is  sharply  distinguished  from  the  velocity  of 
the  explosive  reaction  and  is  made  use  of  in  certain  cases,  e.  g.,  in  the  throwing  of  projectiles 
(expansive  and  progressive  action).  The  velocity  of  combustion  of  explosives  depends  on,  and 
increases  with  increase  of,  the  pressure  at  which  they  decompose.  Another  factor  influencing 
the  mode  of  combustion  of  explosives  is  the  maximum  velocity  with  which  the  pressure  develops. 

The  exponent  of  the  power  of  the  pressure,  which  admits  of  passing  from  one  value  to  the  other 
in  the  increase  of  the  pressure,  is  called  the  modulus  of  progressivity,  and  serves  to  characterise 
the  various  explosives.  Thus,  this  modulus  varies  from  1-25  to  1-50  for  black  powders  and  from 
1-86  to  1-87  for  smokeless  powders,  whilst  that  of  picric  acid  is  2-82  and  that  of  Favier's  explosive 
(12  per  cent,  of  dinitronaphthalene  +  88  per  cent,  of  ammonium  nitrate)  3-25.  As  will  hence 
be  seen,  these  last  two  explosives  have  the  dangerous  property  of  furnishing  accidental  super- 
pressures,  owing  to  undulatory  phenomena  which  always  accompany  the  combustion  of  sub- 
stances inflammable  with  difficulty.  In  smokeless  powders,  the  moderate  progressivity  com- 
pared with  the  great  power  constitutes  a  valuable  safeguard  in  their  use  in  firearms ;  in  this 
they  are  surpassed  only  by  black  powders,  which  are,  however,  much  less  powerful. 


264 


ORGANIC    CHEMISTRY 


progressive  effect  by  varying  the  velocity  of  the  reaction,  this  usually  depending  on  the 
power  of  the  initial  shock  which  causes  the  explosion  and  on  the  physical  condition  of  the 
explosive.  The  greater  the  density  of  the  latter  the  less  shattering  it  is ;  thus  gelatinised 
guncotton  is  less  shattering  than  the  compressed  cotton  and  this  less  so  than  the  powdered 
cotton  (see  preceding  page). 

The  more  powerful  the  initial  shock  the  greater  is  the  amount  of  kinetic  energy  trans- 
formed into  heat  and  hence  the  higher  the  temperature  developed;  therefore,  also,  the 
greater  is  the  pressure  of  the  resultant  gases  and  the  more  rapid  and  powerful  the  effect 
of  the  explosive.  The  effects  vary  considerably  with  the  manner  in  which  the  explosion 
is  induced;  thus,  if  a  flame  is  brought  near  to  non- compressed  guncotton,  the  latter  burns 
rapidly  but  does  not  explode,  whilst  if  it  is  compressed  and  subjected  to  the  action  of  a  cap 
(detonator)  of  fulminate  of  mercury,  a  real  and  very  powerful  explosion  occurs;  similar 
phenomena  are  observed  with  nitroglycerine  and  dynamite.1 

DETERMINATION  OF  THE  EXPLOSION.  In  order  to- induce  the  explosive  reaction 
of  a  substance,  it  is  sufficient  to  bring  it  at  a  single  point  to  a  certain  initial  decomposition 
temperature  (by  percussion,  detonation,  etc.),  the  sharp  decomposition  at  this  point  then 
producing  a  new  shock  which  heats  the  neighbouring  points  to  the  decomposition  tempera- 
ture, and  so  on,  the  explosion  being  thus  communicated  to  the  whole  mass  by  a  true 
explosive  wave,  which  is  enormously  more  rapid  than  simple  burning.  From  this  will 
be  understood  the  great  importance  of  detonators,  which  do  not  serve  merely  for  ignition ; 

the  difference  will  also  be 
apparent  between  an  ordinary 
explosion  by  ignition  and  per- 
cussion and  that  induced  by 
fulminate  of  mercury  deton- 
ators. 

When  the  phenomenon  of 
explosion  is  studied  more 
closely,  it  becomes  evident 
that  the  gases  produced  at  the 
point  of  ignition  tend  to  expand 
and  hence  to  diminish  the 
pressure  at  that  point  and  also  the  rapidity  of  explosion,  but  if  this  initial  expansion  is 
impeded  the  pressure  and  hence  the  velocity  of  decomposition  increase  rapidly.  In 
practice  miners  obtain  this  effect  by  filling  the  cavity  containing  the  explosive  with  a 
tamping  of  earth  or  stone.  The  same  end  may  also  be  attained  by  increasing  considerably 
the  mass  of  the  explosive  and  the  surface  of  ignition,  and  this  explains  why  certain  sub- 
stances burn,  without  exploding,  in  small  quantities  (guncotton,  nitroglycerine,  etc.),  or 
when  the  ignition  is  confined  to  a  limited  area,  whilst  a  powerful  explosion  may  occur 
when  a  large  quantity  of  explosive  is  used  or  when  it  is  surrounded  by  a  source  of 
considerable  heat. 

1  The  percussive  force  (kinetic  energy)  of  an  explosive  serves  best  to  establish  the  shattering 
power  and  is  calculated  by  C.  E.  Bichel  by  means  of  the  formula  ~2,  where  m  denotes  the  mass 

of  the  gases  formed  in  the  explosion,  or  the  weight  of  the  explosive  divided  by  9-81,  and  v  is  the 
velocity  of  detonation  (i.  e.,  the  time  elapsing  from  the  beginning  of  the  explosion  to  its  com- 
pletion throughout  the  whole  mass).  For  1  kilo  of  an  explosive  gelatine  (92  per  cent,  of  nitro- 
glycerine and  8  per  cent,  of  collodion  cotton)  with  the  charging  density,  1-63,  Bichel  gives  a 
velocity  of  detonation  of  7700  metres  per  second,  so  that  the  percussive  force  in  absolute  units 

1  X  77002 
wil1  be  :     Q.gl  x  2   ~  3'021'916  kilogram -metre-seconds ;   for  black  powder   (with  a  charging 

density  1-04)  exploded  under  the  same  conditions  in  a  closed  vessel  with  a  detonating  cap,  the 
velocity  of  detonation  is  300  metres  per  second,  so  that  ^  *  =  4587  kilogram -metre- 

seconds  ;  for  kieselguhr  dynamite  (75  per  cent,  nitroglycerine)  the  velocity  of  detonation  is  6818, 
and  hence  the  percussive  force,  2,369,272  kilogram -metres  per  second ;  for  a  gelatine- dynamite 
(63-5  per  cent,  nitroglycerine,  1-5  per  cent,  collodion  cotton,  27  per  cent,  sodium  nitrate,  8  per 
cent,  wood  meal),  with  a  charging  density  of  1-67,  the  velocity  of  detonation  is  7000  and  the 
percussive  force  2,497,452;  for  trinitrotoluene,  with  a  charging  density  of  1-55,  the  velocity  was 
7618,  and  the  percussive  force  2,957,896 ;  guncotton,  with  a  charging  density  of  1-25,  had  a  velocity 
of  6383,  the  percussive  force  being  2,076,589;  and  picric  acid,  with  a  charging  density  of  1-55, 
gave  the  velocity  of  detonation  8183,  and  the  percussive  force  3,412,920  kilogram -metre-seconds. 


FIG.  183. 


EXPLOSION    BY    INFLUENCE  265 

For  shattering  explosives  (e.  g.,  fulminate  of  mercury)  no  tamping  is  used,  since  the 
reaction  is  so  rapid  that  the  atmospheric  pressure,  that  is,  the  air  itself  with  its  inertia, 
is  sufficient  to  maintain  the  pressure  of  the  gases.  Even  fulminate  of  mercury,  if  ignition 
is  effected  by  an  electric  contact  (which  heats  a  platinum  wire  to  redness)  and  under  an 
evacuated  bell-jar,  burns  without  exploding,  thus  confirming  the  tamping  action  of  the 
air  in  the  case  of  detonators  and  even  of  ordinary  explosives ;  in  fact,  if  a  roll  of  dynamite 
is  exploded  on  a  bridge,  the  latter  is  cut  in  two  owing  to  the  tamping  action  of  the  air. 

The  explosive  wave  produced  in  the  explosion  of  gaseous  mixtures  and  of  liquids  and 
solids  is  only  slightly  related  to  waves  of  £ound.  The  latter  is  transmitted  from  crest  to 
crest  with  but  little  kinetic  energy,  with  a  small  excess  of  pressure  and  with  a  velocity 
depending  only  on  the  nature  of  the  medium  in  which  it  is  propagated  and  of  equal  magni- 
tude for  vibrations  of  all  kinds,  the  intensity  diminishing  in  proportion  to  the  square  of 
the  distance  from  the  origin.  The  intensity  of  the  explosive  wave,  on  the  contrary,  remains 
constant,  as  it  propagates  the  chemical  transformation  through  the  mass  of  the  explosive 
substance,  communicating  from  point  to  point  of  the  decomposing  system  an  enormous 
amount  of  potential  energy  and  a  great  excess  of  pressure.  The  sound-wave  is  propagated 
in  a  mixture  of  hydrogen  and  oxygen  with  a  velocity  of  514  metres  per  second  at  0°,  but 
the  velocity  of  the  explosive  wave  or  chemical  wave  in  the  same  mixture  (exploded  at  a 
point)  is  2841  metres. 

The  velocity  of  propagation  of  the  explosive  wave  depends  on  the  chemical  nature  of 
the  explosive,  on  the  volume  it  occupies  (hence  on  the  density),  and  on  the  reaction  of 
decomposition;  the  last  determines  the  intensity  of  the  wave  and  depends  on  the  initial 
shock.  Consequently  different  effects  may  be  obtained  from  one  and  the  same  explosive 
by  varying  the  cap  (or  detonator  :  see  later),  and  if  the  latter  is  weak  or  insufficient  the 
explosion  is  only  partial  or  amounts  to  a  simple  deflagration,  thus  causing  loss. 

With  guncotton,  the  velocity  of  this  wave  varies  from  3800  to  5400  metres  per  second 
according  to  the  compression  or  density;  with  nitroglycerine  it  is  1300,  with  dynamite 
2700  to  3600,  with  explosive  gelatines  as  much  as  7700,  with  picric  acid  6500  to  8000, 
with  nitromannitol  7700,  and  with  trinitrotoluene  7200  metres  per  second.  This  velocity 
depends  only  on  the  nature  of  the  explosive  and  not  on  the  pressure,  but  i,t  varies  to  some 
extent  with  the  nature  of  the  envelope.  For  instance,  in  a  rubber  tube  having  a  thickness 
of  3-5  mm.  and  an  internal  diameter  of  5  mm.  and  covered  with  cloth,  ethyl  nitrate  gives 
a  velocity  of  1616  metres,  whilst  in  glass  tubes  of  various  diameters  and  thicknesses  the 
value  is  1890  to  2480  metres.  The  propagation  of  the  explosive  wave  bears  no  relation  to 
that  of  ordinary  combustion  (which  is  much  slower).  The  former  occurs  when  the  inflamed 
gaseous  molecules  acquire  the  maximum  velocity  or  energy  of  translation,  i.  e.,  act  with 
the  whole  of  the  heat  developed  in  the  chemical  reaction. 

Explosion  by  Influence.  If  dynamite  cartridges  are  arranged  in  a  long  row  on  a  flat 
solid  at  distances  of  30  cm.  or  on  a  metal  disc  at  a  distance  of  70  cm.,  explosion  of  the  first 
with  a  fulminate  cap  results  in  the  rapid  and  successive  explosion  of  the  remaining  ones 
simply  by  influence  and  without  the  need  of  detonators  or  fuses.  Air  does  not  conduct 
the  wave  of  explosive  influence  as  well  as  solids,  and  if  the  cartridges  are  suspended  in  the 
air  by  wires  such  explosion  by  influence  does  not  occur.  Water  conducts  the  explosive 
wave  to  a  certain  distance,  but  the  influence  gradually  diminishes  with  increasing  distance 
from  the  centre  of  explosion.  There  have  been  cases  in  which  the  shock  of  a  large  charge  of 
guncotton  has  exploded  neighbouring  torpedoes;  to  avoid  these  inconveniences,  so-called 
safety  explosives  are  now  used  (see  later),  or  the  explosives  are  rendered  less  sensitive  by 
gelatinising  them  or  by  mixing  them  with  various  substances,  such  as  camphor,  paraffin 
wax,  etc. 

These  explosive  waves  are  first  propagated  through  the  explosive  itself,  not  by  a  single 
shock — which  would  gradually  weaken  as  it  advanced — but  by  a  very  rapid  series  of  such 
shocks  produced  by  the  propagation  of  the  explosion  from  point  to  point  of  the  whole  mass 
of  the  explosive,  the  kinetic  energy  being  thus  regenerated  along  the  whole  course  of  the 
wave  in  the  exploding  substance. 

An  explosive  wave  is  thus  distinguished  from  an  ordinary  sound-wave  by  the  fact 
that  the  latter  becomes  enfeebled  as  it  advances,  whilst  the  former  is  characterised  by  the 
uniformity  of  the  energy  transmitted  from  point  to  point  by  a  series  of  numerous  and 
successive  explosions  throughout  the  exploding  mass.  Only  the  last  of  these  explosions 
is  transmitted  with  its  energy  to  the  surrounding  air  and  to  the  matter  on  which  the 


266  ORGANIC    CHEMISTRY 

explosive  rests,  and,  since  it  is  no  longer  reinforced  (by  other  shocks),  it  weakens  as  it 
becomes  more  remote.  Hence  explosion  by  influence  is  not  due  to  the  fact  that  the  distant 
explosive  transmits  or  propagates  the  explosive  wave  through  its  own  mass,  but  is  owing  to 
the  arrest  and  transformation,  at  the  point  of  impact,  of  the  mechanical  energy — it  being 
capable  of  similar  (but  not  of  all)  waves — into  heat  energy,  able  to  cause  decomposition 
and  explosion  of  the  substance  itself.  For  a  long  time  it  was  thought  that  nitrogen  iodide 
could  be  exploded  by  the  simple  note  la  struck  by  a  musical  instrument ;  this  idea  is  now 
contested,  but  it  is  certain  that  some  substances,  on  exploding,  cause  only  the  note  la  of 
the  scale  to  vibrate. 

The  effects  of  large  charges  of  dynamite  (25  to  1000  kilos)  when  freely  exploded  are 
dangerous  to  buildings  and  to  life  for  a  distance  of  500  metres  and  are  felt  as  far  away  as 
3  kilometres  (L.  Thomas,  1904). 

Certain  explosives  decompose  gradually  under  the  action  of  ultra-violet  rays. 

CLASSIFICATION  'OF  EXPLOSIVES.  Explosives  are  to-day  so  numerous  and  are 
prepared  from  such  different  mixtures  and  serve  such  a  variety  of  purposes  that  a  rigorous 
or  rational  classification  is  difficult  or  impossible.  Also  with  a  large  number  of  classes 
there  would  be  many  substances  which  might  belong  to  more  than  one  of  them. 

It  will  hence  be  preferable  to  limit  ourselves  to  a  description  of  the  various  explosives 
without  any  prearranged  classification.  They  will  be  taken  in  the  following  order  :  ( 1 ) 
Black  powder;  (2)  Nitroglycerines  and  dynamites;  (3)  Nitrocellulose;  (4)  Smokeless  or 
progressive  powders;  (5)  Shattering  explosives  (aromatic  nitro-derivatives  and  picrates)  ; 
(6)  Explosives  of  the  Sprengel  type;  (7)  Chlorate  and  perchlorate  powders;  (8)  Safety 
explosives;  (9)  Detonating  explosives  and  caps ;  (10)  Various  explosives. 

BLACK   POWDER   (GUNPOWDER) 

This  explosive,  which  was  the  first  to  be  employed  in  firearms,  and  was  the  only  one 
available  for  military  and  industrial  purposes  until  after  the  middle  of  the  nineteenth 
century,1  has  latterly  become  relatively  unimportant  owing  to  the  discovery  of  dynamite 
and  smokeless  powders. 

Ordinary  black  powder  is  a  mixture  of  potassium  nitrate,  sulphur,  and  carbon  in  vary- 
ing proportions  according  to  the  purpose  for  which  it  is  required.2 

For  black  military  powders,  used  in  guns  and  cannon  in  Italy,  France,  England,  Russia, 

1  It  is  stated,  but  without  any  real  confirmation,  that  the  Chinese  knew  of  gunpowder  as 
early  as  the  first  century  of  the  Christian  era,  and  that  they  used  it  for  throwing  projectiles ; 
more  certain  is  it  that  they  employed  mixtures  of  sulphur,  nitre,  and  carbon  to  make  rockets. 

Also  the  ancient  Indians  used  powders  for  the  preparation  of  a  kind  of  artificial  fire.  Greek 
fire,  used  in  Greece  in  the  seventh  century,  was  obtained  with  explosive  powder  and  probably 
originated  in  China.  The  Arabs  were  acquainted  with  inflammable  mixtures  from  very  remote 
times,  whilst  true  gunpowder,  containing  sulphur,  carbon,  and  nitre,  was  prepared  by  them  only 
in  the  thirteenth  century,  probably  after  they  had  learnt  the  manufacture  from  the  Chinese. 
They,  however,  studied  its  propulsive  properties  and  constructed  the  first  primitive  guns. 

In  Germany  it  is  stated  that  it  was  the  monk  Berthold  Schwarz  (a  native  of  Freiburg,  where 
a  monument  is  now  erected  to  him)  who  recognised  the  power  of  gunpowder  in  about  1310  and 
used  it  for  the  first  time  in  Europe  in  firearms ;  so  that  the  discovery,  not  of  the  powder,  but 
of  guns  for  throwing  projectiles,  is  due  to  Schwarz.  After  the  middle  of  the  fourteenth  century, 
gunpowder  came  into  use  in  Germany,  then  in  Sweden,  Russia,  and  elsewhere  for  guns  and 
cannons.  Macchiavelli  records  that  by  1386  the  Genoese  and  Venetians  had  learnt  from  the 
Germans  the  use  of  powder  with  guns.  According  to  Libri,  cannons  were  made  at  Florence  as 
early  as  1326.  The  projectiles  were  made  first  of  stone,  then  of  stone  covered  with  iron ;  leaden 
shot  began  to  be  used  in  1347,  and  in  1388  Ulrich  Beham  cast  the  first  iron  shot,  which  became 
general  in  the  fifteenth  century.  The  mixing  of  the  ingredients  to  make  the  powder  was  first 
carried  out  by  hand,  and  it  was  only  in  1525,  in  France,  that  powders  were  graded  and  granu- 
lated, the  mixing  being  effected  in  vertical  mills  like  those  used  for  expressing  oil  from  olives. 

2  After  a  series  of  experiments  in  Brussels  in  1560,  the  best  proportions  for  the  ingredients 
were  found  to  be  :   nitre,  75  per  cent. ;   carbon,  15-62  per  cent. ;   and  sulphur,  9-38  per  cent. 
A  thirteenth-century  manuscript  states  that  the  Arabs  used  74  per  cent,  nitre,  15  per  cent,  carbon, 
and  11  per  cent,  sulphur.     A  black  powder  dating  from  1627  and  discovered  in  1905  during 
excavation,  contained  40  per  cent,  nitre,  24  per  cent,  sulphur,  and  37  per  cent,  carbon.     In 
1800  Berthollet  recommended  as  the  most  effective  proportions  :  80  per  cent,  of  nitre,  15  per  cent, 
of  carbon,  and  5  per  cent,  of  sulphur.     Berthelot  has  recently  calculated  the  theoretically  best 
proportions  to  give  a  maximum  development  of  heat,  his  results  being  :  84  per  cent,  nitre  +  8  per 
cent,  sulphur  +  8  per  cent,  carbon ;   this  calculation  assumes  that  the  reagents  are  chemically 
pure,  which  in  practice  is  not  the  case,  and  that  the  fineness  and  mixing  of  the  ingredients  are 
perfect. 


GUNPOWDER  267 

China,  and  the  United  States,  the  maximum  power  is  obtained  without  an  excessive  rapidity 
of  explosion  (so  as  not  to  injure  the  gun  too  much)  with  75  per  cent,  of  potassium  nitrate, 
15  per  cent,  of  carbon,  and  10  per  cent,  of  sulphur,  the  density  being  increased  by  compress- 
ing and  polishing  the  grains;  in  Germany  the  proportions  used  are  74,  16,  and  10 
respectively.  In  China  until  a  few  years  ago  erroneous  proportions  were  still  employed, 
namely,  61-5,  23,  and  15-5. 

The  chemical  reactions  occurring  during  the  explosion  of  black  powder  vary  according 
as  the  explosion  takes  place  under  pressure  or  at  the  ordinary  pressure  (deflagration). 
In  the  first  case,  Abel  and  Nobel  obtained,  from  1  gram,  of  ordinary  powder,  0-585  gram 
of  solid  products,  and  0415  gram  of  gas  (258  c.c. ),  according  to  the  following  equation : 
16KN03  +  21C  +  7S  =  13CO2  -f-  SCO  +  5K2C03  +  K2S04  +  2K2S3  +  16N;  in  addition 
there  are  formed  traces  of  potassium  thiocyanate  and  thiosulphate,  and  ammonium 
carbonate,  whilst  traces  of  sulphur  and  nitre  remain  unchanged,  as  the  proportions  taking 
part  in  the  above  reaction  are  77-7  nitre,  10-54  sulphur,  and  11-86  carbon.  With  1  gram 
of  powder  exploded  at  the  ordinary  pressure,  they  obtained  0-769  gram  of  the  same  solid 
products,  and  0-321  gram  of  gaseous  products  (about  193  c.c.),  thus  : 

16KN03  +  13C  +6S  =  11C02  +  21^003  +  5K2S04  +  K2S  +  16N; 

traces  of  other  products  are  also  formed,  since  this  equation  represents  82-4  per  cent,  nitre, 
9-5  sulphur,  and  8  carbon. 

Sporting  powder  should  burn  more  rapidly,  and  hence  contains  more  nitre  and  a  brown 
wood-charcoal  of  superior  quality.  In  different  countries  the  nitre  varies  from  75  to  78 
per  cent.,  the  carbon  from  12  to  15  per  cent.,  and  the  sulphur  from  9  to  12  per  cent.  Nowa- 
days, however,  most  sporting  powders  are  of  the  smokeless  type  with  a  nitrocellulose  basis.1 
With  mining  powders  the  production  of  a  large  quantity  of  gas  is  required,  so  that  the 
amounts  of  sulphur  (13  to  18  per  cent.)  and  of  carbon  (14  to  21  per  cent.)  are  increased, 
the  nitre  being  consequently  diminished  (60  to  72  per  cent. ) ;  if,  however,  the  proportion 
of  nitre  is  made  too  small,  the  explosion  becomes  very  slow,  more  CO  is  produced,  and 
the  gases  are  partly  able  to  escape  through  the  fissures  produced  before  the  end  of  the 
explosion,  the  useful  effect  being  thus  diminished.  Hard  rocks  require  increased  rapidity 
of  explosion,  but  with  tufa  or  granite  (to  obtain  large  blocks)  greater  slowness  of  explosion 
is  necessary. 

In  many  countries,  especially  in  the  United  States,  large  quantities  of  black  mine 
powder  with  a  basis  of  sodium  nitrate  are  made  for  prompt  consumption.  Such  powders 
were  first  patented  in  1857  by  the  Frenchman  Du  Pont  de  Nemours  (now  proprietor  in 
America  of  the  largest  explosives  works  in  the  world ;  during  the  European  War  400  tons 
of  nitrocellulose  per  day,  besides  enormous  quantities  of  other  military  explosives,  such 
as  trinitrotoluene,  picric  acid,  powder  B,  cordite,  etc.,  were  made  at  this  factory);  in 
1910  this  firm  produced  45,000  tons  of  black  sodium  nitrate  powder  (74  per  cent,  nitrate, 
10  per  cent,  sulphur,  16  per  cent,  wood  charcoal),  which  is  marketed  in  zinc  cases  to  protect 
it  from  moisture.  It  is  a  more  progressive  powder  than  the  ordinary  one  containing 
potassium  nitrate. 

MANUFACTURE  OF  POWDER.  The  prime  materials  should  be  prepared  with 
great  care.  The  sulphur  should  contain  no  trace  of  sulphuric  acid,  so  that  stick  sulphur 
and  not  flowers  of  sulphur  is  used ;  if  necessary,  it  is  purified  by  distillation,  and  should 
yield  less  than  0-25  per  cent,  of  residue  on  combustion.  At  the  present  time,  use  is  also 
made  of  the  sulphur  recovered  from  soda  residues  (see  Vol.  I.,  pp.  206  and  596).  The 
potassium  nitrate  is  sometimes  replaced  by  sodium  nitrate,  but  the  latter  is  more  hygroscopic 
and  impure.  The  nitre  should  contain  less  than  1  part  of  chlorides  per  3000,  and  should 

1  Smokeless  sporting  powders  are  of  two  kinds  :  light,  with  granules  gelatinised  superficially,  / 
and  condensed,  which  have  completely  gelatinised  granules  and  are  prepared  like  ordinary  smoke- 
less powders  (see  later,  pp.  295,  296),  being  often  scrap  from  these  cut  to  various  sizes.  The 
former  or  light  powder  is  made  by  mixing  the  different  components  and  coarsely  granulating 
the  moistened  (with  water  or  solvent  or  liquid  ingredient)  mass  through  sieves;  these  granules 
are  rounded  by  subjecting  them  to  a  rotary  and  oscillatory  movement  on  circular  cloths  moved 
horizontally  by  eccentrics,  then  partially'drying  at  50°  to  60°  and  afterwards  treating  in  revolving 
drums.  The  grains  are  finally  gelatinised  superficially  by  spraying  with  a  solvent  (e.  g.,  acetone, 
which  gelatinises  nitrocellulose,  this  being  one  of  the  usual  components)  and  at  the  same  time 
keeping  it  in  motion  in  a  vessel  with  a  double  bottom,  through  the  jacket  of  which  water  at 
50°  to  60°  circulates.  The  powder  is  then  dried  completely  in  a  current  of  warm  air  (at  40° 
to  50°). 


268  ORGANIC    CHEMISTRY 

be  free  from  perchlorates.1  Both  English  nitre  from  India  and  German  conversion  nitre 
are  used,  after  suitable  purification. 

The  wood  charcoal  should  be  highly  porous  and  should  burn  easily  without  leaving  an 
appreciable  quantity  of  ash ;  2  in  different  countries,  different  kinds  of  wood  are  used : 
in  Spain,  flax  and  vine  stalks ;  in  Germany,  dogwood,  the  alder,  and  the  willow ;  in  France, 
the  poplar,  lime,  etc. ;  and  in  Italy,  hemp  stalks,  etc.  In  some  cases,  charcoal  from  sugar, 
dextrin,  maize,  cork,  etc.,  is  used.  Charcoal  obtained  at  temperatures  exceeding  430°  is 
of  no  use  for  gunpowder. 

PULVERISATION  AND  MIXING  OF  THE  INGREDIENTS.  In  early  times  the 
ingredients  were  ground  and  mixed  by  hand  in  mortars,  but  machine  mills  were  used  as 

1  For  many  years  the  superiority  of  English  powders  could  not  be  explained,  and  it  was 
attributed  to  the  use  of  Indian  nitre,  refined  in  England,  whilst  all  over  Europe,  conversion  nitre, 
prepared  in  Germany,  was  employed.     On  the  other  hand,  the  Germans  showed  that  their  nitre 
was  very  pure,  as  it  contained  only  0-5  per  cent,  of  chlorides,  and  they  regarded  the  preference 
for  English  powder  as  the  result  of  prejudice.     In  1894,  however,  the  elder  Hellich  showed  that 
the  conversion  nitre  contained  also  perchlorate  and  chlorate  which  were  not  shown  in  the  estima- 
tion of  the  chlorides.     Spontaneous  explosions  of  powder  in  Servia  in  1896  were  ascribed  by 
Panaotovic  to  the  use  of  nitre  containing  perchlorates.     In  1897,  Kelbotz  showed  that  the 
perchlorate  is  not  distributed  homogeneously  through  the  crystals  of  nitre,  but  that  some  of  the 
latter  contain  more  (and  are  more  explosive)  and  others  less ;  hence  the  superiority  and  uniformity 
of  powders  free  from  perchlorate  were  explained.     The  perchlorate  in  nitre  is  estimated  by 
Selckmann's  method  (1898)  by  fusing  5  grams  of  the  nitre  with  20  grams  of  pure  lead  in  scales; 
the  fusion  is  first  gentle  for  15  minutes  until  the  mass  becomes  pasty,  after  which  the  temperature 
is  raised  for  a  short  time.     The  mixture  of  potassium  nitrite,  lead  oxide,  and  chlorides  is  poured 
into  water  and  the  chlorides  estimated,  the  excess  over  the  amount  originally  present  being  due 
to  the  chlorides. 

2  Under  similar  conditions,  the  readiness  with  which  powder  burns  is  increased  by  increased 
combustibility  of  the  charcoal.     Hence  it  is  necessary  not  only  to  use  a  suitable  method  of  pre- 
paring the  charcoal,  but  also  to  make  careful  choice  of  the  wood  to  be  carbonised.     Light,  soft 
wood  is  preferred,  and  of  the  different  parts  of  the  plant  the  best  are  branches  at  least  three 
years  old  (5  to  8  cm.  in  diameter);  the  bark  is  rejected.     For  powders  to  be  used  in  guns,  hazel 
or  dogwood  (Rhamnus  frangula)  or  hemp  stalks  are  used,  whilst  for  cannon  and  mining  powders, 
preference  is  given  to  white  willow  (Salix  alba),  alder,  poplar,  etc.     Hemp-stalk  charcoal  burns 
the  best,  and  about  40  parts  of  it  are  obtained  from  100  of  the  stalks ;   hazel-wood  gives  only 
33  per  cent,  of  charcoal.     The  wood,  freed  from  bark  and  well  dried  in  the  air  for  two  or  three 
years,  still  contains  about  20  per  cent,  of  moisture.     When  heated  out  of  contact  with  the  air, 
it  evolves  combustible  gases,  but  the  greater  part  of  the  wood  blackens  without  burning  and  forms 
charcoal.     It  is  of  importance  to  determine  the  best  conditions  for  carbonisation.     When  the 
temperature  is  not  very  high  (280°  to  340°),  a  light,  reddish,  readily  combustible  charcoal  is 
obtained,  whilst  at  higher  temperatures  a  black,  denser  charcoal  is  obtained  which  burns  slowly 
and  badly,  although  it  is  a  better  conductor  of  heat  and  electricity. 

Rapid  carbonisation  gives  a  diminished  yield,  but  the  charcoal  is  lighter  and  more  friable. 
The  charcoal  is  ground  just  before  using,  as  in  the  powdered  state  it  is  much  more  hygroscopic 
and  may  also  inflame  spontaneously. 

Charcoal  prepared  at  270°  is  partially  soluble  in  caustic  soda  solution,  whilst  it  is  insoluble 
if  prepared  at  above  330°. 

Carbonisation  of  wood  in  heaps  or  pits  is  no  longer  employed,  since  the  resulting  charcoal  is 
impure  and  non-uniform,  owing  to  the  impossibility  of  regulating  the  temperature.  So  that  at 
the  present  time  powder  factories  always  resort  to  charring  by  distillation,  or  charring  in  fixed 
or  movable  cylinders,  as  proposed  by  the  English  bishop,  Landlofi,  at  the  end  of  the  eighteenth 
century.  The  distillation  may  be  carried  out  in  fixed  horizontal  cylinders  (two  to  each  furnace), 
1-5  metre  long  and  0-65  metre  in  diameter,  but  with  this  arrangement  discharging  is  difficult 
and  sometimes  the  heated  charcoal  ignites.  It  is  better  to  use  fixed  vertical  cylinders  with 
openings  at  the  bottom  for  emptying,  or  movable  vertical  cylinders,  which  can  be  rotated  from 
time  to  time  during  the  heating.  In  every  cylinder,  a  space  is  left  for  the  introduction  of  a  pyro- 
meter to  indicate  the  temperature  of  the  wood.  The  furnace  is  first  heated  gently,  and  after 
three  hours  yellowish  fumes,  composed  of  water,  acetic  acid,  methyl  alcohol,  etc.,  begin  to  distil. 
After  this,  the  distillation  continues  without  further  heating  of  the  cylinder.  The  gases  are  led 
by  pipes  under  the  hearth,  where  they  burn  at  first  with  a  bright  red  flame  and  towards  the 
end  of  the  distillation  with  a  bluish  red  flame.  When  the  distillation  is  finished,  the  cover  of 
the  cylinder  is  raised  and  the  charcoal  discharged  into  suitable  movable  drums,  which  are 
immediately  closed  to  exclude  the  air.  Into  the  cylinder,  while  still  hot,  another  charge  of 
wood  is  at  once  introduced.  Each  charring  lasts  at  least  ten  hours.  In  three  or  four  days  the 
charcoal  is  cold  and  is  then  removed  lump  by  lump  from  the  cooling  drums,  any  that  is  in- 
sufficiently burnt  being  rejected.  The  colour  of  the  charcoal  is  coffee-black,  the  fracture  being 
velvety  and  of  the  same  colour. 

An  improved  process  of  distilling  wood  by  means  of  superheated  steam,  proposed  by  Violette 
in  1847  and  improved  by  Gossart  in  1855,  was  abandoned  on  account  of  its  excessive  cost. 

In  1899,  H.  Guttler  in  Germany  suggested  the  replacement  of  the  superheated  steam  by  hot 
carbon  dioxide  in  order  to  obtain  a  rapid  charring ;  after  the  operation,  the  mass  may  be  quickly 
cooled  by  a  current  of  cold  carbon  dioxide. 


MANUFACTURE    OF    GUNPOWDER 


269 


early  as  1350.  In  the  seventeenth  century,  the  use  of  wooden  stamps  became  widespread, 
but  these  were  the  cause  of  many" explosions,  so  that  the  vertical  mills  again  came  into 
use,  the  powder  being  kept  moistened  with  water  during  grinding.  After  1754  ordinary 
roll  mills  were  used.  At  the  present  time  the  ingredients  are  powdered  separately,  then 
partial  mixtures  of  sulphur  and  charcoal,  and  charcoal  and  nitre,  are  made,  these  being 
finally  united  and  intimately  mixed.  The  finer  the  materials  are  powdered  the  better 
will  be  the  resulting  powder. 

The  charcoal  and  the  sulphur  may  be  powdered  in  the  Excelsior  mill  (see  p.  201,  Figs. 
164,  165),  the  product  then  being  sieved  and  the  coarse  particles  reground.  The  nitre 
is  received  from  the  refiner  in  the  form  of  flour  and  only  requires  sieving. 

The  binary  mixtures  are  prepared  by  placing  the  powdered  substances  in  special  iron 
drums  (Fig.  184),  1-1  to  1-2  metres  in  diameter,  and  0'6  to  1-2  metres  long.  On  the  inner 
periphery  of  the  drum  are  12  to  16  transverse  ribs,  3  to  4  cm.  thick.  Hard  phosphor- 
bronze  balls,  15  to  20  mm.  in  diameter,  are  introduced  with  the  two  substances  through 
the  aperture  a,  which  corresponds  with  the  hinged  cover  6,  fixed  on  the  cylindrical  wooden 
casing  surrounding  the  drum.  This  wooden  casing  is  connected  with  a  leather  or  cloth 


FIG.  184. 


FIG.  185. 


bag,  c,  by  which  the  mixture  is  finally  discharged  into  the  barrels,  d,  these  being  closed 
hermetically  so  as  to  prevent  contact  with  the  air,  which  might  cause  ignition  (see  Vol.  I., 
Pyrophoric  Substances). 

The  drum  is  rotated  about  15  to  20  times  per  minute  for  eight  to  ten  hours,  100  to  150 
kilos  of  the  bronze  balls  being  used  per  200  kilos  of  the  mixed  substances ;  the  balls  are 
given  a  bumping  motion  by  the  peripheral  ribs  and  so  increase  the  fineness  of  the  powder. 
When  the  aperture,  a,  furnished  with  a  coarse  net,  is  opened  at  the  end,  the  powder  is 
discharged  and  the  balls  retained  for  a  subsequent  operation  (see  also  the  figures  of  ball 
mills,  Vol.  I,  pp.  651,  652). 

The  ternary  mixture  is  prepared  by  mixing  either  binary  mixture  with  the  third  con- 
stituent or  the  two  binary  mixtures  (carbon  +  sulphur,  and  carbon  +  nitre)  in  the  required 
proportions  Ln  a  rotating  cylinder  provided  with  stirrers,  or,  better,  in  a  drum  similar  to 
that  just  described.  After  this  the  mass  is  moistened  with  water  and  mixed,  and  then 
introduced  into  a  stamp  mill  (like  that  shown  in  Vol.  I.,  p.  653),  where  it  is  kept  moistened 
(with  about  10  per  cent,  of  moisture)  without  caking.  The  stamps  make  30  to  60  blows 
per  minute,  and  their  action  is  continued  for  at  least  twelve  hours  for  cannon  powder,  eight 
hours  for  mining  powder,  and  twenty-four  hours  for  sporting  powder.  The  cakes  thus 
obtained  then  pass  to  the  granulating  machine. 

In  many  factories,  however,  the  use  of  stamps  has  been  abandoned,  these  being  replaced 
by  vertical  iron  runners  (Fig.  185)  about  1-6  metres  in  diameter  and  40  cm.  thick,  and  weigh- 


270 


ORGANIC    CHEMISTRY 


FIG.  186. 


ing  about  5000  kilos  each.  They  rotate  on  a  very  hard  iron  plate  2  metres  in  diameter. 
The  two  runners  are  placed  at  different  distances  from  the  central  shaft,  which  is  actuated 
by  bevel  wheels  above  (as  in  the  figure)  or  below;  suitable  scrapers  detach  the  powder 
sticking  to  the  runners,  and  others  bring  the  powder  from  the  edge  to  the  centre  and  so 
under  the  runners.  The  incorporation  is  continued  for  three  hours  in  the  case  of  military 
powder  and  for  five  hours  with  sporting  powder,  the  velocity  of  the  runners  being  10  to  12 
revolutions  per  minute  at  first  and  only  1  revolution  in  20  minutes  towards  the  end  of  the 
operation,  so  that  highly  compressed  cakes  may  be  obtained. 
About  every  hour  the  mass  is  moistened  with  1  to  1-5  litres 
of  water  for  a  charge  of  20  kilos,  the  amount  of  water  used 
depending  on  the  hygrometric  state  and  temperature  of  the 
air.  The  water  dissolves  the  nitre,  which  is  thus  distributed 
uniformly  and  in  a  finely  divided  state  throughout  the  whole 
mass. 

In  some  factories,  compression  of  the  moistened  ternary 
mixture  is  effected  by  means  of  hydraulic  presses  (Fig.  186) 
between  a  number  of  separate  layers  of  copper  or  ebonite,  a 
pressure  of  100  atmos.  being  applied  for  three-quarters  of  an 
hour.  This  procedure  yields  very  compact  cakes,  having  the 
density  1-7  to  1-8. 

It  was  formerly  the  custom  in  France,  and  is  still  in 
Germany,  to  use  roller-presses  (laminoirs)  (Fig.  187)  formed 
of  three  superposed  rolls ;  the  lowest  one,  C,  of  cast-iron,  is 
driven  directly  and  transmits  the  movement  to  the  middle 
one,  B,  which  is  coated  with  paper;  this  then  drives  the 
uppermost  one,  A,  of  chilled  cast-iron.  The  endless  band,  D, 
collects  the  mixture  falling  from  the  hopper,  E,  and  carries  it 
between  B  and  A,  between  which  a  pressure  of  15  to  25  tons 
can  easily  be  obtained  by  means  of  the  lever,  L,  and 
weights,  P.  A  knife  is  arranged  so  as  to  scrape  the  com- 
pressed powder  from  the  band. 

As  a  rule,  moist  compression  gives  a  more  uniform  and  also  a  denser  mass. 
After  compression  the  cakes  still  contain  5  to  8  per  cent,  of  moisture,  and  they  are 
allowed  to  stand  for  seven  to  eight  days  in  well- ventilated  magazines.     After  this,  those  from 
the  hydraulic  presses  or  roller-presses  are  first  partly  dried  (see  later)  and  then  granulated, 
whilst  those  from  the  stamps  or  incorporating  mills,  being  less  moist,  are  granulated  directly. 
GRANULATION.     This  operation  serves  the  purpose  of  preventing  the  separation  of 
the  constituents,  and  of  rendering  the 
powder  less  hygroscopic  and  less  com- 
pact  (but  not  less  dense),  since  the 
combustion  of  the  granules  is  more 
rapid  than  that  of  the  fine  compact 
powder;  also,  the  finer  the  granula- 
tion the  more  rapid  is  the  combustion 
and  the  greater  the  mechanical  effect. 
The  finest  grains  are  used  for  sporting 
powders,  then  come  those  for  military 
rifles,  the  coarsest  grains  being  for 
cannon.    If  sporting  powder  were  used 
for  military  rifles,  the  barrel  would 
wear    out   rapidly    and    might   even  FIG.  187. 

split. 

It  was  only  after  1445  that  powder  for  artillery  was  granulated,  it  being  found  that 
the  effect  was  greater  than  that  of  the  non-granulated  and  non-compressed  powder.  Com- 
pression with  stamps  or  rolls  came  into  general  use  in  France  after  1525,  the  compressed 
mass  being  then  broken  up  with  wooden  hammers  and  granulated ;  for  this  purpose,  the 
mass  was  spread  out  on  a  large  sieve  and  covered  with  a  heavy  disc  of  wood,  the  sieve  being 
then  rotated  and  oscillated  until  all  the  powder  passed  through  it  in  grains. 

Later  the  Leftvre  graining  machine  was  devised,  and  this  is  still  in  use  in  France  and 


GRANULATION    OF    POWDER 


271 


Germany ;  this  machine  grades  the  grains  into  different  sizes  and  also  eliminates  all  dust, 
powders  showing  more  regular  and  rapid  combustion  being  thus  obtained. 

This  machine  (Figs.  188  and  189)  is  analogous  to  the  plane-sifter  used  for  flour.  It 
consists  of  an  octagonal  board  with  sides,  a,  having  a  diameter  of  2-5  metres  and  suspended 
from  the  ceiling  by  8  ropes,  b.  This  receives  a  circular  motion  by  means  of  an  eccentric 
formed  of  a  vertical  shaft,  c,  with  an  elbow-joint.  This  shaft  is  rotated  at  the  rate  of  75 
revolutions  per  minute  by  the  cog-wheels,  B.  On  the  board  are  fixed  8  or  10  triple  sieves, 
S,  to  which  the  powder  to  be  granulated  is  supplied  by  leather  or  cloth  tubes,  e.  The 

powder  falls  on  to  the  first  wooden 
sieve,  A,  with  a  mesh  of  3  to  4  mm., 
'the  coarse  lumps  being  gradually 
broken  by  a  disc  of  wood,  c,  weighing 
700  grams.  The  grains  then  pass  on 
to  a  second  sieve,  B,  of  metal,  3  to 
4  cm.  below,  and  then,  to  the  lowest 


FIG.  188. 


FIG.  189. 


one,  C,  which  is  of  hair  and  retains  the  grains  of  the  required  size,  whilst  the  dust  falls  into 
D  and  thence  through  the  leather  pipe,  g,  into  the  barrel,  p ;  the  uniformly  grained  powder 
is  discharged  into  q  through  /. 

More  common  at  the  present  time  is  the  granulating  machine  with  fluted  rolls,  first 
suggested  in  1819  by  the  Englishman,  Colonel  Congreve,  and  subsequently  improved  in 
various  ways.  This  machine  (Fig.  190)  consists  of  several  pairs  of  bronze  rolls,  A,  B,  C, 
fluted  longitudinally  and  transversely.  The  lumps  of  powder  from  the  breaker,  D,  are 
raised  to  E  by  an  endless  band,  and  fall  on  to  the  first  rolls,  A,  furnished  with  small  pyra- 
midal teeth  projecting  10  mm., 
then  on  to  the  second  rolls,  B, 
with  finer  teeth  (3  mm.),  and 
finally  on  to  the  smooth  rolls,  C, 
which  give  the  powder  the  ap- 
pearance of  shining  scales.  This 
distance  between  the  rolls  is 
adjustable,  and  the  teeth  are  kept 
clean  by  means  of  a  brush.  The 
granulated  powder  falls  on  to  a 
series  of  superposed  sieves,  S, 
which  are  oscillated  at  the  rate 
of  150  vibrations  per  minute,  and 
so  grade  the  powder,  the  final  dust  FIG.  190. 

being  discharged  at  ra.     Blasting 

powder,  which  has  the  size  of  peas,  is  not  passed  through  the  smooth  rolls.  By  varying 
the  mesh  of  the  sieves,  grains  of  any  desired  magnitude  are  obtainable.  Congreve's 
granulating  machine  gives  a  yield  four  or  five  times  as  great  as  that  of  Lefevre  (for  the 
same  consumption  of  power)  and  also  forms  less  dust. 

DRYING.  The  granulated  powder  is  sometimes  dried  by  spreading  it  out  in  layers 
5  cm.  deep  on  cement  floors  exposed  to  the  air  and  sun  and  mixing  it  occasionally  with 
rakes ;  this  drying  is  continued  until  the  moisture  is  reduced  to  3  per  cent. 

The  dust  and  residues  from  all  the  operations  are  mixed  with  the  ternary  mixture  before 
compression. 

Artificial   drying,   which  is   independent  of   climatic   conditions,  is   however,   more 


272 


ORGANIC    CHEMISTRY 


commonly  used.  In  early  times  the  powder  was  placed  in  copper  pans  heated  directly 
over  the  fire,  but  this  led  to  many  explosions ;  later  it  was  spread  out  on  cloths  in  a  chamber 
heated  by  a  stove  in  the  centre,  but  this  also  was  dangerous  even  when  the  stove  was  out- 
side the  chamber.  Nowadays  drying  is  generally  effected  by  air  (used  for  the  first  time 
in  England  in  1780)  which  is  heated  by  a  network  of  steam-pipes  and  is  injected  into  a 
drying-room  containing  the  powder  spread  on  cloth  in  layers  5  to  15  cm.  deep,  mixing 
with  wooden  rakes  being  resorted  to  about  every  two  hours.  The  air  passes  through  the 
powder  and  is  carried  off  by  flues ;  the  drying  takes  8  to  10  hours.  The  fire  of  the  steam- 
boiler  is  at  least  100  metres  from  the  drying-room. 

Dry  powder  can  be  powdered  between  the  fingers,  giving  a  pale,  grey  powder,  but  if 
not  dry  it  is  dark  and  sticks  to  the  hands.  In  some  factories  the  air  used  is  previously 
dried  (and  is  employed  cold  if  the  nitre  present  tends  to  effloresce,  but  hot  in  other  cases) 
by  being  forced  with  a  fan,  A  (Fig.  191),  through  fused,  spongy  calcium  chloride  or  con- 
centrated sulphuric  acid  contained  in  a  leaden  vessel,  D.  Thence  it  passes  into  the  chest, 
E,  filled  with  -lumps  of  quicklime,  which  holds  back  any  acid  carried  over.  It  is  then 
heated  in  the  brickwork  chamber,  B,  by  a  number  of  pipes,  c,  supplied  with  steam  at  d; 
the  warm,  dry  air  then  proceeds  through  the  tube,  V,  to  the  drying-rooms. 

The  proposal  has  also  been  made  to  dry  powder  by  heating  it  in  a  vacuum,  but  such  a 
process  is  too  costly  and  its  efficiency  low.  Drying  need  not  be  complete,  since  the  powder 
has  still  to  be  glazed. 

GLAZING.  The  dried  grains  are  rough,  angular,  and  highly  porous.  In  order  to  give 
a  brighter  appearance  to  the  powder  and  to  render  it  more  uniform  and  dense  and  less 


si  V 


FIG.  191. 


FIG.  192. 


hygroscopic,  it  is  treated  in  wooden  glazing  drums  (Champy  drums,  similar  to  those  used 
for  the  binary  mixtures ;  see  above)  after  having  been  passed  through  a  fine  sieve  to  free  it 
from  adherent  dust.  The  inner  walls  of  the  drum  are  first  moistened  and  the  drum  slowly 
rotated  while  the  powder  is  being  introduced  until  about  300  kilos  are  present,  the  Velocity 
being  then  raised  to  12  to  14  revolutions  per  minute ;  the  finer  the  granulation  the  more 
rapid  must  be  the  rotation.  In  this  way  the  powder  becomes  heated  to  about  50°  and 
assumes  a  gloss ;  care  must,  however,  be  taken  that  it  does  not  become  too  hot,  and  towards 
the  end  of  the  glazing  the  rotation  must  be  slackened.  A  little  graphite  is  sometimes 
added  (0-25  per  cent.)  to  render  the  powder  less  hygroscopic  and  more  glossy  and  to  facili- 
tate the  rounding  process.  Glazing  takes  four  to  five  hours  for  blasting  powders  and  fifteen 
to  twenty  hours  for  sporting  powder. 

Glazing  is  due  to  the  rubbing  of  the  grains  one  against  the  other.  The  powder  is 
subsequently  dried  completely  in  the  usual  drying-rooms,  or  the  panels  of  the  drum  may 
be  opened  so  as  to  allow  of  the  escape  of  the  warm,  moist  air. 

Polishing  and  sorting  are  carried  out,  after  the  glazing  and  drying,  to  remove  the  last 
traces  of  dust  and  separate  the  different  sizes  of  grains.  For  these  purposes  a  battery  of 
sieves  similar  to  those  of  the  Lefevre  and  Congreve  graining  machines  is  used,  the  sieving 
being  repeated  several  times.  The  dust  contains  about  75  per  cent,  of  carbon. 

PRISMATIC  POWDER  FOR  CANNON.  It  was  shown  by  San  Roberto  as  early  as 
1852  that  cannon  give  better  results  if  charged  with  compressed  cartridges  of  regular  form, 
and  the  American,  General  Rodman,  proposed  in  1860  to  make  large  grains  of  regular 
shape.  The  use  of  such  powder  was  extended  in  Russia  by  General  Doremus,  and  also 
in  other  countries,  but  was  found  to  give  better  results  for  blasting  than  for  military  powder. 
In  England,  Armstrong's  grains,  in  the  form  of  hazel-nuts,  met  with  great  success  and  are 
still  used.  In  1879,  by  means  of  special  hydraulic  presses  (cam-presses),  Wischnegradsky 
prepared  the  first  prismatic  powders,  six  or  seven  holes  being  left  in  each  prism  (Fig.  192) 


NITROGLYCERINES  273 

to  diminish  the  initial  pressure  on  the  cannon  and  give  a  more  regular  combustion.  Every 
prism  is  25  mm.  high  and  40  mm.  in  diameter,  and  weighs  40  grams ;  it  has  the  density 
1-66  and  bears  the  mark  C.66.  It  is  used  for  15  to  26  mm.  guns,  whilst  that  for  larger 
cannon  has  the  same  volume  but  the  sp.  gr.  1-75  (marked  C.75).  The  brown  prismatic 
powder  of  Rottweil  of  Hamburg  has  the  sp.  gr.  1-86  (C.86),  and  is  used  for  large  cannon, 
since  it  burns  slowly,  gives  little  smoke,  keeps  well  and  imparts  to  the  projectile  a  high 
initial  velocity,  which  increases  until  the  mouth  of  the  cannon  is  reached ;  it  is  prepared 
with  rye-straw  charcoal  and  contains  78  per  cent,  of  nitre,  3  per  cent,  of  sulphur,  and  19 
per  cent,  of  brown  charcoal.  The  Italian  chocolate  powder  contains  79  per  cent,  of  potassium 
nitrate,  18  per  cent,  of  carbon,  and  3  per  cent,  of  sulphur. 

PACKING.  Powder  is  packed  in  bags  containing  from  50  kilos,  these  being  placed  in 
barrels  or  cases  coated  inside  with  paper  and  outside  with  cloth.  Each  case  bears  a  label 
of  a  colour  indicating  the  nature  of  the  powder  (rifle,  cannon,  etc.).  Sporting  powder  is 
placed  in  tin  boxes  holding  100,  200,  500,  1000,  or  2000  grams,  these  being  then  arranged 
in  cases  containing  25  kilos. 

Powder  for  firing  volleys  or  ball  is  converted  directly  into  cartridges,  which  are  then 
stored  in  cases  in  sawdust,  cotton  waste,  or  similar  packing. 

CHARACTERS  AND  PROPERTIES  OF  BLACK  POWDER.  It  has  a 
slate-grey  colour,  and,  if  too  black,  either  it  is  damp  or  it  contains  too  much 
charcoal.  Certain  military  powders  have  a  brown  colour,  as  they  are  prepared 
with  reddish-brown  charcoal.  If  rubbed  on  a  sheet  of  paper  it  should  not  leave 
a  dirty  mark,  as,  if  it  does,  it  contains  dust  or  moisture.  When  a  small  heap  of 
powder  is  ignited  on  a  sheet  of  white  paper  it  should  burn  rapidly  without 
leaving  a  residue  or  burning  the  paper;  if  very  black  spots  remain,  there  is 
excess  of  charcoal,  or  if  yellow  ones,  excess  of  sulphur.  On  exposure  to  the 
air,  good  powder  absorbs  only  1'5  to  2  per  cent,  of  moisture,  whilst  as  much  as 
14  per  cent,  may  be  absorbed  by  inferior  powder.  If  the  moisture-content  of 
powder  is  only  5  per  cent,  it  may  be  removed  without  damage  to  the  powder, 
but  nioister  powders  cannot  be  restored  to  their  original  strength  by  drying, 
since  the  grains  become  covered  with  a  crust  of  nitre.  The  finer  the  powder 
and  the  richer  in  charcoal,  the  more  hygroscopic  it  is. 

The  temperatures  of  ignition  and  explosion  are  the  same,  and  ignition  or 
explosion  can  be  produced  by  red-hot  iron  or  any  ignited  substance,  or  with 
less  ease  by  percussion,  shock,  or  discharge.  It  is  more  difficult  to  ignite  by 
a  blow  of  iron  on  copper,  or  copper  on  copper,  than  by  one  of  iron  on  iron  or 
brass,  or  of  brass  on  brass,  etc.  Powder  ignites  more  readily  by  a  spark  or 
red-hot  body  than  by  a  gas-flame.  Guncotton  burns  on  powder  without 
igniting  it.  Different  powders  ignite  between  270°  and  320°  according  to  the 
form  of  the  granulation. 

NITROGLYCERINES   AND    DYNAMITES 

The  name  nitroglycerine  is  given  improperly  to  nitric  esters  of  glycerine,  since  they  do 
not  contain  true  nitro-groups  (N02)  united  directly  with  carbon,' as  is  often  the  case  in 
benzene  derivatives.  On  the  contrary,  the  union  is  effected  through  an  intermediate 
oxygen  atom,  so  that  these  compounds  should  rather  be  called  glyceryl  nitrates. 

Being  a  trihydric  alcohol,  glycerine  can  form  three  such  compounds,  the  only  one  known 
until  quite  recently  being  trinitroglycerine,  containing  18-5  per  cent,  of  nitrogen  and  having 
very  considerable  industrial  importance. 

In  1903,  Mikolajczak  prepared  also  pure  DINITROGLYCERINE,  C3H5-  OH(ON02)2, 
containing  15-4  per  cent,  of  nitrogen,  and  he  proposed  to  use  it  as  an  explosive,  as  it 
possesses  almost  all  the  ballistic  advantages  of  trinitroglycerine  and  is  not  easily  frozen ; 
it  is,  however,  very  hygroscopic  and  readily  soluble  in  water  and  in  acids.  In  1904  he 
proposed  to  add  it  to  trinitroglycerine  to  render  the  latter  more  highly  resistant  to  frost, 
and  since  then  it  has  been  manufactured  on  an  industrial  scale  at  Costrop  (Gel-many). 
As  early  as  1890  Wohl  (Ger.  Pat.  58,957)  had  already  described  various  properties  of  monc- 
and  di-nitroglycerines,  including  the  power  of  lowering  the  freezing-point  of  trinitroglycerine. 
VOL.  n.  18 


274  ORGANIC    CHEMISTRY 

In  1906  Will  showed  that  sometimes  the  dinitro-compound  raises,  instead  of  lowering,  the 
solidifying  point  of  trinitroglycerine. 

Dinitroglycerine  is  prepared  by  nitrating  100  parts  of  glycerine  with  400  parts  of  nitric- 
sulphuric  mixture  containing  8  to  12  per  cent.  H2O,  60  to  70  per  cent.  H2SO4,  and  15  to 
32  per  cent.  HN03;  at  the  end  of  the  reaction,  the  mass  is  poured  into  an  equal  volume 
of  water,  and  the  acid  neutralised  with  calcium  carbonate,  when  the  dinitroglycerine 
separates  as  a  dense,  floating  oil.  During  the  reaction,  the  temperature  is  maintained  at 
18°  to  20°  by  cooling  with  ice.  Dinitroglycerine  is  also  formed  on  dissolving  trinitro- 
glycerine in  sulphuric  acid  and  then  diluting  the  solution  with  a  little  water.  In  whatever 
way  it  is  prepared  (e.g.,  by  treating  1  part  of  glycerine  with  2  parts  of  sulphuric  acid, 
separating  by  means  of  lime  the  glycerinedisulphuric  acid  formed  and  treating  this  with 
nitric  acid,  as  proposed  by  Escales  and  Novak,  1906),  a  mixture  of  the  two  possible  iso- 
merides  is  always  obtained:  dinitroglycerine  K  (i.e.,  ay-),  N03-CH2-CH(OH)-CH2-NO3, 
and  dinitroglycerine  F  (i.  e.,  a  /?-),  NO3-CH2'CH(N03)-CH2-OH,  which  was  studied  by 
W.  Will  (1908).  The  mixture  forms  an  almost  colourless  or  faintly  yellow  oil,  sp.  gr. 
1-47  at  15°,  which  freezes  at  below  — 30°  to  a  glassy  mass,  this  distilling  almost  undecom- 
posed  at  146°  under  reduced  pressure  (15  mm.) ;  at  15°  it  is  soluble  to  the  extent  of  8  per 
cent,  in  water  and  at  50°  to  the  extent  of  10  per  cent.  In  dilute  sulphuric  or  nitric  acid 
it  dissolves  in  all  proportions  and  by  sulphuric  acid  (up  to  70  per  cent. )  it  is  transformed 
into  mononitroglycerine  and  then  into  glycerine.  It  is  very  hygroscopic  and,  when  dry, 
dissolves  or  gelatinises  nitrocellulose  (guncotton  or  collodion-cotton)  very  well.  The  two 
isomerides  may  be  separated  by  taking  advantage  of  the  fact  that,  in  the  air,  the  F  com- 
pound absorbs  3  per  cent,  of  water  and  is  transformed  into  a  crystalline  hydrate, 
3(C3H6O7N2)  +  H20,  whilst  the  other  remains  liquid.  The  .F-form  gives  a  nitrobenzoyl- 
derivative  melting  at  81°,  the  corresponding  compound  of  the  ./f-isomeride  melting  at  94°. 
In  the  dry  state,  the  dinitroglycerines  are  as  useful  for  explosives  as  the  trinitro-compound, 
but  when  moist  they  are  much  inferior.  A  mixture  of  50  per  cent,  dinitro-  and  50  per  cent, 
trinitro -glycerine  freezes  below  —20°. 

Of  MONONITROGLYCERINE,  C3H5(OH)2  •  N03,  the  pure  a-  and  /3-isomerides  are 
known  (W.  Will,  1908).  These  are  not  true  explosives  and  dissolve  to  the  extent  of  70  per 
cent,  in  water.  The  a-compound  melts  at  58°  and  boils  at  155°  to  160°  under  15  mm. 
pressure. 

Nitrochlorhydrin,  C3H5C1(N03)2,  and  Tetranitrodiglycerine  (see  p.  218)  have  also 
been  proposed  as  non-congealing  explosives,  but  better  still  for  this  purpose  are  the 
nitroacetins  (V.  Vender)  (see  later).1 

1  Dinitromonochlorhydrin  is  obtained,  according  to  F.  Roewer  (1906),  by  nitrating  the 
monochlorhydrin  in  the  same  manner  as  glycerine  is  nitrated  (see  later),  and  is  then  quickly 
separated  from  the  top  of  the  nitric-sulphuric  acid  mixture  as  an  oil  which  is  easily  rendered 
stable  by  washing  with  water  and  soda.  It  forms  a  faintly  yellow,  mobile  oil  of  aromatic  odour, 
sp.  gr.  1-541  at  15°,  soluble  in  alcohol,  ether,  acetone,  or  chloroform,  but  insoluble  in  water  and 
in  acids.  At  180°  it  gives  yellow  vapours,  and  at  190°  boils  without  detonation  or  deflagration, 
and  with  only  slight  decomposition;  under  a  pressure  of  15  mm.  it  distils  unchanged  at  121°  to 
123°  as  an  almost  colourless  oil.  It  is  much  more  stable  towards  pressure  than  nitroglycerine, 
although  possessing  almost  the  same  explosive  properties.  It  does  not  freeze  even  at  —  30° 
and  is  not  hygroscopic.  It  dissolves  nitrocellulose,  forming  explosive  gelatine,  and  mixes  readily 
with  nitroglycerine,  giving  non-congealing  dynamites  (with  5  to  20  per  cent,  of  nitrochlorhydrin, 
Ger.  Pat.  183,400),  these  being  prepared  by  nitrating  directly  a  mixture  of  glycerine  and 
chlorhydrin.  In  order  to  avoid  the  inconvenient  effects  on  miners  of  the  hydrochloric  acid 
formed  in  the  explosion  of  nitrochlorhydrin,  potassium  nitrate  is  added ;  during  the  explosion 
this  is  transformed  into  potassium  carbonate,  which  neutralises  the  acid. 

Dinitroacetylglycerine,  C3H6(ONO2)2(OCOCH3),  is  obtained  by  nitrating  the  monoacetinin 
the  same  apparatus  as  is  used  for  nitroglycerine,  but  using  an  acid  mixture  containing  a  pre- 
ponderance of  nitric  acid,  e.  g.,  65  per  cent.  HN03  and  35  per  cent.  H2S04.  The  dinitroacetyl- 
glycerine,  being  somewhat  soluble  in  water,  is  lost  to  some  extent  during  the  washing.  It  is 
a  yellowish  oil,  sp.  gr.  1-45  at  15°,  and  is  soluble  in  alcohol,  acetone,  ether,  nitroglycerine,  or 
nitric  acid,  and  almost  or  quite  insoluble  in  water,  benzene,  or  carbon  disulphide.  It  contains 
12-5  per  cent,  of  nitrogen  and  with  double  its  weight  of  nitroglycerine  gives  a  mixture  with 
16-5  per  cent,  of  nitrogen,  which  has  a  lower  freezing-point  (below  —  20°)  than  any  other  mixture 
of  these  substances.  It  serves  well  for  preparing  non-congealing  dynamites,  and  as  it  dissolves 
nitrocellulose  easily  it  may  be  used  for  gelatinising  smokeless  powders. 

Dinitroformylglycerine,  C3H8(ONO2)2(O  •  CHO ),  is  prepared  in  a  similar  manner  to  the  pre- 
ceding compound,  or,  together  with  nitroglycerine,  by  nitrating  the  product  obtained  by  heating 
two  parts  of  glycerine  with  one  part  of  oxalic  acid  for  twenty  hours  at  140°.     Nitroformin  and  ' 
nitroacetin  have  explosive  powers  rather  inferior  to  that  of  nitroglycerine. 


TRINITROGLYCERINE  275 

CH20  •  N02 

TRINITROGLYCERINE,    CHO  •  N02  or  C3H6(0  •  N02)3. 
CH20-N02 

This  was  discovered  in  February  1847  by  Ascanio  Sobrero,1  who  called  it  Pyroglycerine 
and  established  its  explosive  properties  but  regarded  its  industrial  manufacture  as  too 
dangerous.  Its  chemical  composition  was  determined  by  Williamson  in  1854.  At  first 
it  was  used  only  in  small  doses  as  a  medicine,  owing  to  its  marked  power  of  inducing  dilata- 
tion of  the  blood  vessels,  and  afterwards  its  1  per  cent,  alcoholic  solution  was  administered 
in  1  gram  doses  under  the  name  glonoin,  especially  by  American  doctors,  in  cases  of  cardiac 
neuralgia,  nervous  disorders,  hemicrania,  hiccough  and  sea-sickness.  Later,  after  various 
unavailing  attempts,  Alfred  Nobel  succeeded  in  applying  it  industrially,  and  in  1863 
established  two  nitroglycerine  factories,  one  at  Stockholm  and  the  other  at  Lauenburg, 
near  Hamburg;  the  former  blew  up  in  1864,  while  the  ship  "European,"  carrying  nitro- 
glycerine, blew  up  in  Colon  harbour,  and  other  explosions  occurred  in  England,  at  Sydney, 
at  San  Francisco,  etc.  In  spite  of  the  large  consumption  of  nitroglycerine  in  many  countries, 
these  accidents  were  followed  by  the  almost  universal  prohibition  of  its  manufacture. 
Fortunately  just  at  this  time  Nobel  discovered  a  very  happy  solution  of  the  problem  which 
completely  eliminated  this  danger,  by  mixing  the  nitroglycerine  with  inert  substances 
(kieselguhr  or  infusorial  earth)  and  thus  obtaining  dynamite,  this  being  to-day  at  the  head 
of  the  great  explosives  industry. 

PROPERTIES.  When  pure  it  is  a  dense,  almost  colourless  or  faintly 
yellow  liquid  of  sp.  gr.  1'6  at  15°,  T604  at  11°,  1-588  at  25°,  and  when  it  freezes 
its  density  increases  by  almost  one-tenth.  It  is  odourless  and  has  a  sweetish, 
burning  taste.  It  is  almost  insoluble  in  water  (0'16  to  0'20  per  cent,  being 
dissolved  at  15°),  is  not  hygroscopic,  and  dissolves  easily  in  concentrated 
alcohol,  ether,  benzene,  chloroform,  glacial  acetic  acid,  toluene,  nitrobenzene, 
phenol,  acetone,  olive  oil,  and  concentrated  sulphuric  acid  (sp.  gr.  T845), 
and  to  a  less  extent  in  nitric  acid  and  still  less  in  hydrochloric  acid;  it  is, 
however,  insoluble  in  carbon  disulphide,  glycerine,  petroleum,  vaseline,  tur- 
pentine, benzine,  carbon  tetrachloride,  and  the  nitric-sulphuric  acid  mixture 
used  in  its  manufacture.  In  solution  it  will  not  explode.  It  evaporates 
spontaneously  and  in  very  small  quantities  even  at  50°,  and  if  gradually  heated 
to  109°  it  begins  to  decompose  with  evolution  of  brown  nitrous  vapours. 
_  Its  specific  heat  is  0'356,  and  its  heat  of  solidification  23  to  24  Cals. 

At  a  red  heat  it  evaporates  without  decomposing,  but  if  it  begins  to  boil 
vigorously  during  the  heating,  there  is  danger  of  explosion.  According  to 
Champion,  pure  nitroglycerine  in  small  quantities  boils,  giving  yellow  vapours, 
at  185°,  evaporates  slowly  at  194°  and  rapidly  at  200°,  burns  quickly  at  218° 
and  detonates  with  difficulty  at  241°,  violently  at  257°,  feebly  at  267°,  and 
feebly  with  flame  at  287°  (being  in  the  spheroidal  state). 

When  heated  in  small  quantities  in  thd  bunsen  flame,  it  burns  without 
exploding,  and  if  spread  in  a  thin  layer  on  paper  it  ignites  with  difficulty  and 
burns  only  partially.  Explosion  of  nitroglycerine  can  be  induced  either  by 
violent  percussion  at  a  temperature  of  250°,  or  by  energetic  detonation  (e.  g., 
by  explosion  of  fulminate  of  mercury). 

Nitroglycerine  may  be  easily  supercooled  below  its  solidifying  point.  Kast 
(1905)  showed  that  nitroglycerine  represents  a  case  of  monotropic  allotropy 

1  Ascanio  Sobrero  was  born  at  Casalmonferrato  on  October  12,  1812.  He  studied  first 
medicine  and  then  chemistry.  In  1840  he  went  to  complete  his  chemical  studies  in  the  laboratory 
of  the  celebrated  Pelouze  at  Paris,  where  he  stayed  two  years,  and  in  1843  he  worked  in  Liebig's 
laboratory  at  Giessen.  In  1845  he  became  Professor  of  Applied  Chemistry  at  Turin,  where  he 
taught  until  1883.  He  died  on  May  26,  1888,  after  a  modest  life,  during  which  he  filled  various 
honorary  social  positions.  It  was  always  his  aim  that  science  should  not  be  made  a  pretext 
or  means  of  dishonourable  undertakings  or  of  business  speculations. 


276  ORGANIC    CHEMISTRY 

(see  also  Vol.  I.,  p.  208),  i.  e.,  it  has  two  freezing-points,  +  2'1°  and  -}-  13'50, 
corresponding  with  different  crystalline  forms.1 

The  heat  of  transformation  of  1  gram  of  liquid  nitroglycerine  into  the  solid 
labile  form  is  5*2  cals.,  and  that  of  the  latter  into  the  solid  stable  isomeride 
28  cals.,  this  being  obtained  by  seeding  with  a  crystal  of  the  stable  form  and 
stirring  at  0°  (Hibbert  and  Fuller,  1913). 

When  frozen,  nitroglycerine  explodes  with  more  difficulty  than  in  the 
liquid  form.  Pure  nitroglycerine  will  not  redden  blue  litmus  paper  or  turn 
starch  paste  and  potassium  iodide  blue,  unless  it  contains  free  acids  or  nitrous 
compounds  due  to  partial  decomposition. 

Impure  nitroglycerine  readily  decomposes  and  may  explode  spontaneously,  whilst 
in  the  pure  state  it  keeps  indefinitely.  A  sample  of  nitroglycerine  (200  grams)  prepared 
by  Sobrero  in  1847  is  still  kept  under  water  in  the  Nobel  factory  at  Avigliana. 

When  decomposing,  nitroglycerine  turns  green,  owing  to  the  formation  of  N2O  and 
N2O3 ;  CO2,  CO,  H2O,  N,  and  O  (see  also  p.  259)  are  also  successively  formed.  In  exploding, 
1  litre  of  nitroglycerine  produces  1298  litres  of  gas,  which,  at  the  temperature  of  explosion, 
occupies  a  space  of  10,400  litres. 

In  large  doses  nitroglycerine  is  poisonous  and  its  vapour  causes  headache  (especially 
at  the  back  of  the  head),  giddiness,  and  vomiting.  These  effects  are  produced  even  by 
working  with  or  simply  touching  nitroglycerine,  and  are  cured  by  means  of  cold  compresses 
on  the  head,  by  breathing  fresh,  pure  air,  and  by  drinking  coffee  and  taking  suitable  doses 
of  morphine  acetate. 

Workmen  who  handle  the  nitroglycerine  paste  during  the  manufacture  of  the  various 
dynamites  become  habituated  to  it  in  two  or  three  days  and  afterwards  feel  no  ill  effects. 
Nitroglycerine  is  moderately  easily  decomposed  by  alcoholic  potassium  hydroxide  (with 
separation  of  glycerine),  and,  when  necessary,  this  reaction  is  employed  to  destroy  and 
render  harmless  small  quantities  of  nitroglycerine;  similarly  benches  or  floors  on  which 
nitroglycerine  is  spilt  are  washed  with  caustic  alkali  solutions  : 

C3H5(ON02)3  +  5KOH  =  KN03  +  2KN02  +  CH3  •  COOK  +  H  •  COOK  +  3H20 ; 

a  little  ammonia  is  also  formed.     With  reducing  agents  it  gives  ammonia  and  glycerine, 
whilst  with  concentrated  sulphuric  acid  it  yields  nitric  acid  and  glycerinesulphuric  acid.2 

1  Both  nitroglycerine  and  also  dynamites  and  smokeless  powders  prepared  from  it  are  liable 
to  sob'dify,  and  although  they  are  then  more  stable  (or  as  stable  as  the  liquid,  as  was  shown  by 
Hess,  Dupre,  Cronquist,  Will,  etc.)  the  thawing  is  accompanied  by  danger,  and  when  not  carried 
out  with  great  precautions  has  often  led  to  fatal  explosions,  these  being  sometimes  caused  by  the 
mere  rubbing  of  the  crystals.     Indications  will  be  given  later  of  the  precautions  taken  in  magazines 
to  prevent  freezing,  and  mention  may  be  made  here  of  the  attempts  which  have  been  made  to 
render  nitroglycerine  non-congealable.     As  early  as  1895  it  was  proposed  to  add  nitrobenzene*  to 
nitroglycerine  to  lower  the  freezing-point,  and  later  the  use  of  orthonitrotoluene  was  suggested, 
but  the  practical  results  were  not  very  satisfactory  in  either  case,  the  depression  of  the  freezing- 
point  being  very  small.     Substances  were  required  which  were  almost  as  explosive  as  trinitro- 
glycerine,  and  were  insoluble  in  water  and  stable  on  heating,  and,  in  addition,  were  good  solvents 
for  nitrocelluloses  (for  making  smokeless  powders).    These  conditions  were  well  satisfied  by  the 
nitroformins  and  nitroacetins  tested  by  Nobel  as  early  as  1875.  but  rendered  practically  useful  in 
1906  by  V.  Vender.    The  best  results  are  given  by  dinitromonoacetin,  which  is  obtained  from  the 
monoacetin  of  glycerine  prepared  by  the,  ordinary  method  used  for  esterifying  alcohols  with 
acids  (see  later:  Esters).     Forty  parts  of  the  monoacetin  are  introduced  slowly  into  a  mixture 
of  100  parts  of  nitric  acid  (sp.  gr.  1-530)  and  25  parts  of  oleum  or  Nordhausen  sulphuric  acid 
(containing  25  per  cent,  of  free  S03),  the  mass  being  cooled  so  that  the  temperature  does  not 
exceed  25°.     The  whole  is  then  poured  into  water  and  washed  with  cold  and  afterwards  with 
hot  (70°)  dilute  soda.     By  this  means  an  oil  is  obtained  having  sp.  gr.  1-45  and  containing  12-5 
per  cent,  of  nitrogen ;   it  is  insoluble  in  water,  carbon  disulphide  or  benzine,  but  dissolves  un- 
changed in  nitric  acid,  nitroglycerine,  methyl  or  ethyl  alcohol,  acetone,  acetins,  etc.     Even  in  the 
cold,  it  has  considerable  solvent  and  gelatinising  power  for  collodion-cotton  and  guncotton 
(with  13-4  per  cent,  of  nitrogen )  and  the  resulting  explosive  gelatines  do  not  freeze  even  at  —  20°. 
Naukhoff  (1908)  has  proposed  the  addition  of  nitromethane  or  nitroethane  to  dynamite  to  lower 
its  freezing-point;   mono-  and  di-nitroglycerines  also  give  good  results  (see  pp.  273,  274).     In 
1866,  Rudberg  patented  in  Sweden  the  addition  of  nitrobenzene  to  obtain  non-congealing 
dynamites,     fii  the  Arendonck  factory   (Belgium)  Leroux  in    1903  successfully   used  liquid 
dinitrotoluene  to  render  dynamite  incongealable ;   Mikolajczak  in  1904  utilised  dlnitroglycerine 
for  the  same  purpose.     The  number  of  accidents  has  been  reduced  to  one-half  in  this  way. 

2  In  certain  practical  cases  the  following  reactions  may  be  of  interest :  Nitroglycerine  is  not 
altered  by  prolonged  contact  with  nitrates  of  Ca,  Co,  Na,  Ba  and  K,  with  chlorides  of  Ca,  Ba 


MANUFACTURE  OF  NITROGLYCERINE  277 

Characteristic  Reactions.  According  to  Weber,  small  quantities  of  nitroglycerine  are 
detected  by  treatment  with  aniline  and  concentrated  sulphuric  acid ;  a  reddish- purple 
coloration  is  obtained  which  turns  green  on  addition  of  water.  To  establish  the  purity 
and  keeping  qualities  of  nitroglycerine,  the  nitrogen  is  determined  and  Abel's  heat  test 
carried  out  (see  later,  Testing  of  Explosives);  if  it  is  satisfactory,  2  c.c.  of  it  withstands 
15  to  25  minutes'  heating  at  82°  without  giving  sufficient  nitrous  vapours  to  be  detectable 
by  means  of  starch  and  potassium  iodide  paper. 

This  reaction  is,  however,  given  by  nitroglycerine  kept  for  a  few  days  at  a  temperature 
exceeding  45°,  or  for  a  long  time  below  this  temperature. 

PREPARATION.  It  is  obtained  by  the  action  of  a  mixture  of  nitric  and 
sulphuric  acids  on  glycerine  : 

C3H5(OH)3  +  3HN03  =  3H20  +  C3H5(N03)3. 

The  mono-  and  dinitro-compounds  are  probably  formed  as  intermediate 
products  of  this  reaction. 

The  presence  of  sulphuric  acid,  which  plays  no  apparent  part  in  the  change, 
is  usually  regarded  as  being  necessary  to  maintain  the  nitric  acid  at  a  high 
concentration,  i.  e.,  to  decompose  the  hydrates  formed  by  nitric  acid  with  the 
water  from  the  reaction  (HNO3,  H20 — HN03,  3H2O)  and  so  regenerate  mono- 
hydrated  nitric  acid,  which  acts  on  the  glycerine  (Kullgren,  1908).  If  the 
function  of  the  sulphuric  acid  were  merely  to  fix  the  water,  phosphoric  acid 
could  be  used  in  its  place,  but  if  this  is  done  no  nitroglycerine  is  obtained 
(see  succeeding  Note). 

The  excess  of  the  nitric-sulphuric  mixture  which  is  always  used  helps  to 
produce  a  moderately  complete  separation  of  the  nitroglycerine,  which  has  a 
slightly  lower  density,  so  that  it  is  possible  to  recover  the  acids  employed. 
Although  nitroglycerine  is  soluble  in  sulphuric  or  nitric  acid  alone,  it  does  not 
dissolve  in  the  mixed  acids,  but  if  one  of  the  two  acids  is  in  large  excess,  a  con- 
siderable amount  of  nitroglycerine  remains  in  solution  and  is  lost.  In  the 
nitration,  the  whole  of  the  glycerine  cannot  be  added  at  one  time,  since  sufficient 
heat  would  in  that  way  be  developed  to  produce  decomposition  and  explosion 
of  the  nitroglycerine  instantaneously  formed.  It  is  also  not  convenient  to 
reverse  the  operation,  that  is,  to  add  the  mixed  acids  gradually  to  the  glycerine, 
the  greater  density  of  the  latter  rendering  rapid  and  homogeneous  mixing 
difficult :  it  is  hence  preferable  to  run  the  glycerine  slowly  into  the  acid  mixture 
and  to  keep  the  latter  continually  and  thoroughly  stirred  and  cooled. 

MANUFACTURE.  The  theoretical  proportions  of  the  reacting  substances  *  would  be 
100  parts  by  weight  of  glycerine  and  205-43  of  pure  nitric  acid,  the  theoretical  yield  of 
trinitroglycerine  being  then  246-74  parts.  On  a  large  scale,  however,  the  whole  of  the 
nitric  acid  does  not  come  into  immediate  contact  with  the  whole  of  the  glycerine,  and  it 
is  hence  better  to  use  a  slight  excess  of  nitric  acid  (240  parts  or  even  more);  the  amount 

and  Fe,  with  sulphates  of  K,  Na  and  Ca,  or  with  calcium  carbonate.  With  silver  nitrate  it  gives 
a  black  precipitate  of  silver  oxide,  while  with  stannous  chloride  it  precipitates  tin  peroxide  and 
forms  a  mirror  at  the  surface.  It  reduces  potassium  dichromate  partly  to  chromate,  and  gives 
a  slight  precipitate  of  copper  oxide  with  copper  sulphate  and  a  voluminous  precipitate  and 
nitrous  vapours  with  ferrous  sulphate.  Sulphides,  including  hydrogen  sulphide,  decompose 
nitroglycerine  slowly  with  separation  of  sulphur  and  glycerine. 

1  The  prime  materials  used  in  the  manufacture  of  trinitroglycerine  should  be  subjected  to 
rigorous  control ;  the  glycerine  should  be  pure  and  distilled  and  should  satisfy  the  requirements 
indicated  on  p.  222.  The  nitric  acid  should  have  a  specific  gravity  of  1-500  (48°  Be.  or  about 
95  per  cent.  HN03)  and  should  not  contain  more  than  1  per  cent,  of  nitrous  acid  (the  final  mixture 
less  than  0-3  per  cent.),  i.  e.,  it  should  not  be  yellow,  as  otherwise  an  increased  amount  of  heat 
is  evolved  during  nitration  and  the  yield  is  lowered.  The  sulphuric  acid  should  be  pure,  with  a 
sp.  gr.  of  1-8405  (i.  e.,  at  least  96  per  cent.  H2S04)  and  acid  "containing  more  than  0-1  per  cent, 
of  arsenic  should  be  avoided ;  lead  and  iron  should  also  be  absent  as  they  might  lead  to  reduction. 
When  nitrations  are  carried  out  with  nitric-sulphuric  acids  almost  free  from  water  ( 1  to  2  per  cent. ) 
the  sulphuric  acid  is  replaced  by  oleum  or  Nordhausen  acid  (see  Vol.  I.,  p.  317),  i.  e.,  acid  containing  ' 
20  per  cent,  or  more  of  dissolved  sulphur  trioxide. 

According  to  Markovnikov  (1899)  the  sulphuric  acid  first  forms  the  intermediate  product, 
OH  •  SO,  •  ONO,,  with  the  nitric  acid. 


278 


ORGANIC    CHEMISTRY 


of  sulphuric  acid  employed  always  exceeds  that  of  the  nitric  acid  (about  1£  times).  In 
modern  factories  the  following  proportions  are  often  used :  100  kilos  of  glycerine,  240  to 
270  kilos  of  nitric  acid  (96  per  cent.),  and  330  to  360  kilos  of  sulphuric  acid  (96  per  cent., 
partly  oleum). 

In  the  best  factories  the  practical  yield  was  formerly  200  to  210  kilos  of  nitroglycerine 
per  100  of  glycerine.  In  1900,  however,  the  French  works  began  to  make  use  of  highly 
concentrated  acid  mixtures  (the  5  to  6  per  cent,  of  water  being  diminished  to  2  to  3  per 
cent,  by  mixing  oleum  in  place  of  sulphuric  acid  of  66°  Be.  with  the  concentrated  nitric 
acid).  Later  Nathan  and  Bintoul  employed  mixtures  containing  only  1  to  1-5  per  cent, 
of  water,  the  yields  rising  to  225  to  228  per  cent.  Yields  of  232  per  cent,  were  then  obtained 
by  means  of  water-free  mixtures,  from  which  the  nitroglycerine  separates  better  owing  to 
its  less  solubility  and  to  the  greater  difference  in  density.  The  yield  may  be  improved 

still  further  and  the  duration  of  the  nitration  reduced 
to  one-half  by  cooling  the  acid  mixture  during  the 
reaction  by  means  of  brine  from  a  refrigerating 
machine,  the  temperature  being  thus  maintained  at 
about  10°. 

The  highest  yields  appear  to  be  obtained  with  a 
mixture  containing  46  per  cent,  of  HN03  and  54 
per  cent,  of  H2S04  (Hofcoimmer, . -l$12). 

The  low  value  of  the  practical  compared  with 
the  theoretical  yield  (246-7)  is  due  to  the  fact  that 
towards  the  end  of  the  reaction  there  is  very  little 
free  nitric  acid  and  the  last  portions  of  glycerine 
added  are  nitrated  only  with  difficulty,  and  hence 
remain  dissolved  in  the  sulphuric  acid. 

The  mixture  of  nitric  and  sulphuric  acids,  which 
is  prepared  separately,  is  made  by  pouring  the 
sulphuric  acid  slowly  into  the  nitric  acid  (not  vice 
versa)  in  an  iron  vessel,  the  mixture  being  kept 
well  cooled  and  stirred.  With  this  procedure  there 
is  no  danger  of  the  acid  spurting,  and  no  production 
of  nitrous  fumes,  since  the  development  of  heat  is 
gradual.  This  mixture  is  forced  by  means  of 
elevators  (Montejus)  or  pulsometers  working  with 
co-mpressed  air  (Vol.  I.,  p.  302)  into  tanks  which 
feed  the  leaden  apparatus  in  which  the  glycerine  is 
nitrated. 

During  recent  years,  many  vitriol  and  explosives 
works  have   made  considerable  use  of  Kuhlmann 
emulsors  (or  Mammoth  pumps)  for  raising  concen- 
trated acids,  which  are  rendered  lighter  by  emulsifica- 
tion  with  air  (see  illustration,  Vol.  I.,  p.  304). 

The  leaden  nitration  apparatus  is  shown  in  Fig.  193.  It  is  surrounded  by  a  wooden 
jacket  inside  which  water  circulates.  Inside  the  vessel  are  peripheral  leaden  coils  through 
which  large  quantities  of  cold  water  are  continually  passed  by  means  of  the  two  tubes  D. 
The  tubes  G  lead  dry  compressed  air  to  the  bottom  of  the  liquid,  which  is  thus  kept 
thoroughly  mixed.  The  tube  F  serves  as  exit  for  the  air,  and  for  any  nitrous  vapours  which 
may  be  evolved  and  may  be  observed  through  the  window,  / ;  these  vapours  are  recovered  in 
small  condensation  towers  sprinkled  with  a  little  water.  The  cold  acid  mixture  is  first  intro- 
duced through  the  pipe  G.  The  glycerine,  at  a  temperature  of  20°  to  25°  (if  colder  it  would 
be  too  viscous),  is  measured  in  the  reservoir,  M,  and  is  passed,  by  means  of  compressed 
air  supplied  through  O,  slowly  into  the  tube  H,  and  thence  into  a  perforated  circular  pipe 
at  the  bottom  of  the  apparatus.  Two  thermometers,  E,  show  the  temperature  of  the 
reacting  mass  at  any  moment. 

The  bottom  of  the  apparatus  is  slightly  inclined  and  at  the  lowest  part  is  inserted  a 
large  stoneware  tap,  K,  with  an  ebonite  screw  containing  an  aperture  of  at  least  5  cm. 
It  is  convenient  to  have  two  of  these  taps  so  that,  in  case  of  danger,  the  whole  of  the  mass 
may  be  rapidly  discharged  into  a  vessel  of  water  underneath  (drowning  of  the  nitroglycerine). 
In  such  an  apparatus,  the  same  quantity  of  nitroglycerine  is  produced  each  time  and  the 


NITRATION    OF    GLYCERINE 


279 


-pIG 


treatment  of  100  kilos  of  glycerine  requires  less  than  half  an  hour.1    In  America  as  much 

as  2000  kilos  of  glycerine  are  worked  at  one  time  in  open  vessels  provided  with  stirrers, 

but  the  risk,  in  case  of  explosion,  is  greatly  increased.     At  the  conclusion  of  the  operation 

the  nitroglycerine  (sp.  gr.  1-6)  floats  on  the  acids  (sp.  gr.  1-7)  and  is  separated  by  means 

of  a  suitable  decanting  apparatus  (Fig,  194)  to  the  bottom  of  which  the  whole  mass  is 

passed  through  the  tube  K.     The 

apparatus    consists    of    a    leaden 

tank  with  its  base  sloping  towards 

the  centre  and  supported  by  a 

wooden  structure  ;  the  cover,  C,  is 

raised  on  wooden  joists,  B.     The 

tube  Z>,  with  the  glass  window,  E, 

serves  to  carry  off  any  gas  which 

may  be  evolved;  a  thermometer 

is  inserted  into   the   vessel  at  t. 

The  tube  shown   at  the  bottom 

and  in  the  centre  of  the  apparatus 

communicates  with  two  or  three 

taps,  H,  and  is  also  fitted  with  a 

window,  F. 

After  half  an  hour,  the  nitro- 
glycerine in  this  vessel  separates 
into  a  distinct  layer,  as  may  be 
seen  through  /.  The  surface  of 
separation  of  the  two  layers 
coincides  very  nearly  with  the 
tap  J,  so  that  the  nitroglycerine 
may  be  discharged  almost  completely  through  the  tube  J  into  the  lead-lined  wooden 
tank,  L.2  The  acid  that  remains  is  discharged  through  one  of  the  taps,  H,  it  being  noted 

1  Before  the  reaction  is  started  the  acid  mixture  in  the  apparatus  is  cooled  to  15°  to  18°, 
a  stream  of  air  (as  dry  as  possible)  being  passed  through  it  and  cold  water  being  circulated  through 
the  coils.     If  brine  from  an  ice  machine  is  used,  the  temperature  may  be  lowered  to  8°  to  10°. 

The  temperature  during  the  reaction  should  not  exceed  25°  to  30°  (  18°  to  20°  if  brine  is  used), 
and  it  may  be  regulated  by  passing  the  cooling  water  more  or  less  rapidly  through  the  coils, 
and,  if  necessary,  through  the  wooden  jacket;  increase  of  the  air-current  also  helps  to  lower 
the  temperature.  Rise  of  temperature  and  consequent  explosion  were  at  one  time  due  principally 
to  the  use  of  impure  glycerine,  but  nowadays  are  generally  due  to  slight  escape  of  water  from  the 
coils.  In  order  to  avoid  such  danger,  the  apparatus  and  coils  are  tested  at  least  once  a  day, 
usually  in  the  evening,  when  the  plant  is  free  ;  water  under  pressure  is  forced  into  the  coils  and 
jacket  and  left  until  the  morning,  when  any  leak  can  be  detected.  Although  the  apparatus  is 
constructed  of  very  thick  plates,  the  lead  corrodes  in  time  ;  tests  made  with  aluminium  apparatus 
(proposed  by  Guttler)  have  not  been  very  successful.  Some  works  now  employ  more  solid 
vessels  of  wrought-  or  cast-iron,  which  are  more  easily  cooled. 

Boutmy  and  Faucher  (1872)  avoid  the  dangers  of  violent  reactions  by  first  dissolving,  e.  g., 
100  parts  of  glycerine  in  320  of  sulphuric  acid  and  then  pouring  the  solution  into  a  mixture  of 
280  parts  of  nitric  and  280  of  sulphuric  acid.  After  twelve  hours  the  reaction  is  complete,  the 
yield  being  190  per  cent.,  calculated  on  the  weight  of  the  glycerine  taken.  This  method  did 
not  give  good  results  in  England,  but  has  been  applied  in  France.  The  procedure  is,  however, 
irrational,  since  the  operation  occupies  twelve  hours,  the  duration  of  the  contact  of  the  acid 
with  the  nitroglycerine  and  hence  the  danger  period  being  prolonged.  A  factory  using  this 
method  did,  indeed,  blow  up  and  the  process  was  then  abandoned. 

Kurtz  (Ger.  Pats.  6208  and  8493)  increases  the  yield  and  accelerates  the  reaction  by  emulsify- 
ing the  glycerine  with  air  and  passing  it  under  the  acid  mixture,  a  more  intimate  mixture  being 
thus  obtained.  R.  Evers  (Ger.  Pat.  183,183,  1902),  instead  of  mixing  with  a  current  of  air, 
which  always  carries  off  a  little  acid,  passes  the  acid  mixture  and  glycerine  at  the  same  time 
through  a  pulveriser  into  the  apparatus. 

2  Not  infrequently,  owing  to  the  formation  of  a  colloidal  froth  of  silicic  acid,  the  nitroglycerine 
separates  very  slowly  from  the  acids,  two  or  three  hours  being  sometimes  required  for  a  good 
separation  and  the  danger  of  decomposition  thus  increased.     Various  investigations  have  been 
made  with  a  view  to  discover  a  means  of  preventing  such  slow  separation,  which  is  often  due  to 
the  use  of  glycerine  of  poor  quality  or  of  impure  acids.     Good  results  have  been  obtained  by  the 
addition,  before  the  mass  is  discharged  into  the  separator,  of  a  small  quantity  of  sodium  fluosi- 
licate,  the  bubbles  of  hydrofluosilicic  acid  thus  developed  causing  rapid  separation  of  the  nitro- 
glycerine.    Reese  (Brit.  Pat.  20,310,  1905)  adds  at  the  beginning  of  the  reaction,  about  0-002 
per  cent,  of  sodium  fluoride,  calculated  on  the  weight  of  the  glycerine.     According  to  Ger.  Pat. 
249,579  of  1911,  0-02  to  0-05  per  cent,  of  finely  powdered  talc  or  kaolin  (on  the  weight  of  the 
glycerine)  may  be  added  to  the  acid  before  the  reaction  is  started. 


280 


ORGANIC    CHEMISTRY 


through  F  when  a  turbid  layer  appears,  as  this  separates  the  acid  from  the  nitroglycerine 
and  contains  various  nitro-products  and  certain  impurities.1 

The  tap,  H,  is  then  closed  and  this  liquid  is  passed  through  other  taps  into  suitable 
washing  and  decanting  vessels  (see  later).  The  nitroglycerine  in  L  is  .washed  with  water 
and  is  then  agitated  by  passing  compressed  air  through  the  perforated  pipe,  N,  for  about 
fifteen  minutes ;  the  nitroglycerine  is  allowed  to  settle  and  the  water  decanted  off  by  means 
of -the  upper  tap,  M .  The  washing  with  water  is  repeated  two  or  three  times,  all  the  washing 
water  being  collected  in  a  single  tank.2  Finally  the  nitroglycerine  is  passed  into  a  similar 

1  The  acid  separated  from  the  nitroglycerine  and  containing  about  70  to  73  per  cent.  H2S04, 
9  to  10  per  cent.  HNO3,  15  to  16  per  cent.  H2O,  and  3  per  cent,  of  dissolved  nitroglycerine,  is 

•  collected  in  leaden  tanks  in  which  it  remains  for  one  or  two  days,  during  which  time  a  small 
quantity  (about  0-5  per  cent.)  of  nitroglycerine  separates  at  the  surface.  The  dangers  of  this 
slow  separation  are  sometimes  avoided  by  neglecting  the  nitroglycerine  which  separates  after 

four  to  five  hours ;  to  avoid  danger  in 
succeeding  nitrating  operations,  a  large 
proportion  of  the  nitroglycerine  remain- 
ing dissolved  is  decomposed  by  adding 
cautiously  4  to  5  per  cent,  of  water,  so  as 
to  raise  the  temperature  to  35°  to  40° 
and  then  again  mixing  the  mass  by 
means  of  air  (part  of  the  trinitroglycerine 
is  thus  transformed  into  soluble  dinitro- 
gly cerine ).  These  recovered  acids,  which 
are  utilised  again,  are  first  denitrated  in 
the  apparatus  shown  in  Fig.  195.  This 
consists  of  a  tower  A,  4  to  5  metres  high, 
composed  of  six  or  seven  rings  of  volvic 
stone  in  one  piece,  fitted  by  means  of 
grooves  and  luted  with  powdered  asbestos 
and  a  little  sodium  silicate.  The  inner 
and  outer  diameters  are  respectively  30 
to  40  cm.  and  50  to  65  cm.  These  rings 
are  surrounded  by  tightly  fitting  cast- 
iron  hoops.  The  internal  space  is  filled 
with  fragments  of  silica  (quartz),  glass 
or  stoneware,  resting  on  a  grid  of  volvic 
stone  or  earthenware.  The  acid  to  be 
denitrated  passes  from  the  tank  D  down 
***  the  tower  as  a  spray,  while  a  current  of 
FIG.  195.  steam,  superheated  to  about  350°  and 

mixed  with  a  little  hot  air  (at  400°)  is 

passed  in  at  the  bottom  through  the  cock  a.  The  acid  feed  is  regulated  so  that  sulphuric  acid 
at  about  150°  collects  at  the  base  of  the  tower,  while  the  nitric  acid  vapour  issuing  through  the 
tube  C  has  the  temperature  110°  to  120°.  By  introducing  this  hot  mixture  into  the  tower,  steam 
is  economised  and  the  nitric  acid  condensing  in  the  stoneware  pipes  G  is  rendered  more  con- 
centrated (usually  60  to  65  per  cent.,  although  with  care  85  per  cent,  may  be  reached)  and,  if 
sufficient  air  is  used,  contains  little  nitrous  acid  (3  to  5  per  cent.).  The  gases  not  condensed  in 
the  pipes  G  are  completely  condensed  in  the  ordinary  stoneware  .towers  fed  with  a  little  water 
or  dilute  nitric  acid  (see  Vol.  L,  p.  388),  being  passed  from  one  tower  to  the  other  until  acid  of 
32°  to  36°  Be  is  obtained. 

The  sulphuric  acid  at  last  reaches  the  bottom  of  the  tower,  A,  where  it  collects  in  the  basin, 
E,  and  thence  passes  through  the  leaden  cooling  coil,  F.  The  acid  thus  obtained  is  darkened 
by  the  impurities  present  and  has  a  density  of  about  56°  to  58°  Be ;  it  is  usually  concentrated 
in  the  Kessler  apparatus  or  in  Gaillard  towers  (see  Vol.  I.,  p.  308). 

During  recent  years,  instead  of  the  sulphuric  and  nitric  acids  being  recovered  and  concen- 
trated separately,  it  has  been  found  preferable  to  send  the  acid  mixture — after  decomposition 
of  the  dissolved  nitroglycerine  (see  above) — directly  but  carefully  into  the  vessels  (already  con- 
taining the  sodium  nitrate)  in  which  nitric  acid  is  made.  Some  prefer  to  revivify  the  acid  mixture, 
i.e.,  to  bring  it  up  to  its  original  strength  by  adding  the  necessary  quantities  of  fuming  nitric 
and  sulphuric  acids,  so  that  it  may  be  used  again  for  the  production  of  fresh  quantities  of  nitro- 
glycerine ;  for  this  purpose,  sulphuric  anhydride  or  oleum  is  added  slowly  to  the  required  amount 
of  concentrated  nitric  acid  and  the  mixture  then  poured  into  the  weak  acid.  For  this  process  of 
recovering  the  weak  acids  (by  which  the  2-5  per  cent,  or  so  of  nitroglycerine  dissolved  in  the 
acid  is  recovered)  to  be  employed,  a  cheap  supply  of  sulphuric  anhydride  or  oleum  must  be 
available  (oleum  at  less  than  40s.  per  ton ). 

2  The  wash-waters  from  all  the  preceding  operations  are  collected  in  an  inclined  lead-lined 
tank  called  the  labyrinth,  which  is  divided  into  a  number  of  chambers  by  vertical  leaden  walls 
perforated  alternately  at  the  top  and  bottom.     The  wash-waters  enter  slowly  at  one  end  of  the 
tank  and  traverse  a  long  up-and-down  course,  gradually  depositing  the  emulsified  or  suspended 
drops  of  nitroglycerine  before  the  opposite  end  of  the  tank  is  reached.   The  nitroglycerine  collected 
at  the  bottom  is  discharged  through  suitable  taps  and  added  to  that  in  the  washing  apparatus. 


NATHAN-THOMSON    PROCESS 


281 


FIG.  196. 


vat  where  it  is  stabilised,  i.  e.,  washed  alternately  with  very  dilute  soda  solution  and  water 

until  the  wash- water  no  longer  has  an  acid  reaction  towards  litmus  and  the  nitroglycerine 

has  a  feeble  alkaline  reaction 

(0-01    of    alkalinity,    which 

disappears  later). 

In  the  British  Government 

factory  at  Waltham  Abbey, 

Nathan,  Thomson,  and  Rin- 

toul  (Brit.  Pats.  15,983, 1901 ; 

and  3020,  1903)  prepare  nitro- 
glycerine    in     large     leaden 

vessels     (a,    Fig.    196)    with 

inclined  bottoms ;  300  to  500 

kilos  of  glycerine  are  allowed  to  run  into  an  anhydrous  acid  mixture  in  the  proportion  of 

267  kilos  of  H2S04  and  243  kilos  of  HN03  per  100  kilos  of  glycerine,  and  at  the  end  of 

the  operation,  after  50  to 
60  minutes'  rest,  the  acid 
recovered  from  a  preceding 
operation  is  passed  from 
the  tank,  c,  to  the  bottom 
of  a.  In  this  way  the 
nitroglycerine  is  displaced 
and  caused  to  discharge 
through  s  into  the  washing 
vessel,  e,  exit  for  the 
vapours  being  supplied  by 
the  tube  o.  When  all  the 
nitroglycerine  has  been 
forced  out,  a  little  of  the 
acid  mixture  is  drawn  off 
by  the  pipe  i,  2  to  3  per 
cent,  of  water  being  then 
slowly  added  to  the  re- 
mainder, which  is  mixed 
meanwhile  with  a  current 
of  air.  By  this  means  the 
dissolved  nitroglycerine  is 
decomposed  and  the 
dangers  of  slow  separation 
in  any  of  the  vessels  avoided 
(see  preceding  Note).  The 
acid  is  immediately  de- 
nitrated,  after  sufficient  has 
been  passed  into  the  tank, 
c,  to  displace  the  nitro- 
glycerine of  the  succeeding 
operation.  6  is  the  tank  in 
which  fresh  acid  is  mixed, 
/  the  vessel  for  drowning, 
g  that  for  stabilising,  and 
h  the  filter  for  the  nitro- 
glycerine, these  two  being 
at  a  considerable  distance 
from  e,  so  that  the  nitro- 
glycerine  may  be  conducted 
to  them  as  soon  as  it  has 

undergone  its  initial  rough  washing.     The  nitrating  apparatus  is  shown  in  section  in  Fig. 

197.     Yields  of  as  much  as  230  per  cent,  are  obtained  with  this  Nathan-Thomson  process, 

which  is  now  used  in  all  countries. 


282  ORGANIC    CHEMISTRY 

FILTRATION.  The  washed  nitroglycerine  is  carried  in  hardened  rubber  or  ebonite 
buckets  to  the  filters,  which  are  merely  wooden  frames  covered  with  woollen  cloth  or  felt 
to  retain  the  impurities,  scum,  gummy  matters,  etc.  By  covering  these  cloths  with  a 
layer  of  dried  salt,  the  emulsified  water  also  can  be  held  back.  The  cloths  rapidly  become 
blocked  and  are  frequently  renewed.  -The  filtration  is  often,  especially  in  England,  effected 
by  means  of  the  apparatus  shown  in  Fig.  198.  This  consists  of  a  lead-lined  tank,  A,  with 
inclined  base.  In  the  lid  is  inserted  a  leaden  cylinder,  G,  with  a  metal  gauze  bottom  on 
which  rests  a  filtering  cloth,  N,  and  on  this  a  layer  of  sodium  chloride,  0,  covered  by  another 
filtering  cloth  kept  stretched  by  a  leaden  ring,  Q ;  the  free  part  of  this  cloth  is  folded, 
stretched,  and  fixed  by  a  conical  leaden  weight,  S.  In  place  of  salt,  a  sponge  may  be  em- 
ployed to  retain  the  water.  In  some  cases  complete  separation  of  the  water  from  nitro- 
glycerine is  obtained  by  leaving  the  latter  at  rest  for  a  couple  of  days  in  a  tepid  place  (30°) 
and  then  decanting  it,  but  there  is  then  some  risk,  owing  to  the  prolonged  accumulation  of 
large  quantities  of  nitroglycerine. 

In  the  working  of  nitroglycerine,  each  operation  is  usually  carried  out  in  a  separate 
building,  that  in  which  the  explosive  is  produced  being  at  a  very  high  elevation,  the  nitro- 
glycerine then  flowing  to  lower  points  for  the  succeeding  operations.  All  these  buildings 
are  of  wood  so  as  to  diminish  the  damage  in  case  of  explosion.  The  floors  of  the  sheds  in 
which  the  nitroglycerine  is  produced  and  of  those  where  it  is  treated  in  the  liquid  state  are 

covered  with  sheet-lead  with  raised  edges  so 
that  the  material  may  be  caught  in  case  of 
breakage. 

Where  the  nitroglycerine  is  worked  in  a 
pasty  state  (for  dynamites)  the  flooring  is  of 
wood  free  from  crevices. 

If  nitroglycerine  is  accidentally  spilled, 
it  should  be  immediately  wiped  up  with 
sponges. 

The  channels  through  which  nitro- 
glycerine passes  from  one  shed  to  another 
are  in  the  form  of  gutters  furnished  with 
removable  covers  and  are  fitted  with  a 
longitudinal  pipe  through  which  warm  water 
may  be  circulated  in  winter  and  the  danger 
FIG.  198.  of  freezing  avoided.  A  disadvantage  attend- 

ing the  use  of  these  channels  is  that  an 

explosion  in  one  shed  is  propagated  along  the  channels  to  all  the  other  sheds.  Hence 
the  precaution  is  taken  of  disconnecting  one  section  of  a  channel  when  not  in  actual 
use.  In  many  factories  the  nitroglycerine  is  transported  in  rubber  pails  (see  above). 

The  windows  of  the  sheds  are  smeared  with  whitening,  as  the  presence  of  curved  parts 
in  the  naked  glass  might  possibly  result  in  the  focussing  of  light  on  the  explosive  material 
and  in  the  explosion  of  the  latter. 

USES  OF  NITROGLYCERINE.  Small  quantities  are  sometimes  used  in 
medicine  to  induce  dilation  of  the  blood-vessels,  but  practically  the  whole 
of  the  production  is  used  as  an  explosive.  In  America  it  has  been  long  in  use 
in  the  pure  state  for  large  mining  operations ;  Mowbray  freezes  it  and  trans- 
ports it  in  large  quantities  on  trains  from  the  factory  to  the  place  of  consump- 
tion, as  he  regards  it  as  less  sensitive  in  the  frozen  state,  but  this  view  is  generally 
contested.  It  has  also  been  transported  without  danger  in  solution  in  methyl 
or  ethyl  alcohol,  from  which  it  is  re  precipitated  with  water  at  its  destination. 
Almost  all  the  nitroglycerine  made  is  used  in  the  manufacture  of  various  kind 
of  dynamites,  dynamite  gelatines,  explosive  gelatines,  smokeless  powder,  etc. 

DYNAMITES.  This  generic  name  is  given  to  explosives  obtained  by 
gelatinising  or  absorbing  nitroglycerine  by  various  other  substances.  We 
have  already  mentioned  that  Alfred  Nobel,  the  father  of  dynamite,  had  from 
1860-1864  various  explosions  of  nitroglycerine,  sometimes  of  that  recovered 
from  the  alcohol  in  which  it  had  been  transported  (see  above).  In  his  attempts 


DYNAMITES 


283 


to  diminish  the  dangers  of  nitroglycerine  by  diluting  it  with  inert  substances, 
Nobel  discovered  in  1866  that  it  is  absorbed  by  kieselguhr  (infusorial  earth)  x 
in  considerable  proportions  (up  to  81  per  cent.),  and  that  in  this  state  its 
power  is  diminished  but  little,  while  it  can  be  safely  handled  and  transported. 
He  found  further  that  this  dynamite  is  exploded  only  by  means  of  a  fulminate 
of  mercury  cap. 

If  the  absorbing  substances  are  inert,  like  infusorial  silica  (kieselguhr),  sawdust,  cellu- 
lose, etc.,  they  form  dynamites  with  inactive  absorbents,  which  contain  about  72  to  75  per 
cent,  of  nitroglycerine,  24-5  per  cent,  of  kieselguhr,  and  0-5  per  cent,  of  soda  for  the  No.  1 
quality,  and  less  nitroglycerine  (up  to  50  per  cent. )  in  the  Nos.  2  and  3  qualities. 

In  the  new  types  of  dynamite,  however,  the  solid  matter  consists  of  active  substances, 
e.  g.,  nitrocellulose,  which  take  part  in  the  explosion.  These  are  dynamites  with  active 
absorbents,  the  absorbents  or  bases  being  again  divided  into  nitrates  or  inorganic  oxidising 
bases  and  organic  nitro-absorbents  (collodion-cotton,  etc. ). 

I.  MANUFACTURE  OF  DYNAMITE  WITH  INACTIVE  ABSORBENTS.  The 
kieselguhr  used  must  be  suitably  prepared.  It  is  first  spread  out  in  furnace  chambers 
and  gently  heated  to  eliminate  moisture  and  organic  matter,  and  is  then  more  strongly 
calcined  in  reverberatory  or  muffle-furnaces,  excessive  heating,  being  avoided,  as  it  may 
destroy  the  absorbing  properties.  It  is  then  ground  to  fine  powder  and  sieved.  The 
flour  thus  obtained  should  not  contain  more  than  1  per  cent,  of  moisture  and  should  be 
immediately  filled  into  sacks  and  consumed  the  same  day,  as  otherwise  it  might  absorb 
moisture.  It  consists  of  silica  with  traces  of  oxides  of  iron  and  aluminium. 

The  nitroglycerine  is  weighed  in  buckets  of  hard  guttapercha  or  lacquered  wood  and 

1  Kieselguhr  is  found  in  a  very  pure  state  in  the  Liineburg  moors,  near  Unterliiss  in  Hanover, 
at  Oberhohe  near  Ebsdorf  (Prussia),  at  Tiitelwiese  near  Berlin,  at  Bilin  (Bohemia),  and  in  an 
inferior  quality  in  Scotland,  Norway,  and  Italy.  It  consists  almost  exclusively  of  the  siliceous 


FIG.  199. 

remains  of  diatoms,  and  contains  also  traces  of  iron  and  organic  matter.  It  is  unsuitable  if  it 
contains  aluminium  sulphate.  Its  particles  are  formed  of  empty  tubes  perforated  in  all  directions, 
and  it  is  this  structure  which  renders  kieselguhr  so  highly  absorbent.  Under  the  microscope, 
it  presents  the  appearance  shown  in  Fig.  199.  At  the  present  time  kieselguhr  dynamite  has  been 
almost  entirely  replaced  by  new  types  (gums  or  gelatines)  described  later. 

The  kieselguhr  of  Algeria  (Orano)  forms  one  of  the  richest  deposits  known,  its  composition 
being  moderately  constant,  as  is  shown  by  the  following  percentage  compositions  of  two  samples 
(1911): 

H2O  SiOa  NaCl  CaCO3  MgSO4          Impurities 

Orano  type        ...          5-7  72-6  0-3  14-8  2-2  4-2 

Cherchell  type   ...          6-1  80-4  0-2  4-4  1-6  8-1 

In  1914  a  deposit  of  a  million  tons  was  found  in  Chili. 


284 


ORGANIC    CHEMISTRY 


is  carefully  taken  to  the  mixing -Jwuse,  where  it  is  poured  into  wooden  troughs  lined  with 
sheet-lead,  and  containing  the  absorbent.  Skilled  workmen  then  mix  the  mass  rapidly  by 
hand ;  sometimes  rubber  gloves  are  worn,  but  usually  the  men  prefer  to  do  without  gloves, 
as  the  hands  become  accustomed  to  the  action  of  the  nitroglycerine  in  two  or  three  days. 
It  is  important  to  obtain  a  homogeneous  mixture,  so  that  not  the  least  portion  of  the 
kieselguhr  remains  free  from  nitroglycerine.  After  this  hand-mixing  the  mass  is  rubbed 
through  brass-wire  sieves  (2  to  3  meshes  per  centimetre)  arranged  above  lead-lined  wooden 
troughs.  The  dynamite  is  placed  on  the  sieve  with  a  wooden  spatula  and  pressed  through 
with  the  palm  of  the  hand;  here,  too,  the  use  of  rubber  gloves  is  not  popular  with  the 
operatives.  In  the  troughs  the  dynamite  is  in  the  form  of  fine  grains,  which  should  not  be 
too  dry  or  too  greasy.  If  too  dry,  it  is  passed  again  through  the  sieve  or  mixed  with  more 
nitroglycerine,  whilst  if  too  greasy  it  is  mixed  with  a  further  amount  of  kieselguhr.  It  is 
then  placed  in  small  portions  in  rubber  bags  or  in  wooden  boxes  lined  with  sheet-zinc  and 
is  removed  to  the  building  where  the  cartridges,  used  especially  in  mines,  are  prepared. 
Here  the  dynamite  is  transformed  by  simple  presses  into  rolls,  19,  23,  or  26  mm.  in  diameter. 
A  very  simple  press  devised  by  0.  Guttmann  is  shown  in  Fig.  200.  The  dynamite  is  intro- 
duced into  the  cloth  bag,  m,  and  falls  into  the  tube,  I,  being  pressed  into  this  by  the  lignum 

vitae  or  ivory  piston,  p,  at  the  end  of  the  bar,  d,  which 
is  actuated  by  the  lever,  i;  the  cylinder  of  dynamite 
issuing  from  the  bottom  of  the  tube,  I,  is  broken  by  hand 
into  definite  lengths,  which  are  wrapped  in  parchment 
paper  or  waxed  paper.  The  ordinary  length  is  10  cm. 
(discharge  cartridges)  or  2-5  to  5  cm.  (primers).  These 
cartridge  machines  are  sometimes  worked  by  pulleys 
and  motors.  In  some  cases  the  boudineuses  illustrated 
later  are  used.  After  the  dynamite  is  wrapped  up, 
packets  of  2-5  kilos  are  placed  in  cardboard  boxes, 
which  are  wrapped  and  tied  round  and  filled  in  tens  into 
wooden  cases.  For  military  purposes  the  cartridges  are 
put  directly  into  metal  boxes  with  a  socket  in  the  lid 
for  inserting  the  detonator.  For  use  under  water  these 
metal  boxes  are  sometimes  used,  and  sometimes  sausage- 
skins  or  rubber  bags. 

These  cartridge  buildings  are  usually  small,  with 
light  walls  and  roof ;  only  two  or  three  operatives  work 
in  "each,  high  earthen  banks  separating  one  building 
from  the  next,  so  that  the  effects  of  an  explosion  may 
be  mitigated. 

Dynamite  containing  70  to  75  per  cent,  of  nitro- 
glycerine is  known  commercially  as  dynamite  No.  1  and  those  with  50  per  cent,  and  30  per 
cent,  as  No.  2  and  No.  3  respectively. 

In  place  of  kieselguhr  various  other  absorbents  are  used  at  the  present  time,  e.  g.,  wood 
meal  (cellulose)  mixed  with  inert  mineral  salts  (calcium  carbonate,  sodium  bicarbonate,  etc. ). 
First  in  America  and  then  in  Austria  fulgurite  was  prepared  with  60  per  cent,  of  nitro- 
glycerine, the  remaining  40  per  -cent,  consisting  of  wheaten  flour  and  magnesium  carbonate. 
At  Cologne,  Miiller  prepared  a  Wetter-dynamite  (safety  dynamite,  for  use  in  mines  containing 
firedamp;  see  later)  by  mixing  10  parts  of  ordinary  dynamite  with  7  parts  of  crystalline 
sodium  carbonate;  the  water-vapour  formed  on  explosion  surrounds  the  flame  and  the 
explosive  gases  and  thus  prevents  explosion  of  the  firedamp.  Many  varieties  of  these 
dynamites  are  used  to  a  greater  or  less  extent  in  practice,  e.  g.,  carbodynamite,  containing 
90  per  cent,  of  nitroglycerine  and  10  per  cent,  of  carbonised  cork,  sebastine,  lithodastite, 
carbonite,  etc.  (see  later,  pp.  307,  311). 

Properties  of  Dynamite  with  Inert  Bases.  This  forms  a  pasty  mass  of  reddish  yellow, 
red,  or  grey  colour  according  to  the  quality  of  the  infusorial  earth  employed;  to  ensure 
a  uniform  colour  about  0-25  per  cent,  of  burnt  ochre  is  often  added.  It  is  odourless  and 
has  the  sp.  gr.  14  and  the  pasty  consistency  of  wet  modelling  clay ;  the  inside  of  the  wrapper 
should  show  no  traces  of  nitroglycerine  (sweating).  It  is  much  less  sensitive  to  pressure 
and  percussion  than  nitroglycerine  and,  in  small  portions,  may  be  lighted  and  burned 
without  exploding. 


FIG.  200. 


NITROCELLULOSE  285 

It  can,  however,  be  exploded  by  powerful  percussion  or  detonation,  or  by  red-hot 
metal,  or  by  heating  suddenly  to  a  high  temperature  or  for  a  long  time  at  70°  to  80°. 
Dynamite  freezes  at  temperatures  below  -f-  8°  and  then  becomes  less  sensitive ;  before 
being  used  it  must  be  carefully  thawed  in  warming-pans,  surrounded  by  water  at  a  tem- 
perature not  exceeding  60° ;  it  must  never  be  thawed  on  a  heated  metal  plate.  Thawed 
dynamite  should  be  used  carefully,  as  a  little  nitroglycerine  exudes  during  thawing.  Most 
of  the  dynamite  made  is  used  as  an  explosive  in  mines  and  for  firearms ;  for  cannon  it 
has  little  use,  owing  to  the  danger  caused  by  sweating  during  the  thawing,  so  that  for 
military  purposes  explosives  are  used  which  are  safer  to  transport  and  not  so  sensitive  to 
shock  or  to  discharge  (explosion  by  influence). 

For  non-congealing  dynamites,  see  note  on  p.  276. 

II.  DYNAMITES  WITH  ACTIVE  BASES,  (a)  Pulverulent  Dynamites  with 
Inorganic  Nitrates.  Immediately  after  the  discovery  of  dynamite  with  a  silica  base  came 
the  idea  of  replacing  the  inactive  substance,  which  diminished  the  force  of  the  nitrogly- 
cerine, by  active  substances,  so  that  the  explosive  power  of  the  dynamite  might  be 
increased. 

In  America  such  dynamites  are  often  made  with  40  per  cent,  of  nitroglycerine,  45  per 
cent,  of  sodium  nitrate,  14  per  cent,  of  wood-pulp,  and  1  per  cent,  of  magnesium  carbonate ; 
these  dynamites  are  well  suited  for  mines  where  no  great  power  but  considerable  safety  is 
required.  In  Europe  mixtures  of  nitroglycerine,  ammonium  nitrate,  fine  sawdust,  sodium 
nitrate,  carbon,  etc.,  are  made;  e.g.,  20  per  cent,  nitroglycerine,  36  per  cent,  sodium 
nitrate,  25  per  cent,  ammonium  nitrate,  18-5  per  cent,  roasted  rye  flour,  and  0-05 
per  cent.  soda. 

In  Austria  Trauzl  in  1867  prepared  a  pasty  mixture  of  nitroglycerine  with  guncotton, 
which  was  not  affected  by  water  and  was  exploded  only  by  fulminate  of  mercury  detonators. 
This  product  was  not  successful,  but  similar  and  improved  preparations  were  subsequently 
made. 

About  this  time  Abel  in  England  prepared  glyoxiline  by  soaking  defibred  guncotton 
and  potassium  nitrate  in  nitroglycerine ;  this  also  was  unsuccessful. 

(b)  Blasting  Gelatine  and  Gelatine  Dynamite.  Since  these  contain  nitrocellulose, 
they  will  be  mentioned  later  (see  Smokeless  Powders,  p.  294),  after  the  manufacture  of 
nitrocellulose  has  been  described. 

Statistics  of  dynamite  :   see  later,  at  the  end  of  the  chapter  on  Explosives. 

Various  attempts  have  been  made,  but  without  practical  success,  to  use  nitro-deriva- 
tives  of  carbohydrates  as  explosives.  Mention  may  be  made  of  :  nitromannitol,  discovered 
almost  simultaneously  early  in  1847  by  Flores  Domont  and  Menard  and  by  Ascanio  Sobrero, 
who  named  it  fulminating  mannitol  and  obtained  it  in  a  similar  manner  to  nitroglycerine. 
It  is  composed  mainly  of  hexanitromannitol,  C6H8(ONO2)6,  which  consists  of  white  crystals 
melting  at  112°  to  113°,  while  the  crude  product,  containing  tetra-  and  penta-nitromanni- 
tols,  melts  at  80°;  it  dissolves  to  some  extent  in  alcohol  (1-35)  and  better  in  ether  (1-24), 
and  has  the  density  1-6  or,  when  compressed,  1-8.  It  is  a  shattering  explosive,  highly 
sensitive  to  shock. 

NITROSTARCH  could  not  formerly  be  obtained  sufficiently  nitrated,  but  octonitroslarch, 
C12H12010(N02)8,  containing  nearly  16-5  per  cent,  of  nitrogen,  may  be  prepared  by  the 
process  of  Hough  of  New  York  (Ger.  Pat.  172,549,  1903,  improved  later);  this  consists  in 
treating  the  starch  with  a  mixture  of  3  parts  of  95  per  cent  nitric  acid,  2  parts  of  98  per 
cent,  sulphuric  acid  and  sufficient  S03  to  yield  an  anhydrous  mixture  containing  2  per 
cent,  of  free  SO3,  a  further  quantity  of  oleum  with  2  per  cent,  of  free  SO3  being  added 
during  the  nitration.  It  appears  that  nitrostarch  was  tried  as  a  military  explosive  in  the 
United  States  prior  to  the  European  War. 

NITROCELLULOSE 
(Guncotton  or  Pyroxyline  and  Collodion-Cotton) 

This  substance  should,  to  be  in  order,  be  described  later,  after  cellulose 
(which  is  a  carbohydrate  with  many  alcoholic  groups  and  with  a  molecular 
formula  polymeric  with  C6H10O5)  has  been  studied,  but  as  its  properties  and 


286  ORGANIC    CHEMISTRY 

uses  are  closely  connected  with  those  of  explosives,  it  is  considered  opportune 
to  include  it  in  the  present  section.1 

CONSTITUTION  OF  NITROCELLULOSE.  The  relation  CnH2mOm  of  the  com- 
ponents of  cellulose  being  expressed  by  the  more  simple  formula  (C6H10O5)n  it  is  found  that 
the  maximum  degree  of  nitration  consists  in  the  introduction  of  three  nitric  acid  residues  per 
molecule  of  C6H10O6,  so  that  guncotton  was  given  the  name  trinitrocellulose,  and  was  repre- 
sented by  the  formula  C6H705(N02)3.  Since  the  use  of  more  dilute  acids  results  in  the 
combination  of  a  less  proportion  of  nitric  acid  residues,  it  is  supposed  that  a  mononitro- 
and  a  dinitro-cellulose  are  also  formed. 

It  was  found  later  by  Eder  that  there  exist  nitrocelluloses  with  compositions  intermediate 
to  those  of  tri-  and  di-nitrocelluloses,  and  others  between  the  mono-  and  di-nitro-compounds, 
so  that  it  must  be  supposed  that  cellulose  has  a  formula  at  least  double  that  of  the  simple 
one  given  above,  but  the  mononitrocellulose  corresponding  with  this  doubled  formula 
C12H20O10,  L  e.,  (C6H10H5)2,  has  not  yet  been  prepared. 

Still  later  Vieille,  by  accurate  study  of  the  nitrocelluloses  prepared  with  acids  of  various 
concentrations,  succeeded  in  preparing  eight  different  types  of  nitrocellulose,  this  result 
indicating  that  Eder's  formula,  which  predicted  only  six,  could  no  longer  serve.  Vieille 
then  proposed  for  cellulose  a  formula  double  that  of  Eder,  i.  e.,  C^H^Ogo  or  (C6H1005)4, 
according  to  which  twelve  nitrocelluloses  are  theoretically  possible;  eight  of  these,  from 
endeca-  to  tetra-nitrocellulose  have  been  actually  prepared.  Mendeleev,  having  found 
nitrocelluloses  intermediate  to  or  identical  with  these  twelve,  but  different  from  those 
studied  by  Vieille  in  being  soluble  in  a  mixture  of  alcohol  and  ether,  proposed  the  doubling 
of  Vieille's  formula,  so  that  cellulose  becomes  C^H^O^  or  (CyS^O^g.  To-day,  however, 
it  is  thought  that  these  differences  are  due  to  mechanical  mixtures  of  the  various  nitro- 
celluloses rather  than  to  separate  chemical  compounds,  and  further,  that  the  nitration 
is  gradual  and  leads  from  the  more  simple  to  the  more  complex  forms. 

1  In  1833  Braconnot  observed  that  when  starch  or  wood  is  treated  with  concentrated  nitric 
acid,  a  mucilaginous  solution  is  obtained  which,  on  addition  of  water,  yields  a  white  powder 
soluble  in  a  mixture  of  alcohol  and  ether;  this  powder,  which  burns  vigorously,  he  called  xyloidin. 

In  1837,  by  immersing  cellulose  (flax,  cotton,  paper,  etc.),  for  a  few  seconds  in  concentrated 
nitric  acid  and  washing  it  immediately  with  a  large  quantity  of  water,  so  that  it  retains  its  original 
fibrous  form,  Pelouze  obtained  a  product  which  is  highly  inflammable  and  explodes  on  percussion ; 
he  regarded  it  as  xyloidin  (in  reality  it  was  guncotton),  and  recommended  it  for  making  fireworks. 

In  1846,  Schonbein  at  Basle,  and  some  months  later,  and  independently,  Bottger  at  Frankfort 
discovered  that  the  nitration  of  cellulose  takes  place  much  more  easily  and  completely  if  the 
cotton  is  treated  with  a  mixture  of  concentrated  nitric  and  sulphuric  acids  (industrially  this 
method  was  used  in  1846  by  Hofmann  and  by  Muspratt).  In  order  to  utilise  industrially  the 
guncotton  thus  obtained,  the  two  discoverers  combined  and  kept  their  process  secret.  After 
the  initial  difficulty  in  getting  this  new  explosive  taken  up  in  practice,  the  extraordinary  power 
of  guncotton  and  its  great  advantages  over  black  powder  aroused  considerable  enthusiasm. 
Scarcely,  however,  had  it  come  into  general  use  in  various  countries  than  a  number  of  spontaneous 
and  fatal  explosions  in  guncotton  factories  and  magazines,  by  which  whole  buildings  were  razed 
to  the  ground,  created  such  a  panic  that  its  manufacture  was  everywhere  abandoned.  The 
process  of  nitration  was  then  already  known  to  Knop  and  Karmarsch,  and  to  others,  who  manu- 
factured guncotton  by  this  simple  process.  In  1846,  Sobrero  made  use  of  the  nitric-sulphuric 
mixture  for  the  preparation  of  nitroglycerine. 

In  1853,  the  Austrian,  Captain  von  Lenk,  ascertained  how  to  render  guncotton  safe.  The 
Austrian  Government  acquired  from  Schonbein  and  Bottger  the  process  of  manufacture  (at  a 
price  stated  to  be  30,000  florins,  or  £2500)  and  maintained  the  secret  of  avoiding  the  spontaneous 
decomposition  of  guncotton  until  1862.  Then  von  Lenk  communicated  the  secret  to  the  French 
and  English  Governments,  and  in  1864  patented  the  process  in  America.  Whilst  in  America 
the  manufacture  was  undertaken  on  an  enormous  scale,  in  Austria  and  England  it  was  again 
suspended  on  account  of  further  terrible  explosions  in  the  factories  themselves;  these  were 
explained  by  the  English  workers  as  due  to  the  insufficient  purification  of  the  nitrocellulose  by 
von  Lenk.  In  1865,  Abel  discovered  the  method  of  bestowing  absolute  safety  and  keeping 
qualities  on  the  nitrocellulose.  He  used  first  of  all  the  process  of  washing  proposed  in  1862 
by  the  Englishman  J.  Tonkin,  which  consisted  simply  in  complete  washing  with  abundant  supplies 
of  water;  the  nitrated  cotton  was  then  defibred  or  pulped  in  "  hollander  "  machines  similar  to 
those  employed  in  paper  factories  and  the  wet  pulp  subjected  to  considerable  pressure.  From 
that  time  the  manufacture  extended  to  all  countries,  in  spite  of  an  English  factory  being  blown 
up  in  1871  (apparently  a  criminal  act),  and  in  recent  times  it  has  acquired  new  and  increased 
importance  owing  to  the  discovery  of  smokeless  powder. 

The  process  universally  used  at  the  present  time  in  the  manufacture  of  guncotton  is  that 
indicated  by  Abel.  Before  the  discovery  of  smokeless  powder,  guncotton  had  limited  applications 
and  was  not  used  in  mines,  since,  in  the  form  in  which  it  was  prepared,  it  had  an  excessive 
shattering  action,  whilst  in  mines  progressive  explosives  are  usually  required. 


GUNCOTTON  287 

Nitrocelluloses  with  more  than  12-83  per  cent,  of  nitrogen  were  at  one  time  regarded 
as  being  insoluble  in  alcohol-ether,  but  Abel  showed  that  there  are  nitrocelluloses  with 
13-2  per  cent,  of  nitrogen  and  still  soluble  in  this  mixture,  whilst  others  with  only  12-8  per 
cent,  are  insoluble,  and  that  this  depends  on  the  method  of  preparation — the  duration  of 
action  of  the  mixed  acids,  the  ratios  and  concentrations  of  the  latter,  and  the  temperature 
at  which  they  act — and  on  the  nature,  purity,  and  dryness  of  the  cotton.  Only  by  following 
exactly  the  directions  is  it  possible  to  obtain  a  constant  percentage  of  nitrogen  and  complete 
solubility  or  insolubility  in  the  mixture  of  alcohol  and  ether. 

It  was  also  once  thought  that  guncotton  was  a  nitro-compound  in  the  true  sense  of  the 
word,  i.  e.,  that  the  N02  groups  were  united  directly  to  carbon,  but  first  Bechamp  and 
then  others  showed  that  it  is  a  true  nitric  ester  which  can  be  saponified,  with  regenera- 
tion of  the  cellulose,  by  alkalis,  alkaline  salts,  ammonium  sulphide,  or  ferrous  chloride. 
It  has  been  further  shown  that  with  the  maximum  of  nitrogen  an  oxynitrocellulose  is 
obtained  [oxycellulose  is  (C6H1006)3  +  (C6H1006)n,  so  that  the  nitrocellulose  will  be 
C6H7(N02)3O5  +  C6H7(N02)306,  and  this  with  ferrous  chloride  gives  oxycellulose;  nitro- 
mannitol,  treated  similarly,  gives  mannitol  and  not  oxymannitol]. 

PROPERTIES  OF  GUNCOTTON.  Under  the  microscope  nitrocellulose 
has  the  same  appearance  as  ordinary  cotton,  but  in  polarised  light  it  appears 
iridescent.  When  moistened  with  a  solution  of  iodine  in  potassium  iodide 
and  then  with  sulphuric  acid,  nitrocellulose  becomes  yellow  and  cellulose  blue. 
It  is  somewhat  less  white  than  ordinary  cotton,  is  rather  rough  to  the  touch  and 
crackles  when  pressed  with  the  fingers ;  it  becomes  electrified  when  rubbed  and 
then  appears  phosphorescent  in  the  dark.  It  is  soluble  in  ethyl  acetate  (as 
shown  by  Hartig  in  1847),  nitrobenzene,  benzene,  acetone,  etc.,  but  insoluble 
in  water,  alcohol,  ether,  acetic  acid  or  nitroglycerine,  although  a  mixture  of 
nitroglycerine  and  nitrocellulose  is  soluble  in  acetone,  forming  a  jelly,  cordite 
(see  later). 

It  resists  the  action  of  dilute  acids,  but  is  decomposed  slowly  by  concen- 
trated sulphuric  acid  or  hot  alkali,  and  is  completely  dissolved  by  hot  sodium 
sulphide.  Decomposition  is  also  effected  by  iron  and  acetic  acid  or  by 
ammonium  sulphide  or  ferrous  chloride  (Bechamp). 

Flocculent,  loose  guncotton  has  the  sp.  gr.  0*1,  whilst  the  powder  (pulp) 
has  the  sp.  gr.  0*3  and  is  exploded  by  shock  or  percussion  only  at  the  point 
where  it  is  struck,  the  explosion  not  being  propagated  to  the  whole  mass.  When 
ignited,  it  burns  so  rapidly  that  even  when  it  is  placed  on  black  powder,  the 
latter  does  not  burn. 

In  the  form  of  cord,  it  burns  more  slowly  and  may  be  used  as  a  rapid  fuse. 
When  wet  or  compressed  it  has  a  specific  gravity  varying  from  1  to  1'3  (the 
absolute  sp.  gr.  is  1*5)  and  it  then  burns  slowly  and  cannot  be  exploded  by 
percussion  or  by  ordinary  detonators ;  explosion  can,  however,  be  induced  by 
detonating  a  little  dry  guncotton  with  a  fulminate  of  mercury  cap.  The 
shattering  power  diminishes  with  increase  of  the  density,  which  reaches  a 
maximum  on  gelatinisation  (see  later  :  Progressive  Smokeless  Powders).  The 
decomposition  proceeds  according  to  the  equation  : 

2C6H702(ONO2)3  =  5CO  +  7C02  +  8H  +  3H20  +  6N. 

Less  compressed  guncotton  gives  more  CO  and  H  in  comparison  with  the  C02 
and  H20,  and  hence  has  a  less  effect,  the  development  of  heat  being  smaller. 
No  ash  or  smoke  is  formed,  and  1  kilo  of  guncotton  yields  741  litres  of  gas  (the 
water  being  liquid,  or  982  litres  if  the  water  is  in  the  state  of  vapour),  which  is 
inflammable  and,  owing  to  the  presence  of  carbon  monoxide,  poisonous.  The 
temperature  of  combustion  has  been  given  as  6000°  (i.  e.,  1071  Cals.  is  developed 
by  1  kilo),  and  in  practice  exceeds  4000°  and  may  produce  a  pressure  of  15,000 
atmos. 

Unless  guncotton  is  carefully  prepared,  it  undergoes  gradual  change  and 
may  explode  spontaneously,  especially  in  the  light,  and  to  this  are  probably 


288  ORGANIC    CHEMISTRY 

due  the  great  explosions  which  occurred  formerly  (1848-1862).  Even  dry, 
granulated  guncotton  becomes  harmless  and  safe  to  handle  if  it  is  immersed 
for  a  moment  in  ethyl  acetate,  as  it  becomes  coated  with  a  gelatinous  layer 
which  dries  and  preserves  it,  if  moist,  from  further  evaporation. 

Guncotton  is  transported  in  large  quantities  in  the  wet  state  in  wooden 
boxes  placed  in  others  of  zinc  which  are  sealed  hermetically  to  retain  the 
moisture.  It  is  stored  in  dry  magazines  which  are  situate  at  least  150  (better 
500)  metres  from  any  habitation  and  are  not  surrounded  by  earthworks  so 
that  the  more  serious  effects  due  to  projection  of  debris  may  not  be  added  to 
those  of  an  explosion 

MANUFACTURE  OF  GUNCOTTON.  Hanks  of  purified  cotton,  free  from  impurities, 
are  employed.  This  cotton  should  fulfil  certain  requirements.1 

In  place  of  cotton  it  is  economical  in  some  cases  to  use  filter- paper,  unsized  paper,  parch- 
ment paper  or  paper  cellulose,  but  such  substances  are  less  convenient  than  cotton  as  they 
easily  undergo  pulping  to  an  almost  pulverulent  mass,  which  leads  to  losses  and  requires 
different  conditions  for  nitration. 

The  pure  cotton  is  placed  loose  on  trays  which  are  arranged  in  a  drying-stove  heated 
by  means  of  gilled  pipes  through  which  steam  circulates;  the  heating  is  continued  until 
the  proportion  of  moisture  is  less  than  0-5  per  cent.,  after  which  the  cotton  is  allowed  to  cool 
for  twelve  to  fifteen  hours  in  hermetically  sealed  boxes.  If  not  pure  the  cotton  is  best 
defatted  by  boiling  it  for  two  to  three  minutes  with  2  per  cent,  sodium  hydroxide  solution ; 

it  is  then  washed  with  water  and  subsequently  treated 
with  very  dilute  nitric  acid  in  the  hot.  In  some  cases 
it  is  also  bleached  with  a  weak  solution  of  hypo- 
chlorite,  well  rinsed  with  water  and  dried  in  a  hot-air 
oven  at  100°  to  115°  as  above.  When  almost  dry  it 
is  carded,  dried  completely,  and,  while  still  hot,  placed 
in  hermetically  sealed  boxes  so  that  no  more  moisture 
may  be  absorbed. 

Nitration  is   then   effected   with   a   mixture   of 
concentrated  nitric  and  sulphuric  acid,  as  follows  : 

FIG.  201.  3  parts  of  pure  sulphuric  acid  of  sp.  gr.  1-840  (95-6 

per  cent. )  are  poured  into  1  part  of  pure  nitric  acid 

of  sp.  gr.  1-500  (95  per  cent.),  mixing  taking  place  immediately  and  completely  without 
the  aid  of  stirrers.  In  this  way  a  mixture  containing  about  72  per  cent,  of  H2SO4,  23-5 
per  cent.  HN03,  and  4-5  per  cent.  H20  is  obtained.  If  the  acid  mixture  contains  much 
nitrous  acid,  it  may  yield  cellulose  nitrite,  which  contains  only  2-5  per  cent,  of  nitrogen,  is 
insoluble  in  acetone  and  is  less  stable  than  ordinary  nitrocellulose  (Nicolardot  and  Chertier, 
1910). 

The  mixture  is  then  delivered  with  the  help  of  an  acid  elevator  (Monlejus)  into  the 
nitration  apparatus,  consisting  of  a  cast-iron  vessel,  A  (dipping  pot)  (Fig.  201),  standing 
in  a  larger  vessel,  G,  through  which  cold  water  circulates  from  H  to  J.  The  cotton  is  im- 
mersed in  small  portions  (300  to  800  grams)  in  the  acid-bath  and  is  stirred  with  an  iron 
fork.  In  England  1  kilo  of  cotton  is  used  per  160  kilos  of  the  acid  mixture,  while  in  Germany 
1  kilo  of  cotton  is  taken  for  every  40  kilos  of  acid ;  after  a  short  time  (fifteen  to  thirty  minutes ) 
the  nitrated  cotton  is  removed  with  iron  forks  and  is  placed  to  drain  on  a  cast-iron  grid 

1  Cotton  for  nitrocellulose  should  be  pure  white  and  should  not  contain  dust  or  fibres  of  jute, 
hemp,  or  flax,  or  woody  matter  or  pods;  these  impurities,  when  separated  by  hand  from- 200 
grams  of  the  cotton,  should  not  exceed  0-5  gram.  The  filaments  should  not  be  too  short,  other- 
wise they  form  a  paste  during  nitration.  A  small  piece  thrown  into  water  should  sink  in  two 
minutes.  It  should  not  contain  more  than  0-9  per  cent,  of  substances  soluble  in  ether  (fats,  etc. ) ; 
in  many  factories  0-5  per  cent,  is  not  allowed.  In  England  the  amount  of  fat  allowed  is  1-1  per 
cent,  extracted  with  ether  in  four  hours  in  a  Soxhlet  apparatus  (see  Analysis  of  Fats).  The 
moisture,  determined  by  heating  the  cotton  in  an  oven  at  100°  until  its  weight  remains  constant, 
should  not  exceed  6  per  cent,  and  the  cotton  merchant  is  debited  with  any  excess  and  also  with 
the  cost  of  drying. 

When  moistened  with  a  few  drops  of  water,  the  cotton  should  maintain  a  neutral  reaction. 

The  ash,  estimated  by  heating  a  few  grams  of  the  cotton  to  redness  in  a  platinum  capsule 
until  it  becomes  quite  white  and  of  constant  weight,  should  not  amount  to  more  than  0-3  per  cent. 


NITRATION    OF    COTTON 


289 


(grate),  B  and  C,  arranged  on  one  side  above  the  vessel ;  before  it  is  taken  away,  it  is  pressed 
with  a  cast-iron  plate,  F,  connected  with  a  lever,  D  E. 

The  acid  mixture  is  renewed  when  it  has  treated  30  to  50  per  cent,  of  its  weight  of  cotton ; 
also  after  each  portion  of  cotton  is  removed  from  the  bath,  fresh  acid  mixture,  equal  to 
ten  times  the  weight  of  the  cotton  taken  out,  is  added  in  order  to  make  up  for  what  has  been 
absorbed  and  combined.  On  the  German  system  (where  less  acid  is  used)  renewal  takes 
place  more  frequently.  Above  each  of  the  nitrating  vessels  is  a  hood  with  a  strong  draught 
to  carry  off  the  nitrous  vapours  which  are  always  evolved.  Excessive  rise  of  temperature 
or  use  of  weak  acid  mixtures  (with  more  than  9  per  cent,  of  water)  gives  »guncotton  which 
contains  less  nitrogen  and  is  not  completely  soluble  in  alcohol-ether,  as  is  required  in  practice. 

In  some  factories  the  nitration  is  carried  out  in  a  number  of  small,  deep  and  narrow, 
hemispherical  vessels  of  cast-iron  mounted  on  trolleys.  These  are  charged  in  order  with 
certain  weights  of  acid  mixture  (30  to  50  kilos)  and  dry  cotton  (2  to  4  kilos),  and,  after 
thorough  mixing,  the  trolleys  are  pushed  into  an  oblong  lead-lined  chamber  provided  with 
as  many  doors  as  there  are  trolleys.  A  powerful  aspirator  draws  the  nitrous  vapours  into 
a  wooden  flue.  A  battery  of  soaking-pots  is  used  in  such  a  way  that  when  the  last  is  intro- 
duced into  the  chamber  the  first  has  already  finished  reacting  (thirty  to  forty  minutes), 
and  as  the  pots  are  of  metal  and  relatively  small  and  are  in  a  strong  draught,  the  heat 
developed  is  readily  dispersed.  The  pots  are  removed  from  the  chamber  and  taken  to  the 


FIG.  202. 


FIG.  203. 


neighbouring  centrifugal  machines,  into  which  the  contents  of  the  pots,  which  are  mounted 
on  pivots,  are  tipped.  The  centrifuges  are  similar  to  those  employed  in  sugar  factories  (see 
Sugar)  and  have  a  steel  or  leaded  steel  rotating  basket ;  aluminium  ones  have  also  been  tried, 
but  not  with  great  success.  A  few  minutes'  centrifugation  at  900  to  1000  revolutions  per 
minute  removes  the  greater  part  of  the  acid  from  the  guncotton ;  the  latter  is  immediately 
taken  to  the  washing  machines,  while  the  acid  recovered  is  revivified  in  the  manner  described 
on  p.  280.  If  drops  of  water  or  lubricating  oil  fall  on  to  the  cotton  during  centrifugation, 
the  mass  sometimes  undergoes  sudden  decomposition  with  formation  of  a  dense  cloud  of 
brown  vapour ;  this  does  not  constitute  a  serious  danger,  since  usually  it  is  not  accompanied 
by  explosion. 

In  some  factories  the  nitration  is  nowadays  carried  out  directly  in  the  centrifuges,  which 
may  be  of  naked  or  leaded  steel  or  even  of  earthenware,  although  these  are  heavier  and 
more  fragile  (see  Figs.  202,  203).  The  latter  consist  of  a  double- walled  earthenware  basket, 
the  inner  wall,  d  and  a,  but  not  the  outer  one,  being  perforated ;  the  two  walls  being  a  slight 
distance  apart,  an  annular  space,  c,  is  left,  which  has  an  outlet  above  in  a  number  of  holes, 
s,  in  the  edge  of  the  bush.  The  whole  is  bound  with  steel  hoops,  t,  to  prevent  danger  from 
projection  in  case  of  fracture.  The  dry  cotton  (7  to  8  kilos  or  more)  is  arranged  peripher- 
ally inside  the  perforated  basket,  the  acid  being  supplied  by  the  tube,  ra;  the  basket,  sur- 
rounded by  the  jacket,  b,  and  the  cover,  z,  both  of  earthenware,  is  set  in  motion  by  the 
shaft,  p,  driven  by  the  belt,  r.  The  acid  is  driven  uniformly  through  the  cotton  by  centri- 
fugal force,  rises  through  the  ring  space,  c,  and  issues  from  the  holes,  s,  into  the  channel,  e, 
whence  a  pipe,  /,  carries  it  to  an  elevator  to  be  circulated  again.  The  operation  is  of  short 

VOL.  n.  19 


290 


ORGANIC    CHEMISTRY 


duration,  and  the  red  vapours  are  emitted  from  the  tube,  g.  During  nitration,  the  velocity 
of  the  drum  is  relatively  low,  but  at  the  end  the  velocity  is  increased ;  the  nitrated  cotton 
can  then  be  taken  away  at  once  to  be  washed. 

Use  is,  however,  preferably  made  of  steel  centrifuges  with  circulation  of  the  acid,  as 
proposed  by  Selwig  and  Lange;  the  basket,  d,  is  perforated  (Fig.  204)  and  the  cover  is  of 
aluminium  and  hinged,  and  is  furnished  with  a  large  tube,  o,  communicating  with  the  pipe 
of  an  aspirator,  n.  The  basket  is  moved  slowly  and  filled  with  the  nitric-sulphuric  mixture 
(e.  g.,  70  per  cent.  H2SO4,  23  per  cent.  HNO3  and  7  per  cent,  water)  up  to  the  top  edge; 
the  cotton  is  then  introduced  in  packets  (1  kilo  per  40  to  50  kilos  of  acid)  and  the  basket 
given  a  velocity  of  20  to  30  turns  per  minute.  This  movement  causes  the  acid  to  circulate 
continuously  through  the  cotton,  and  in  half  an  hour  the  nitration  of  6  to  8  kilos  of  cotton 
is  complete;  the  acid  is  then  discharged  and  the  velocity  increased  to  remove  as  much 
acid  as  possible  from  the  cotton,  which  is  taken  out  and  washed  in  the  ordinary  way.  Use 
is  now  made  of  centrifuges  1  to  1-1  metres  in  diameter,  and  14  to  18  kilos  of  cotton  are 
nitrated  at  a  time. 

Sometimes,  especially  in  summer,  the  nitrocellulose  decomposes  in  the  centrifuge  itself, 


FIG.  204. 

producing  vast  columns  of  reddish-brown  vapour;  as  a  rule,  not  explosion,  but  merely 
deflagration  occurs.  Such  decomposition  takes  place  the  more  readily  at  the  end  of  the 
centrif ugation,  especially  if  this  is  unduly  prolonged  or  excessively  rapid ;  often  the  cause 
is  the  spurting  of  water  or  lubricant  into  the  centrifuge,  but  it  may  be  the  presence  of 
impurities  in  the  cotton  or  a  workman  spitting  into  the  centrifuge. 

Since  August  1905  in  the  Royal  Gunpowder  Factory  at  Waltham  Abbey  (where  2000 
tons  are  produced  per  annum),  guncotton  has  been  made  by  the  displacement  process  of 
J.  M.  and  W.  Thomson,  improved  by  Nathan,  which  is  briefly  as  follows  (Ger.  Pat.  172,499, 
1904). 

Into  the  earthenware  basins,  which  have  perforated  double  bottoms  and  aluminium 
covers  (Fig.  205)  and  are  connected  in  groups  of  four  by  means  of  leaden  pipes 
and  also  communicate  with  an  exhauster,  G,  600  litres  of  the  nitric-sulphuric  mixture 
is  placed;  about  10  to  12  kilos  of  cotton  is  then  introduced  in  small  portions  into  each 
vessel  and  pressed  with  perforated  stoneware  discs  divided  into  septa  so  that  the  acid 
exactly  covers  the  cotton  and  scarcely  fills  the  orifices  of  the  discs ;  a  layer  of  water  about 
1  cm.  deep  is  then  cautiously  introduced  on  to  the  perforated  disc,  which  separates  the 
cotton  and  acid  from  the  superposed  water  and  thus  prevents  the  two  liquids  from  mixing, 
the  fumes  being  largely  absorbed  by  the  water. 

The  nitration  lasts  about  two  and  a  half  hours,  and  at  the  end  water  is  introduced  above 
the  perforated  plate,  this  displacing  at  the  bottom  a  corresponding  quantity  of  the  acid ; 
the  acid  thus  recovered  (90  per  cent.)  is  reinforced  with  oleum  and  strong  nitric  acid.  The 
displacement  lasts  three  hours,  after  which  the  mass  is  centrifuged  and  the  cotton  washed, 
rendered  stable,  pulped,  etc. 


WASHING    OF    NITROCELLULOSE 


291 


Since  guncotton  should  have  a  very  definite  nitrogen  content,  different  from  that  of 
collodion-cotton  used  to  gelatinise  nitroglycerine  (see  later),  the  process  of  nitration  is  care- 
fully followed  by  numerous  rapid  analyses  until  suitable  conditions  are  found  for  obtaining 
a  constant  product ;  after  this  has  been  done,  the  final  control  is  sufficient.  It  has  been 
proposed  to  follow  the  extent  of  nitration  of  cellulose  by  observing  its  behaviour  towards 
polarised  light.  In  recent  years  it  has  been  shown  that  guncotton  of  more  constant  type 
and  more  readily  rendered  stable  is  obtained  if  the  acid  mixture  is  renewed  for  each  nitration ; 
the  last  processes  described 
are  hence  to  be  preferred. 

There  has  been  much 
discussion  concerning  the 
relative  suitability  .  of 
centrifuges  and  Nathan- 
Thomson  vessels  for  nitra- 
tion. It  now  seems  estab- 
lished that,  even  in  the 
latter,  either  guncotton  or 
collodion-cotton  may  be 
prepared,  provided  that 
the  conditions  of  the  re- 
action, the  temperature, 
the  time,  and  the  concentration  and  composition  of  the  acids  are  suitably  and  thoroughly 
studied.  The  plant  of  a  works  using  centrifuges  is  the  more  expensive,  requires  the  greater 
upkeep  expenses  and  contaminates  the  air  with  acid  fumes. 

The  nitrocotton  obtained  by  the  Thomson  process  is  the- more  stable,  since  the  dis- 
placement of  the  acid  by  water  is  accompanied  by  slight  heating,  which  allows  of  the  decom- 
position of  the  unstable  secondary  products  and  the  elimination  of  the  sulphonitric  cellulose. 

For  the  economical  working  of  the  Thomson  process,  the  earthenware  vessels  must  be 
of  good  quality,  so  as  to  avoid  breakages ;  such  vessels  are  now  easily  procurable.  With  the 


FIG.  205. 


Fia.  206. 

centrifuge  system  concentrated  acid  is  recovered,  but  part  of  it  is  lost ;  with  the  Thomson 
vessels  the  whole  of  the  acid  is  recovered,  but  about  25  per  cent,  of  it  is  diluted  with  20  to 
25  per  cent,  of  water  and  has  to  be  denitrated. 

The  degree  of  nitration  and  the  stability  of  nitrocotton  may  be  estimated  by  measuring 
the  viscosity  of  its  solutions,  nitro-oxycelluloses  giving  more  fluid  solutions  than  nitro- 
cellulose. Nitro-oxy cellulose  has  little  stability  and  is  formed  from  cotton  which  has  been 
highly  bleached  with  chlorine  prior  to  nitration  (Picst,  1913). 

The  theoretical  yield  of  dry  guncotton  is  185  kilos  per  100  kilos  of  dry  cotton ;  in  practice 
170  to  175  kilos  is  obtained. 

WASHING.  The  nitrocellulose  from  the  centrifuge  is  passed  directly  into  the  oval- 
washing  vessel  (see  Fig.  206),  which  has  a  longitudinal  partition  down  the  middle  (like 
the  hollander  machines  used  in  paper-making),  and  in  which  a  shaft  furnished  with  beaters 


292 

mixes  the  whole  mass  with  water ;  the  latter  is  constantly  renewed  and  the  washing  con- 
tinued until  the  acid  reaction  towards  litmus  paper  disappears  (two  to  three  hours).  The 
washed  guncotton  is  either  centrifuged  again  or  put  to  drain  in  wooden  baskets.  Although 
it  no  longer  exhibits  an  acid  reaction,  yet,  as  was  shown  by  J.  Tonkin  in  1862  and  by  Abel  in 
1865  (in  England),  it  still  contains  acid,  or  rather  unstable  sulphuric  esters,  in  the  small 
channels  of  its  fibres. 

To  separate  these  remaining  traces  of  acid,  the  nitrocellulose  is  rendered  stable  by  the 
Robertson  system,  which  consists  in  boiling  it  for  two  consecutive  periods  of  twelve  hours 
each  with  water  in  wooden  vats  fitted  with  perforated  false  bottoms  (one  vat  holds  even  more 
than  1000  kilos  of  the  cotton),  beneath  which  steam  is  passed.  Then  follow  four  more 
boilings  of  four  hours  each  with  water  (formerly  one  or  two  boilings  with  calcium  carbonate 
were  also  carried  out),  and  finally  two  or  three  boilings  each  of  two  hours  with  fresh  water. 
This  system  of  washing,  which  lasts  altogether  thirty-six  to  forty-eight  hours,  is  preferable 
to  that  in  which  the  boilings  are  short  at  the  beginning  and  long  at  the  end,  and  especially 
to  that  where  boiling  with  soda  is  interposed,  as  the  soda  hydrolyses  the  nitrocellulose  and 
transform  it  partially  into  collodion-cotton  poor  in  nitrogen  and  soluble  in  alcohol-ether. 
In  France  boilings  of  sixty  to  eighty  or  even  one  hundred  hours  are  employed. 

Some  of  the  boiling  may  be  dispensed  with  if  the  nitrocellulose  is  steamed  in 
closed  vats. 

In  1911,  Baschieri  simplified  the  Robertson  system  by  boiling  the  nitrocellulose  (roughly 
washed  and  centrifuged)  for  two  hours  in  0-05  per  cent,  sulphuric  acid  solution,  then  washing 
twice  in  cold  water,  boiling  for  two  hours  with  0-1  per  cent,  sodium  carbonate  solution, 
and  finally  washing  twice  with  cold  water.  By  this  method  the  nitrocotton  is  rendered 
ready  for  pulping  with  a  minimum  loss  of  nitrogen,  the  maximum  stability  being  thirty- five 
minutes  at  70°  or,  with  the  Abel  test,  135°.  The  acid  bath  serves  especially  for  the  elimina- 
tion of  the  unstable  and  soluble  sulphonitric  celluloses. 

PULPING.  In  spite  of  all  the  washing  and  boiling  to  which  it  is  subjected,  the  gun- 
cotton  persistently  retains  a  trace  of  acid,  and  to  remove  this,  the  cotton  is  thoroughly 
defibred  (pulped)  as  was  proposed  by  Tonkin  and  by  Abel  in  1865.  This  operation  .s  carried 
out  in  hollanders  similar  to  those  used  for  the  preceding  washing  and  identical  with  those 
used  in  the  manufacture  of  cellulose  for  paper  (see  later,  section  on  Paper,  for  figures  and 
cross-sections). 

Pulping  lasts  from  five  to  eight  hours,  according  to  the  fineness  required,  but  if  it  is 
incomplete,  inconveniences  are  met  with  in  the  subsequent  compression,  the  desired  density 
not  being  attainable;  also  if  pulping  is  carried  too  far,  the  compression  is  disturbed  in 
another  way.  Guttmann  proposed  the  use  of  hot  water  in  pulping,  and  this  possesses 
several  advantages  in  addition  to  saving  time.  In  the  large  hollanders,  as  much  as  600  to 
800  kilos  of  guncotton  can  be  treated  at  one  time.  In  some  cases  a  little  calcium  carbonate 
is  added  to  guncotton  to  preserve  it  and  to  neutralise  any  residual  acid ;  it  is  added  in  powder 
just  before  the  completion  of  pulping,  but  its  use  is  not  to  be  recommended,  as  it  tends 
gradually  to  produce  slight  decomposition  of  the  nitrocellulose. 

STABILISING.  Guncotton  (and  also  collodion-cotton)  thus  prepared  does  not  usually 
answer  the  rigorous  tests  to  which  it  is  subjected  (see  later,  Tests  of  Stability),  and  is  ren- 
dered stable  by  again  boiling  it  for  some  hours  with  water  in  large  wooden  tanks  (sometimes 
lined  with  lead),  jets  of  steam,  and  also  of  air  to  keep  the  mass  moving,  being  passed  in  for 
eight  to  twelve  hours.  By  mixing  in  this  way  the  nitrocottons  from  different  nitrations, 
a  mass  is  obtained  which  is  perfectly  homogeneous,  even  as  regards  nitrogen  content,  this 
being  difficult  to  achieve  otherwise. 

In  order  to  separate  the  water,  the  mass  is  placed  in  suitable  centrifuges  fitted  with 
drums  of  fine  metal  gauze  entirely  surrounded  by  linen ;  in  other  cases,  the  water  is  separ- 
ated as  in  paper-mills,  by  placing  the  mass  in  chambers  having  perforated  brass  floors 
covered  with  cloth,  the  pulp  drained  in  this  way  being  finally  centrifuged.  The  water 
separated  from  the  pulp  is  allowed  to  stand  in  suitable  vessels  to  deposit  the  finer  fibres 
it  has  carried  away.  After  centrifugation,  the  pulp  contains  about  25  to  30  per  cent,  of 
water  and  in  this  state  it  can  be  kept  safely  in  zinc  boxes,  in  which  it  can  be  transported 
if  it  is  slightly  compressed  and  the  cover  of  the  box  soldered;  in  moist  wooden  boxes  or 
in  paper  wrapping  nitrocotton  readily  becomes  coated  with  mould.  If  properly  prepared, 
guncotton  should  not  contain  more  than  3-5  to  4  per  cent,  of  collodion-cotton  (soluble  in 
alcohol-ether),  but  in  England  7  to  8  per  cent,  is  allowed.  Excessively  prolonged  boiling 


COMPRESSION    OF    GUNCOTTON 


293 


increases  the  proportion  soluble  and  lowers  somewhat  the  nitrogen  content;  immoderate 
action  of  alkali  produces  a  little  hydronitro cellulose. 

COMPRESSION  OF  GUNCOTTON.  For  military  purposes,  that  is,  for  cartridges 
and  for  the  blocks  used  for  charging  torpedoes,  the  still  moist  guncotton  is  strongly  com- 
pressed, to  render  it  safer  and  more  powerful  owing  to  the  increased  charging  density  (see 
above),  which  reaches  the  value  1-2  with  pressures  of  500  to  1000  atmos.  or  1-35  with  still 
greater  pressure.  Fig.  207  shows  in  section  a  Taylor  and  Challen  hydraulic  press  used 
for  this  purpose;  this  is  set  up  in  an  isolated  room  and  can  be  controlled  from  a  distance 
so  as  to  avoid  any  great  amount  of  damage  in  case  of  explosion  during  the  compression, 
this  mostly  happening  if  any  hard  foreign  body  chances  to  be  present  in  the  guncotton. 

To  obtain  the  greatest  density,  the  pulp  is  first  washed  with  hot  water  and  slightly 
compressed  in  the  mould,  d,  by  means  of  the  lever,  h,  the  water  being  drawn  away  under 
the  perforated  base,  c  (covered  with  steel  gauze),  by  a  pump  connected  with  the  tube,  b. 
The  partitions,  I,  are  raised  and  the  mould  passed  through  an  aperture  in  the  wall,  M  (which 
serves  as  a  protection  for  the  workmen),  and  thus  above  the  plate,  n,  of  the  hydraulic  press ; 
this  plate  is  kept  horizontal  by  four  columns,  $'.  The  mould  is  raised  by  the  piston,  t, 


FIG.  207. 


of  the  press  so  that  it  is  pressed  against  a  die,  r,  fixed  to  the  cover,  q.  This  cover  is  held 
fast  by  the  four  columns  so  that  the  die  penetrates  the  mould  and  compresses  the  cotton 
under  a  pressure  of  800  to  1000  atmos.  The  degree  of  humidity  after  the  compression  is 
about  12  to  14  per  cent.,  and  at  each  operation  a  block  of  1  kilo  is  made,  the  shape  being 
adapted  to  that  of  the  projectile.  Thus  compressed,  guncotton  is  so  hard  and  compact  that 
it  can  be  worked  quite  safely  with  the  plane,  saw,  or  boring  tool,  a  fine  jet  of  water  being 
directed  at  the  point  where  the  cutting  is  taking  place.  To  prevent  compressed  guncotton 
from  losing  moisture  and  from  becoming  mouldy,  it  is  dipped  in  molten  paraffin  wax,  or, 
better,  it  is  immersed  for  a  moment  in  ethyl  acetate  (or  acetone),  which  dissolves  a  little 
nitrocellulose  at  the  surface  and  forms  a  kind  of  impermeable  varnish. 

Since  1898,  in  some  large  works  charges  have  been  prepared  in  a  single  piece,  either 
for  grenades  or  for  torpedoes,  etc.,  by  means  of  the  powerful  press  devised  by  Rollings 
(Brit.  Pat.  23,449,  1899). 

USES  OF  GUNCOTTON.  Until  1890,  moist  compressed  guncotton  had  replaced  all 
other  explosives  for  the  charging  of  torpedoes.  It  is  used  also  for  filling  grenades,  which 
are  then  covered  with  molten  paraffin  wax  to  unite  the  grenade  and  the  explosive ;  explo- 
sion is  effected  by  a  detonator  of  dry  guncotton.  It  is  made  also  into  compressed  cartridges 
for  use  in  mines,  a  cavity  being  left  for  the  detonating  cap  and  the  fuse. 

Since  1890,  guncotton  as  a  high  explosive  for  military  purposes  has  been  replaced  gradu- 
ally and  advantageously  by  picric  acid  and  trinitrotoluene  (T.N.T. ),  which  are  melted  and 


294  ORGANIC    CHEMISTRY 

poured  directly  into  the  projectiles,  bombs,  mines,  etc.  During  the  European  War  all 
the  old  stocks  of  guncotton  were  consumed,  use  being  afterwards  made  solely  of  these 
aromatic  nitro-derivatives  and  of  various  mixtures  of  them  (see  later). 

Mixtures  of  granulated  guncotton  and  nitrates  are  placed  on  the  market  under  the 
names  of  tonite,  potentite,  etc.  Abel  obtained  beautiful  pyrotechnic  effects  by  saturating 
guncotton  with  solutions  of  various  mineral  salts  capable  of  imparting  different  colours 
to  the  flame.  Guncotton  is  sometimes  used  for  filtering  acids,  alkalis,  and  solutions  of 
permanganate,  being  resistant  to  these  reagents  in  the  cold.  Also  it  is  employed  in  some 
cases  as  an  electrical  insulator  and  for  bandaging  purulent  sores  and  wounds,  being  first 
saturated  with  potassium  permanganate. 

COLLODION-COTTON  FOR  GELATINE  DYNAMITE,  DYNAMITE,  AND 
SMOKELESS  POWDERS.  During  the  last  fifty  years,  a  different,  less  nitrated  nitro- 
cellulose, collodion-cotton,  has  assumed  very  great  importance  in  the  manufacture  of  smoke- 
less explosives.  On  the  other  hand,  guncotton  itself  has,  of  late  years,  been  largely  replaced 
by  compressed,  crystalline,  or  fused  trinitrotoluene,  or  by  picric  acid  (see  Part  III),  especially 
for  military  and  naval  purposes.  Collodion-cotton  was  at  one  time  thought  to  be  dinitro- 
cellulose,  soluble  in  a  mixture  of  alcohol  and  ether,  but  it  has  now  been  shown  to  be  a  mixture 
of  various  soluble  nitro-compounds,  which  are  formed  under  conditions  different  from  those 
yielding  guncotton.  Collodion-cotton  should  have  a  constant  nitrogen-content,  and  it 
should  be  readily  soluble  (to  the  extent  of  at  least  95  per  cent.)  in  a  mixture  of  alcohol  (1 
part)  and  ether  (2  parts),  giving  a  dense  viscous  solution;  this  solubility  may,  however, 
be  increased  by  prolonged  heating  under  pressure  with  water  acidified  with  sulphuric  acid, 
which  permits  of  the  preparation,  from  this  collodion-cotton,  of  artificial  silk  better  than 
the  Chardonnet  variety  (Chandelon,  Ger.  Pat.  255,067,  1911-1912).  Collodion-cotton 
is  soluble  also  in  dichlorohydrin  (p.  257). 

If  it  answers  these  requirements,  it  gelatinises  nitroglycerine  well  and  dissolves  completely 
in  it ;  attention  is,  however,  also  paid  to  the  time  necessary  for  gelatinisation. 

For  photographic  plates,  extensive  use  was  formerly  made  of  ethereal- alcoholic  solutions 
of  soluble  nitrocellulose  (collodion),  and  in  this  case  importance  was  attached  not  so  much 
to  the  viscosity  as  to  the  proportion  of  nitrocellulose  which  would  yield  an  elastic  film  of 
marked  resistant  properties.  For  this  purpose,  the  nitration  is  carried  out  at  a  temperature 
of  at  least  40°  to  50°,  so  that  the  resulting  collodion  is  less  viscous ;  also  the  nitrocellulose 
is  not  pulped. 

The  cotton  is  immersed  for  sixty  minutes  or  longer  in  a  mixture  of  1  part  of  95-5  per 
cent,  sulphuric  acid  (sp.  gr.  1-840)  and  1  part  of  75  per  cent,  nitric  acid  (sp.  gr.  1-442)  (this 
mixture  contains  48  per  cent,  of  H2SO4,  37-5  per  cent,  of  HNO3,  and  14-5  per  cent,  of  H20), 
at  a  temperature  of  about  40°. 

The  more  concentrated  the  acid  and  the  more  prolonged  its  action,  the  higher  will  be 
the  nitrogen- content,  but  the  viscosity  will  not  be  decreased ;  a  high  temperature,  however, 
results  in  diminution  of  the  proportion  of  nitrogen  and  also  of  the  viscosity. 

More  commonly  nitration  is  carried  out  in  the  cold  in  the  manner  described  for  making 
guncotton,  only  the  composition  of  the  acid  mixture  being  modified :  with  a  content  of 
22, to  25  per  cent,  of  nitric  acid,  guncotton  is  obtained  if  the  acid  mixture  contains  less  than 
10  per  cent,  of  water  and  collodion- cotton  if  more  than  10  per  cent,  of  water  (up  to  15  to  18 
per  cent. ),  according  to  the  desired  nitrogen  percentage  and  solubility  in  alcohol-ether. 

To  the  International  Congress  of  Applied  Chemistry,  London,  1910,  Saposhnikov  com- 
municated a  series  of  interesting  investigations  (1906-1909)  on  the  practical  conditions 
required  to  establish  beforehand  the  type  of  the  resulting  nitrocellulose  (percentage  of 
nitrogen  and  solubility),  the  results  being  expressed  as  curves  referred  to  triangular 
co-ordinates. 

After  nitration  collodion-cotton  intended  for  the  manufacture  of  gelatine  dynamite 
goes  through  all  the  operations  of  washing,  pulping,  and  boiling  employed  with  guncotton. 
Collodion-cotton  for  gelatine  dynamite  or  smokeless  powder  must  be  subjected  to  a 
drying  process,  while  for  smokeless  powders  the  water  is  expelled  in  another  way.  Since 
the  centrifuged  pulp  still  contains  30  per  cent,  of  water,  whilst  nitrocellulose  begins  to 
decompose  at  70°  (or  even  at  50°  if  badly  prepared)  and  in  the  dry  state  is  very  sensitive 
to  shock  or  percussion,  the  drying  of  collodion-cotton  constitutes  a  very  dangerous  opera- 
tion. At  one  time  it  was  dried  by  means  of  indirect  steam  on  iron  plates  heated  to  40°  to 
50°,  but,  using  the  ordinary  precautions,  it  may  be  dried  on  cloths  in  a  current  of  warm  air. 


SMOKELESS    POWDERS 


295 


When  dry,  it  sometimes  becomes  electrified  on  rubbing,  or  even  by  an  air  current,  and  this 
phenomenon  explains  the  frequent  spontaneous  fires  formerly  occurring  in  the  drying  ovens. 
Guttmann  prefers  to  dry  the  collodion-cotton  on  copper  plates  connected  with  the  earth 
by  wires  (to  discharge  the  electricity).  These  plates  are  perforated  with  conical  holes 
0-25  mm.  wide  at  the  top  and  1  mm.  at  the  bottom ;  strips  of  leather  are  used  to  prevent 
rubbing  of  the  metal  parts.  In  these  ovens,  the  pulp  is  spread  out  and  is  subjected  to  the 
action  of  a  current  of  air  heated  to  40°  (in  some  cases,  also  dried :  see  p.  272 ),  and  in  two 
days  the  mass  is  dry,  not  more  than  0-1  per  cent,  of  moisture  being  then  present.  The 
dried  material  is  then  carefully  placed  in  rubber  bags  and  stored  in  air-tight  boxes. 

The  drying  ovens  are  provided  with  alarm-thermometers,  which  also  regulate  the 
temperature  automatically. 

The  workmen  should  wear  rubber  boots  with  copper  nails  and  in  the  Waltham 
Abbey  Factory  the  leather  transmission  belts  are  soaked  in  glycerine  to  prevent  their 
electrification. 

Drying  in  a  vacuum  is  also  employed  (especially  with  fulminate  of  mercury  and  smoke- 
less powders),  and  is  then  more  rapid  and  takes  place  at  a  lower  temperature,  while 


FIG.  208. 

the  danger  of  an  explosion  is  diminished  owing  to  the  absence  of  the  tamping  effect  of  the 
atmospheric  pressure  (see  p.  264). 

One  of  the  commonest  dryers  working  under  reduced  pressure  is  shown  in  Fig.  208; 
it  is  fitted  with  cloths  and  has  double  walls  to  allow  of  the  circulation  of  steam,  hot  air, 
or  hot  water  (see  also  p.  297 ). 

Collodion- cotton  for  making  ballistite  (see  later)  should  contain  11-75  to  11-95  per  cent, 
of  nitrogen,  whilst  that  for  ordinary  gelatine  dynamites  contains  as  much  as  12  per  cent., 
almost  completely  soluble  in  alcohol-ether. 

The  distinction  between  collodion-cotton  and  guncotton  on  the  basis  of  the  percentage 
of  nitrogen  present  is  not  a  rigorous  one,  since  it  was  shown  by  Roscoe  (during  the  lawsuit 
in  1893  between  the  British  Government  and  Nobel  concerning  the  ballistite  patent)  that, 
by  suitable  modification  of  the  quantity  of  water  and  of  the  ratio  between  the  nitric  and 
sulphuric  acids  in  the  nitrating  mixture,  a  nitrocellulose  which  contains  12-83  per  cent, 
of  nitrogen  and  is  soluble  in  alcohol-ether,  or  one  which  contains  12-73  per  cent,  of  nitrogen 
and  is  insoluble,  may  be  obtained. 

SMOKELESS  POWDERS.  Even  50  years  ago  attempts  were  made  to  diminish  the 
smoke  produced  by  ordinary  gunpowder  by  diminishing  the  amount  of  sulphur  present, 
but  its  relations  to  the  nitre  and  carbon  cannot  be  greatly  altered.  Potassium  nitrate  was 


296  ORGANIC    CHEMISTRY 

then  replaced  by  ammonium  nitrate,  but  this  was  found  to  be  too  hygroscopic ;  yet  later, 
ammonium  picrate  was  employed  with  better,  but  still  not  satisfactory,  results.  In  1864 
Schulze  prepared  a  smokeless  powder  from  nitrocellulose  obtained  from  pure  wood-cellulose. 
It  gave  good  results  with  sporting  guns,  but  was  too  shattering  for  use  in  warfare,  and  the 
same  was  the  case  with  a  smokeless  powder  prepared  in  1882  by  Walter  Reid  by  granulating 
nitrocellulose  and  gelatinising  it  superficially  with  alcohol  and  ether. 

The  true  solution  of  this  important  problem  is  due  to  Vieille,  who  in  1884  found  that  the 
shattering  action  of  guncotton  could  be  transformed  into  a  progressive  (or  propellant)  action 
by  destroying  the  fibrous  structure  with  suitable  solutions.  To  attenuate  the  rapidity  of 
explosion  of  guncotton  it  must  be  made"  as  dense  as  possible  (theoretically  the  fibre  free 
from  interstices  has  the  density  1-5),  and  this  cannot  be  done  practically  with  fibrous  cotton 
(even  when  pulped )  as  a  pressure  of  4000  atmospheres  would  be  necessary.  Vieille,  however, 
dissolved  or  gelatinised  the  nitrocellulose  and  then  recovered  it  by  evaporating  the  solvent ; 
thus  was  prepared  powder  B,  the  first  military  smokeless  powder. 

With  the  smokeless  powder  prepared  by  Vieille  in  1885  the  velocity  of  projectiles  from 
cannon  was  increased  by  100  metres  per  second  over  that  obtained  with  ordinary  powder, 
the  pressure  in  the  cannon  being  the  same  in  the  two  cases ;  hence  guns  of  smaller  calibre 
could  advantageously  be  employed.  This  amounted  to  a  revolution  in  the  region  of  ballistics . 
The  gelatinisation  is  effected  by  solvents  of  nitrocellulose,  i.  e.,  by  ether,  acetone,  ethyl 
acetate,  nitroacetylglycerine,  tetra-  and  penta-chloroethane,  etc.  (see  p.  122). 

SMOKELESS   PROGRESSIVE   POWDERS 

SMOKELESS  POWDERS  OF  PURE  NITROCELLULOSE :  POWDER  B.  Powder 
B  was  applied  in  France  as  a  military  explosive  in  1886,  and  was  used  solely  as  a  propellant 
powder  up  to  the  outbreak  of  the  European  War.  During  the  war  ballistite  (see  later)  also 
was  made  in  France  and  powder  B  in  Italy,  Great  Britain  and  America,  the  French  process 
being  employed ;  briefly  this  is  as  follows  :  By  means  of  a  suitable  k'neading  machine  an 
intimate  mixture  is  made  of  66  to  70  parts  of  guncotton  (known  in  France  as  CP  1 ),  and 
30  to  34  parts  of  moist  collodion- cotton  (termed  CP  2)  (with  about  25  to  30  per  cent,  of 
moisture).  The  moisture  is  not  removed  by  drying  in  an  oven,  which  would  be  dangerous, 
but  is  displaced  by  means  of  95  per  cent,  alcohol  (Messier  process,  1892)  in  suitable  hydraulic 
presses ;  each  chamber  is  charged  with  about  27  kilos  (calculated  dry)  of  mixed  nitrocellu- 
lose, which  is  supported  on  a  perforated  metallic  disc  on  the  bottom  of  the  chamber.  After 
the  moist  cotton  has  been  pressed  slightly  with  the  piston,  about  18  kilos  of  alcohol  is  intro- 
duced and  forced  through  the  cotton,  gradually  displacing  the  water,  which  is  discharged 
through  the  apertures  at  the  base  and  is  followed  by  dilute  and  then  by  concentrated  alcohol ; 
when  the  latter  issues  with  its  original  density,  the  whole  of  the  water  has  been  displaced. 
About  two-thirds  of  the  alcohol  recovered  has  a  concentration  of  about  50  per  cent,  and, 
after  direct  distillation  to  separate  it  from  suspended  cotton  and  from  part  of  the  water, 
is  rectified  to  bring  it  to  95  per  cent,  strength  to  be  used  in  succeeding  operations  (about 
5  per  cent,  of  the  alcohol  is  lost  in  each  operation). 

The  nitrocotton  remaining  in  the  press  is  extracted  by  means  of  a  counter-piston,  which 
forces  it  upwards  in  cakes  impregnated  with  10  to  11  kilos  of  alcohol  (per  27  kilos  of  dry 
nitrocotton).  The  operation  in  each  chamber  occupies  five  minutes. 

These  multiple  dehydration  presses  with  continuous  automatic  action  produce  up  to 
12  to  15  tons  of  dehydrated  nitrocotton  per  day,  the  best  form  being  made  by  Messrs. 
Champigneul  (Paris). 

In  some  powder  B  factories,  instead  of  Champigneul  presses  (which  before  the  war  cost 
about  £1600  and  during  the  war  as  much  as  £6000),  use  is  made  of  hydro-extractors,  the 
nitrocotton  (40  to  45  kilos)  in  the  moving  centrifuge  being  treated  with  a  spray  of  95  per 
cent,  alcohol.  Each  centrifuge  with  a  perforated  drum  1  metre  in  diameter  and  a  final 
velocity  of  1100  revolutions  per  minute  gives  an  output  of  1600  kilos  of  dehydrated  nitro- 
cotton per  twenty-four  hours.  Almost  twice  as  much  alcohol,  however,  is  consumed  in 
the  centrifuges  as  in  the  presses  and  the  percentage  loss  is  greater ;  one-half  of  the  alcohol 
is  recovered  at  about  68  per  cent,  strength  and  the  rest  at  40  to  50  per  cent. ;  the  latter  is 
distilled  and  rectified  and  the  former  used  for  the  first  treatment  in  a  subsequent  operation, 
being  then  recovered  at  40  to  50  per  cent,  strength ;  a  second  treatment  of  the  nitrocotton 
with  95  per  cent,  alcohol  yields  68  per  cent,  alcohol. 


POWDER    B 


297 


Gelatinisation  of  the  nitrocotton  is  effected  most  completely  and  rapidly  with  a  mixture 
of  66  per  cent,  of  ether  and  34  per  cent,  of  alcohol,  i.  e.,  2  vols.  of  ether  and  1  vol.  of  alcohol 
(135  kilos  of  the  mixture  for  100  kilos  of  nitrocotton  calculated  dry),  account  being  taken 
of  the  alcohol  already  present  in  the  nitrocotton.  The  materials  are  thoroughly  kneaded 
in  a  kneading  machine,  the  mass  being  afterwards  discharged  into  zinc  tubs  and  there  left, 
hermetically  sealed,  for  twenty-four  hours  for  the  completion  of  the  gelatinisation. 

By  means  of  hydraulic  presses  similar  to  those  used  for  food  pastes,  the  pasty  mass 
is  converted  into  strips  or  ribbons  varying  from  3  to  6  cm.  in  width  according  to  the  type 
of  powder  and  about  1mm.  in  thickness.  The  ribbons  are  cut  into  lengths  of  about  2  metres, 
hung  on  rods  and  dried  in  a  current  of  air  at  40°,  the  alcohol  and  ether  being  recovered  with 
the  help  of  freezing  machines  (see  note  on  p.  231).  The  strips,  still  containing  25  per  cent, 
of  solvent,  are  then  cut  to  the  desired  width  and  length  (usually  15  to  20  cm.)  and  after- 
wards dried  on  brass  gauze  for  five  to  six  hours  at  55°  to  60°  in  a  stream  of  air,  from  which 
a  little  solvent  may  be  recovered. 


FIG.  209. 

In  some  works  this  drying  is  effected  under  reduced  pressure  (see  Fig.  208),  special 
apparatus  being  used  for  the  recovery  of  the  solvent,  as  shown  in  Fig.  209 ;  P  represents 
the  pump  which  evacuates  the  condensation  chamber  of  the  solvent  C,  this  communicating 
with  the  oven  E.  The  vapours  from  the  wide  tube  at  the  top  of  the  oven  are  condensed 
in  C  by  means  of  a  bundle  of  tubes  through  which  water  is  circulated  by  the  pump  A,  The 
warm  water  from  the  top  of  the  condenser  is  heated  in  the  coil  tank  R  and  then  circulates 
in  the  oven.  The  condensed  solvent  is  collected  in  S  and  rectified. 

The  ribbons,  which  still  contain  about  10  per  cent,  of  solvent,  are  next  placed  vertically 
in  compact  bundles  in  cases  which  are  immersed  for  eight  or  nine  hours  in  vessels  of  water 
at  50°.  The  water  discharged  from  the  bath  after  each  operation  contains  3  to  4  per  cent, 
of  alcohol  and  is  discarded.  After  draining,  the  strips  are  kept  in  a  second  drier  for  some 
days,  until  the  percentage  of  solvent  (water,  alcohol  and  traces  of  ether),  is  reduced  to 
1-3  to  1-8,  and  are  finally  exposed  to  the  air  for  some  days  under  sheds,  thus  acquiring  a 
stable  composition,  which,  together  with  the  ballistic  effect,  remains  unchanged  even  after 
prolonged  storage. 

To  obtain  uniformity  in  powder  B,  strips  from  different  operations  are  well  mixed,  the 


298  ORGANIC    CHEMISTRY 

mass  being  translucent  and  of  a  pale  brownish-yellow  colour.  Before  being  despatched 
it  is  tested  by  the  ordinary  stability  tests. 

Waste  powder  B  is  utilised  by  softening  it  with  150  per  cent,  of  alcohol-ether  and  adding 
it,  little  by  little,  to  the  mass  in  the  kneading  machine. 

During  the  European  War,  the  Angouleme  works  in  France  produced  about  120,000 
kilos  of  the  powder  per  day,  the  alcohol  and  ether  consumed  amounting  to  some  dozens 
of  tons ;  the  Ferrania  factory  of  the  Societa  Italiana  Prodotti  Esplodenti  had  an  output 
of  15,000  kilos  per  day. 


Gelatine  Dynamites,  etc.  As  we  have  already  seen  in  dealing  with  the  theory  of  explo- 
sives, the  explosion  of  nitroglycerine  is  accompanied  by  the  liberation  of  unused  oxygen ; 
on  the  other  hand,  it  is  known  that  guncotton  does  not  contain  sufficient  oxygen  for  the 
complete  combustion  of  the  carbon  and  hydrogen  present  in  the  nitrocellulose  molecule. 

In  1875,  A.  Nobel  conceived  the  happy  idea  of  associating  the  two  substances  by  dis- 
solving in  nitroglycerine  a  certain  quantity  of  soluble  nitrocellulose,  that  is,  that  used  in 
the  manufacture  of  collodion.  This  procedure  gives  gelatines  of  varying  consistency  accord- 
•ing  to  the  quantity  of  nitrocellulose  (collodion-cotton)  dissolved.  Blasting  gelatine  is  made 
from  90  to  93  per  cent,  of  nitroglycerine  and  7  to  10  per  cent,  of  dry  collodion-cotton ;  gum 
dynamites,  on  the  other  hand,  contain  about  97  per  cent,  of  nitroglycerine  and  3  per  cent. 
of  collodion-cotton,  and  when  they  are  mixed  with  about  one-third  of  their  weight  of  absor- 
bent substances  (wood-meal,  rye-flour,  sodium  or  ammonium  nitrate)  they  form  the  ordinary 
modern  dynamites,  called  gelatine  dynamites,  which  are  still  plastic,  although  less  so  than 
the  gum  dynamites,  and  are  also  less  violent,  and  hence  serve  well  for  mining  purposes.  A 
common  type  of  gelatine  contains,  for  instance,  62-5  per  cent,  of  nitroglycerine,  2-5  per 
cent,  of  collodion-cotton,  25-5  per  cent,  of  sodium  nitrate,  8-75  per  cent,  of  wood-meal, 
and  0-75  per  cent,  of  sodium  carbonate  (which  would  be  best  excluded);  it  has  the  sp.  gr. 
1-5,  is  exploded  with  a  No.  3  fulminate  of  mercury  cap,  and  is  sold  in  Austria  for  No.  I 
dynamite,  whilst  gelignite  is  sold  for  No.  II  dynamite  and  contains  45  to  50  per  cent,  of  gum 
dynamite  and  about  50  per  cent,  of  absorbents  as  above. 

At  Christiania  a  non-congealing  gum  dynamite  is  made  from  blasting  gelatine  and  a 
little  nitrobenzene  and  ammonium  nitrate;  it  has  a  specific  gravity  of  1-49  and  is  less 
effective  than  the  gelatine  dynamites. 

For  military  purposes  (torpedoes,  cannon,  etc.),  as  much  as  4  per  cent,  of  camphor  is 
added  in  Italy,  Austria,  and  Switzerland ;  these  gelatines  are  thus  rendered  insensitive 
and  very  safe,  and  they  require  special  detonators  (e.  g.,  a  mixture  of  60  per  cent,  of 
nitroglycerine  and  40  per  cent,  of  collodion- cotton  or  compressed  guncotton). 

In  certain  commercial  products  the  collodion-cotton  is  replaced  by  nitrated  wood  or 
straw,  while  nitrobenzenes,  nitrotoluenes  (especially  liquid  dinitrotoluene ),  etc.,  are  used 
instead  of  nitroglycerine.1 

1  It  is  impossible  at  the  present  time  to  compare  the  various  commercial  brands  of  dynamite 
of  different  countries  or  even  of  one  country,  so  varied  are  the  types  and  the  ratios  of  the  com- 
ponents, sometimes  when  the  commercial  name  is  the  same.  Thus  No.  1  ammonia  dynamite 
(French)  contains  40  per  cent,  of  nitroglycerine,  45  per  cent,  of  ammonium  nitrate  (this,  when 
pure,  is  not  hygroscopic),  .5  per  cent,  of  sodium  nitrate,  and  10  per  cent,  of  wood-meal  or  wheat- 
flour;  the  No.  2  quality  of  the  same  brand  contains  20  per  cent,  of  nitroglycerine,  75  per  cent. 
of  ammonium  nitrate,  and  5  per  cent,  of  wood-meal.  In  Germany,  the  name  Gelatine  Dynamites 
is  given  to  all  mixtures  prepared  from  explosive  gum  (96  per  cent,  nitroglycerine  gelatinised  with 
4  per  cent,  collodion-cotton)  and  nitre  as  absorbent.  In  England,  however,  No.  2  gelatine  dyna- 
mites are  called  gelignites,  and  are  often  formed  of  65  per  cent,  of  the  gum  and  35  per  cent,  of 
absorbents  (75  per  cent,  nitre,  24  per  cent,  wood-meal — wood-pulp  used  for  paper,  in  a  dried 
state — and  1  per  cent,  of  soda).  In  Austria,  dynamite  I  is  made  from  65-5  per  cent,  of  nitro- 
glycerine, 2-1  per  cent,  of  collodion -cotton,  7-41  per  cent,  of  wood-meal,  24-85  per  cent,  of  nitre, 
and  0-26  per  cent,  of  soda ;  dynamite  II  contains  46  per  cent,  of  nitroglycerine,  etc.,  and  dynamite 
II  A,  38  per  cent,  of  nitroglycerine,  etc.  In  France,  gelatine  dynamites  are  called  gums,  and  are 
prepared  in  very  varied  forms,  e.  g.,  gum  M  B  with  74  per  cent,  of  nitroglycerine,  gum  D  with 
69-5  per  cent.,  and  gum  E  with  49  per  cent. ;  then  there  are  dynamite  gelatine  1,  2o,  26,  and  2c 
(the  last  with  43  per  cent,  of  nitroglycerine,  etc. ),  etc.  In  Belgium,  gelatine  dynamites  are  called 
forcites;  forcite  extra  contains  74  per  cent,  of  nitroglycerine,  superforcite  64  per  cent.,forcite  No.  2 
36  per  cent.,  etc. 

In  England  the  types  most  commonly  used  are  :   dynamite  No.  I,  with  75  per  cent,  of  nitro- 


GELATINE    DYNAMITES  299 

Gelatine  and  gum  dynamites  have  the  appearance  of  plastic  masses,  the  latter,  which 
has  the  sp.  gr.  1-6,  being  especially  horny  and  translucent.  Gum  dynamite  sometimes 
exudes  a  little  nitroglycerine  and  so  loses  in  shattering  force ;  when  heated  for  a  long  time 
at  70°,  it  swells  up,  becomes  spongy  and  decomposes  with  formation  of  red,  nitrous  vapours ; 
it  sometimes  ignites  in  metal  boxes  when  exposed  to  the  sun.  It  is  less  sensitive  even 
than  dynamite  (about  six  times  less)  to  percussion  and  special  caps  of  gelatine  dynamite  are 
required  to  explode  it.  It  serves  well  for  use  in  war,  since  it  is  insensitive  to  discharges, 
and  to  render  it  still  less  prone  to  detonation  by  influence  it  is  mixed  with  a  little  camphor. 
When  20  per  cent,  of  collodion-cotton  is  dissolved  in  nitroglycerine,  a  gum  dynamite  is 
obtained  which  is  not  exploded  by  the  most  powerful  caps,  and  ballistite,  which  contains 
30  to  50  per  cent,  of  collodion-cotton,  requires  special  detonators.  After  freezing  and 
thawing,  it  becomes  more  sensitive  and  dangerous,  as  is  the  case  with  dynamite.  It  has  a 
greater  shattering  power  than  dynamite  and  acts  better  than  this  under  water,  which  does 
not  wash  away  the  nitroglycerine  so  easily.  Exudation  of  nitroglycerine  occurs  more  readily 
than  with  dynamite  and  causes  some  degree  of  danger.  It  is  used  as  a  basis  for  the  manu- 
facture of  smokeless  powder.  Gelatine  dynamite  is  safer  to  handle  and  store  than  ordinary 
dynamite,  which  it  is  largely  replacing. 

The  manufacture  of  these  gelatinised  dynamites  requires  collodion-cotton,  which  is  very 
carefully  prepared  and  is  completely  soluble  in  a  mixture  of  alcohol  and  ether,  in  addition 
to  which  it  must  possess  as  great  a  proportion  of  nitrogen  as  possible.  When  it  is  not  well 
prepared,  although  it  dissolves  in  alcohol  and  ether,  it  is  not  readily  and  entirely  soluble 
in  nitroglycerine,  or  it  does  not  retain  the  latter  completely  for  a  long  time.  The  quality 
of  the  collodion-cotton  depends,  then,  on  the  choice  of  a  good  cotton  and  on  exact  conditions 
of  nitration — duration,  purity  of  acids,  temperature. 

This  should  then  be  finely  subdivided  (pulped)  and  dry,  so  that  it  can  be  passed  through 
a  fine  sieve  before  being  mixed  with  the  nitroglycerine,  in  which  it  does  not  dissolve  well 
if  moist.  This  operation  of  gelatinisation  and  kneading  is  termed  in  French  petrinage. 
The  necessary  quantity  of  nitroglycerine  is  placed  in  wide,  shallow  vessels  of  copper  or 
lead  heated  externally  by  hot  water  (50°  to  60°).  After  thirty  to  sixty  minutes,  when 
the  temperature  has  reached  45°  to  50°,  the  required  amount  of  dry,  powdered  collodion- 
cotton  (and  the  other  absorbent  substances  used  for  ordinary  dynamites,  such  as  cellulose, 
flour,  starch,  nitrate,  etc. ),  is  added  in  small  quantities  and  mixed  now  and  then  with  a 
wooden  spade.  It  is  then  left  for  a  couple  of  hours  and  afterwards  thoroughly  mixed  by 
hand,  just  as  dough  is  mixed,  so  as  to  form  a  homogeneous,  soft  paste ;  this,  on  cooling, 
forms  a  more  or  less  hard,  elastic,  translucent  gelatine  which  constitutes  the  gelatine  or 
explosive  gum.  If,  instead  of  collodion-cotton  alone,  absorbents  are  also  used,  gelatine 
dynamites  are  obtained ;  these  are  converted  into  rolls  and  cartridges  with  the  machines 
already  described  (p.  284).  When  the  gelatine  is  not  intended  for  the  manufacture  of 

glycerine ;  gelignite  with  65  per  cent,  of  gelatinised  nitroglycerine  (97  per  cent,  of  nitroglycerine), 
25  per  cent,  potassium  nitrate,  and  10  per  cent,  wood -meal;  blasting  gelatine  with  93  per  cent, 
of  nitroglycerine  and  7  per  cent,  of  collodion-cotton;  gelatine  dynamite  with  80  per  cent,  of  gela- 
tinised nitroglycerine  (with  3  per  cent,  of  collodion-cotton),  15  per  cent,  of  potassium  nitrate, 
and  5  per  cent,  of  wood-meal. 

In  Italy  there  is  dinamite-gomma  A  (or  simply  gomma  A,  corresponding  with  the  French  gomme 
extra-forte )  formed  from  92  per  cent,  of  nitroglycerine  and  8  per  cent,  of  collodion -cotton ;  gomma 
B  (corresponding  with  the  French  gomme  a  la  soude)  with  83  per  cent,  of  nitroglycerine,  5  per  cent, 
of  collodion-cotton,  8  per  cent,  of  sodium  nitrate,  3-7  per  cent,  of  wood-meal,  and  0-3  per  cent, 
of  sodium  or  calcium  carbonate  or  ochre.  Commercially,  however,  the  strength  is  given  in  terms 
not  of  nitroglycerine,  but  of  gelatine,  that  is,  the  starting  material  is  taken  as  a  gelatine  formed 
by  gelatinising  94  per  cent,  of  nitroglycerine  with  6  per  cent,  of  collodion-cotton,  to  which  are 
then  added  the  various  absorbents ;  thus  gomma  B  contains  88  per  cent,  of  gelatine  (equivalent 
to  83  per  cent,  of  nitroglycerine ).  In  Italy  the  old  kieselguhr  dynamite  is  no  longer  used  and  is 
replaced  by  the  so-called  gdatine-dinamiti,  which  are  marked  with  various  letters  and  numbers ; 
thus  No.  0,  containing  74  per  cent,  nitroglycerine,  5  per  cent,  collodion-cotton,  15-5  per  cent, 
sodium  nitrate,  5  per  cent,  wood-meal,  and  0-5  per  cent,  carbonates ;  G.  D.  No.  1,  with  70  to 
72  per  cent,  nitroglycerine,  etc. ;  G.  D.  No.  2,  with  about  48  per  cent,  nitroglycerine ;  and  dinamite 
No.  3,  with  25  per  cent,  nitroglycerine,  54  per  cent,  sodium  nitrate,  19  per  cent,  wood-meal  and 
cellulose,  and  2  per  cent,  soda  and  yellow  ochre.  During  recent  years  there  have  also  been  pre- 
pared in  Italy  gelatine-dinamiti — suggested  by  Dr.  Leroux — with  8  to  10  per  cent,  of  the  nitro- 
glycerine (of  No.  1 )  replaced  by  as  much  liquid  dinitrotoluene,  which  gelatinises  cotton  well  and 
gives  non -congealing  dynamites,  more  economical  and  almost  as  powerful  as,  sometimes  more 
powerful  than,  the  corresponding  gelatine'dynamites ;  these  act  well  in  open  mines,  but  give 
large  quantities  of  unpleasant  fumes,  and  hence  are  unsuitable  for  use  in  galleries,  etc. 


300 


ORGANIC    CHEMISTRY 


ballistite  (see  later),  the  conversion  into  cartridges  is  effected  by  means  of  an  Archimedean 
screw  machine  (boudineuse),  similar  to  sausage-making  machines  (Fig.  210). 

The  mixing  for  causing  gelatinisation,  especially  if  other  substances  besides  collodion- 
cotton  are  added,  may  be  carried  out  in  mechanical  kneading  machines  (Fig.  211)  mounted 
on  a  wooden  platform,  b,  which  can  be  raised  by  screws  and  cog-wheels,  g,  e,  and  h,  resting 
on  supports,  a  a ;  on  this  platform  is  a  double-walled,  copper  pan,  i  j,  which  can  be  sur- 
rounded with  hot  water  and  can  be  moved  on  rollers.  Above  are  the  bevel-wheels  and 

pulleys  for  working  the  stirrers,  q  and 
r.  The  nitroglycerine  is  first  heated 
to  50°  by  raising  the  temperature  of 
the  water  in  the  jacket  of  the  copper 
pan,  the  latter  being  then  raised  so 
as  to  submerge  the  stirrers  j  the ' 
ingredients  necessary  to  give  the 
required  type  of  gelatine  dynamite 
are  then  added.  Mixing  is  complete 
in  an  hour.  Other  forms  of  kneading 
machine  are  also  used,  e.  g.,  the 
FIG.  210.  Werner-Pfleiderer  machine,  which  is 

i  employed  for  smokeless  powders  and 

for  bread-making.  After  cooling,  the  plastic  dynamite,  which  has  a  yellowish,  translucent 
appearance,  is  removed  from  the  kneading  machine  to  a  separate  building  to  be  converted 
into  cartridges.  This  is  done  in  special  machines  (boudineuses)  (Fig.  212  and  213), 
furnished  with  endless  screws,  which  force  the  dynamite  or  gum  from  a  hole,  B,  in 
continuous  rolls,  these  being  collected  in  definite  lengths  in  a  casing  of  parchment  paper 
or  paraffin  waxed  paper,  (7. 

B.  Military  Smokeless  Powders.  These  approach  the  gum  dynamites  in  character, 
but  contain  more  collodion-cotton,  so  that  they  are  safer  towards  shock  and  useful  as 
propellants  (only  slightly  shattering). 

The  most  important  type  is  that  pre- 
pared by  Nobel  in  1888  under  the  name 
of  ballistite  (after  he  had  been  preparing 
since  1878  gum  dynamite  by  gelatinising 
nitroglycerine  with  6  to  10  per  cent,  of 
collodion- cotton).  Ballistite  contains 
about  50  jper  cent,  of  nitroglycerine  and 
50  per  cent.,  or  even  more,  of  collodion- 
cotton  (with  11-2  to  11-7  per  cent.  N). 
The  nitroglycerine  for  ballistite  should  be 
highly  stable  (for  at  least  twenty  minutes 
at  80°  by  the  Abel  test),  while  the 
collodion-cotton  should  have  a  stability 
of  twenty-five  minutes  at  71°  by  the 


Abel  test;  for  the  finished  ballistite  the 

stability  should  reach  thirty  minutes  at 

80°.     To  incorporate  these  two  substances 

thoroughly  and  so  that  there  is  no  danger 

in  the  subsequent  operations,  use  is  made 

of    Lundholm    and  Sayer's    process,    by 

which    the    constituents    are    united   in 

presence  of    a  liquid    able    to    dissolve 

neither  of  them.     This  liquid  is  merely 

water,  0-5  to  1  per  cent,  of  aniline  or  phenylamine,  or,  as  suggested  by  Spica,  phenanthrene, 

being  added  to  fix  the  nitrous  acids  liberated  and  thus  increase  the  stability  of  the 

ballistite. 

The  pulped  collodion-cotton,  containing  30  per  cent,  of  water,  as  it  comes  from  the  centri- 
fuges (after  stabilisation  with  15  parts  of  hot  water  per  1  part  of  nitrocotton)  is  introduced 
into  a  cylinder  of  sheet-lead  or  aluminium  containing  water  at  60°.  The  mass  is  well  stirred 
by  compressed  air  and  the  finely  divided  nitroglycerine  passed  in  by  means  of  a  compressed  - 


FIG.  211. 


301 


air  injector.  The  agitation  is  continued  until  all  the  nitroglycerine  is  incorporated  with 
the  cotton,  none  remaining  suspended  in  the  water.  The  whole  mass  in  then  discharged 
into  a  vessel  underneath  with  walls  and  bottom  of  fine  brass  gauze  or  silk.  When  it  has 
drained  well,  the  material  is  removed 
and  left  in  heaps  for  some  weeks  in 
order  that  the  gelatinisation  may  be 
completed.  The  further  treatment 
consists  of  coarse  sieving,  centrifuging 
to  remove  non-incorporated  water,  and 
a  first  rolling  between  two  rolls  almost 
touching  and  heated  to  about  50  to 
60°  by  means  of  internal  steam  (Fig. 
214 ).  It  is  thus  obtained  in  thick  non- 
homogeneous  leaves;  to  the  material 
used  to  form  these  leaves  are  added 
cuttings  and  waste  of  finished  ballis- 
tite,  which  is  first  softened  by  immer- 
sion for  some  hours  in  tepid  water. 
The  leaves  are  then  rolled  a  second 
time  between  rolls  which  are  more 
exactly  calibrated  and  adjustable  (see 
Fig.  214  a),  and  are  heated,  thinner 
sheets  of  definite  thickness  being  thus 
obtained.  All  extraneous  bodies 
(scraps  of  wood,  paper,  cotton,  etc.) 
are  removed  by  forceps  and  the  sheets 
are  examined  against  the  light  to  detect 
any  other  heterogeneous  particles. 

The  ballistite  is  then  cut  into 
strips  and  these  into  squares,  which 
are  seasoned  or  stabilised  by  spreading 
them  on  cloth  under  sheds  and  leaving 
them  for  two  or  three  weeks,  after 
which  the  material  undergoes  no 
further  change,  and  is  ready  to  be 
tested  and  stored. 

FIG.  213. 


FIG.  212. 


FIG.  214. 


FIG.  2 14  a. 


Ballistite  is  almost  brown  in  colour,  has  the  sp.  gr.  1-63  to  1-65,  and  is  practically 
unaffected  by  moisture;  it  inflames  at  180°  without  exploding.  The  gases  formed  in  its 
explosion  contain  no  nitrous  vapours  and  do  not  corrode  the  firearms  to  any  extent.  Such 


302  ORGANIC    CHEMISTRY 

corrosion  is  caused  especially  by  the  very  high  temperature  produced  by  the  explosion  of 
the  ballistite  and  by  the  friction  of  the  hot  gases. 

With  lapse  of  time  a  very  small  part  of  the  nitroglycerine  appears  to  evaporate,  the 
strength  and  properties  of  the  ballistite  being  thereby  modified.  For  this  reason  ballistite 
is  replaced  to  some  extent  by  solenite  and  cordite,  which  contain  less  nitroglycerine.1 

With  some  smokeless  powders,  attempts  have  been  made  to  replace  the  nitrocellulose 
by  nitrated  starch  and  the  liquid  solvents  by  the  corresponding  vapours,  but  no  advantage 
has  yet  been  procured  in  this  way.  Explosive  gelatines  may  also  be  obtained  by  adding 
metallic  nitrates  (of  barium  or  potassium )  to  the  collodion-cotton ;  these  have  diminished 
power  but  possess  the  advantage  of  being  readily  inflammable.  Mixtures  of  collodion- 
cotton  and  nitropentaerythritol  have  recently  been  prepared  for  the  use  of  large-bore 
artillery. 

PROPERTIES  OF  SMOKELESS  POWDERS.  Those  formed  of  nitro- 
cellulose alone  are  hard ;  ballistite  is  not  so  hard,  and  even  in  thick  strips  can 
be  bent  and  then  broken  like  a  very  hard  paste.  They  are  very  resistant  to 
the  action  of  water  and  so  have  a  great  advantage  over  ordinary  black  powders, 
which  are  destroyed  by  water.  They  also  possess  the  advantages  of  a  high 
density,  1*6  or  more  (see  p.  262). 

The  velocity  imparted  to  the  projectile  increases  with  the  percentage  of 
nitrogen  in  the  smokeless  powder ;  for  one  and  the  same  velocity,  the  explosive 
which  develops  the  lowest  pressure  causes  the  least  wear  of  the  barrel  and  is 
also  the  most  safe. 

Whilst  Vieille's  smokeless  powder  (gelatine  of  pure  guncotton)  withstands 
all  ordinary  conditions  of  temperature  and  moisture,  ballistite,  on  the  other 
hand,  gradually  loses  nitroglycerine  and  so  undergoes  change  of  its  properties 
if  the  humidity  of  the  atmosphere  oscillates  much.  These  conditions  are, 
however,  rarely  met  with  in  practice,  and  ballistite  is  used  not  only  by  the 
Italian  army  and  navy,  but  also  by  other  Governments,  and  is  in  some  ways 
superior  to  the  cordite  used  in  the  British  and  also,  to  a  certain  extent,  in  the 
Italian  armies.  In  1906,  the  proportions  of  the  components  of  cordite  were 
varied  slightly  and  the  form  altered  to  that  of  ribbons,  being  then  known  as 
axite.  Smokeless  powders  withstand  the  blow  of  a  projectile  and  require  special 
detonators,  fulminate  of  mercury  not  giving  good  results.  They  are  exploded 
by  compressed  guncotton  caps,  which  in  their  turn  are  exploded  by  fulminate 
of  mercury. 

If  accidentally  ignited,  smokeless  powders  are  not  very  dangerous,  since 
they  do  not  explode,  but  regard  must  be  paid  to  the  very  high  temperatures 
(above  3000°)  produced,  as  these  will  melt  iron,  stone,  etc. 

1  Cordite,  prepared  by  Abel  in  1889,  is  a  smokeless  powder  in  filaments  like  hollow  twine. 
Modern  cordites  contain  65  per  cent,  of  .guncotton  (not  collodion-cotton),  30  per  cent,  of  nitro- 
glycerine, and  sometimes  5  per  cent,  of  vaseline.  Guncotton,  which  is  insoluble  (to  the  extent 
of  90  per  cent. )  in  alcohol,  ether,  or  even  nitroglycerine,  may  also  be  gelatinised  by  the  action 
of  a  common  solvent,  e.  g.,  acetone,  which  gives  a  colloidal  solution  persisting  even  after  evapora- 
tion of  the  solvent.  The  dry  guncotton  is  first  mixed  by  hand  with  nitroglycerine,  the  mass  being 
then  introduced  into  an  ordinary  kneading  machine,  which  is  of  bronze  and  is  jacketed  to  allow 
of  water-cooling ;  the  acetone  (20  kilos  per  100  kilos  of  the  paste )  is  then  added  and  kneading 
continued  for  at  least  3  hours,  after  which  the  vaseline  is  mixed  in  for  some  time.  The  mass  tends 
to  heat'and  must  be  cooled.  At  the  end  of  the  operation,  lumps  of  the  paste,  roughly  cylindrical 
in  form,  are  introduced  into  the  cylinder  of  the  cordite  press,  which  is  similar  to  that  used  for 
making  macaroni.  The  threads  of  varying  thickness,  length,  and  shape  of  cross-section  thus 
obtained  are  then  dried  at  40°  for  five  to  eight  days,  and  afterwards  left  for  three  or  four  weeks 
in  the  air  to  undergo  stabilisation. 

Solenite,  prepared  in  a  similar  manner  in  thin  threads,  is  used  in  Italy  as  a  rifle  powder,  and 
consists  of  36  per  cent  of  nitroglycerine,  61  per  cent,  of  nitrocellulose  (one-half  guncotton  and 
one-half  collodion-cotton),  and  about  3  per  cent,  of  mineral  oil. 

Powder  C2,  made  in  England  by  Messrs.  Chilworth  and  also,  since  1910,  by  the  Nobel  Dyna- 
mite Company  of  Avigliana,  resembles  cordite,  and  consists  of  70'5  per  cent,  of  nitrocellulose 
(two-thirds  collodion,  one-third  guncotton),  23'5  per  cent,  of  nitroglycerine,  5  per  cent,  of  va&eline, 
and  1  per  cent,  of  sodium  bicarbonate;  gelatinisation  is  facilitated  by  the  use  of  acetone. 


PICRIC    ACID  303 

SMOKELESS  AND  FLAMELESS  EXPLOSIVES.  From  a  military  point  of  view, 
a  great  advance  was  made  by  the  replacement  of  black  powder  by  smokeless  powders,  since 
the  latter  do  not  obscure  the  artilleryman's  view  and  also  render  difficult  the  exact  location 
of  the  battery  by  the  enemy.  It  still  remained  possible,  however,  especially  at  night-time 
and  with  large  guns,  to  determine  the  position  of  these,  since,  as  the  projectile  leaves  the 
muzzle,  the  hot  gases  resulting  from  the  explosion  extend  into  the  air,  producing  flames 
50  cm.  or  even  a  metre  in  length.  A  few  years  prior  to  the  European  War  successful 
attempts  were  made  in  various  countries  (Germany,  Roumania,  etc.)  to  eliminate  these 
flames  almost  completely  by  addition  to  the  explosive  of  certain  substances,  especially 
small  proportions  of  diphenylamine,  diphenyldimethylurea,  neutral  ammonium  oxalate, 
etc.  Herein  probably  lies  the  reason  why  the  big  German  guns  were  able  to  fire  on 
Dunkirk  and  Paris  from  a  distance  of  a  hundred  kilometres  without  discovery. 

Analogous  results  are  obtained  with  the  so-called  safety  mine  explosives  (see  p.  305). 

In  1906  Duttenhofer  patented  the  addition  of  potassium  bicarbonate  to  smokeless 
powders  to  diminish  the  flame,  but  the  results  thus  yielded  are  not  highly  satisfactory. 

Stabilisers  for  smokeless  powders  and  dynamites.  To  render  these  explosives  physically 
more  stable,  that  is,  less  sensitive  to  shock,  it  is  sufficient  to  mix  intimately  with  them 
paraffin  wax,  vaseline,  camphor  (see  celluloid),  mineral  oil,  castor  oil,  etc.,  in  more  or  less 
large  proportions  (1  to  10  per  cent. ). 

To  stabilise  explosives  chemically  by  retarding  or  preventing  their  spontaneous  decom- 
position, various  additions  are  made.  Thus,  after  the  first  cases  of  such  decomposition 
with  powder  B,  Vieille  suggested  the  addition  of  a  little  amyl  alcohol  (2-4  per  cent. ),  which 
doubled  the  stability;  in  1896  it  was  found  that  a  far  higher  stability  still  was  effected  by 
2  per  cent,  of  diphenylamine.  Aniline,  which  acts  similarly  but  less  efficaciously,  has  long 
been  added  to  ballistite.  The  last  stabilisers  have  the  property  of  fixing  any  traces  of 
nitrous  acid  formed  during  the  slow  decomposition  of  the  powder,  thus  preventing  rise  of 
te'mperature  and  slackening  the  decomposition.  These  substances  are,  of  course,  sometimes 
used  to  mask  incipient  decomposition  at  the  time  the  explosives  are  to  be  examined. 

Of  the  numerous  other  stabilisers  suggested,  the  following,  which  have  given  good 
results,  may  be  mentioned  :  ammonium  and  sodium  ammonium  oxalates,  urea,  nitro- 
guanidine  and  mercuric  chloride  (this  only  masks  the  reactions  by  which  the  stability  is 
controlled). 

SHATTERING   EXPLOSIVES 
AROMATIC   NITRO-DERIVATIVES  :   PICRATES 

PICRIC  ACID  (melinite,  shimose,  lyddite,  pertite).  As  early  as  the  fifteenth 
century  an  alchemist  obtained  an  explosive  substance  by  treating  a  kind  of 
tar  with  aqua  regia,  but  this  acquired  no  importance  in  comparison  with  ordinary 
gunpowder.  The  explosive  properties  of  picric  acid,  CGH2(NO2)3OH,  and  its  salts  were 
studied  in  the  second  half  of  the  nineteenth  century  and  assumed  considerable  importance 
when,  in  1886,  Turpin  prepared  melinite  from  70  per  cent,  of  picric  acid  and  30  per  cent,  of 
collodion-cotton  previously  rendered  soluble  with  alcohol  and  ether;  this  was  regularly 
used  for  some  years  by  the  French  army  in  place  of  dynamite.  At  the  present  time  fused 
picric  acid  (m.-pt.  122°;  sp.  gr.  1-64-1-66)  is  poured  into  cartridges  containing  a  fulminate 
of  mercury  cap  and  powdered  picric  acid.  The  manufacture  of  picrc  acid  from  carbolic 
acid,  and  also  its  properties,  are  described  in  Part  III  (chapter  in  Aromatic  Nitro- 
derivatives). 

Weight  for  weight,  picric  acid  is  less  effective  than  dynamite,  but,  measured  by  volume, 
its  power  is  greater  than  that  of  dynamite,  the  specific  gravity  of  which  is  1-5.  It  has  also 
the  advantage  over  dynamite  in  that  it  does  not  freeze,  being  already  in  the  solid  state. 

In  England,  melinite  was  followed  in  1888  by  lyddite,  containing  about  87  per  cent,  of 
picric  acid,  10  per  cent,  of  nitrobenzene,  and  3  per  cent,  of  vaseline.  This  is  poured  in  a 
molten  state  into  the  cartridges  and  is  exploded  with  ammonium  picrate  detonators ;  it  is 
highly  resistant  to  shock.  It  undergoes  decomposition  fairly  readily,  giving  poisonous  gases, 
containing  about  61  per  cent,  of  carbon  monoxide  and  13  per  cent,  of  carbon  dioxide.  For 
this  reason  picric  acid  and  all  similar  compounds  cannot  be  used  in  the  galleries  of  mines. 
The  ease  with  which  picrates  form  in  contact  with  iron,  lime  etc.,  has  led  to  many  disasters, 
since  picrates  are  readily  exploded  by  shock.  The  insides  of  bombs  and  projectiles  to  be 
charged  with  picric  acid  are  varnished,  as  also  are  the  capsules  fcr  the  caps.  Fusion  of 


304  ORGANIC    CHEMISTRY 

picric  acid  is  carried  out  in  aluminium  vessels;  at  a  temperature  somewhat  above  the 
melting-point,  picric  acid  is  highly  sensitive  and  dangerous. 

During  the  European  War,  in  order  to  increase  the  quantity  of  explosive  with  a  basis 
of  picric  acid,  use  was  made  on  an  enormous  scale  of  a  fused  mixture  of  60  per  cent,  of 
picric  acid  and  40  per  cent,  of  dinitrophenol  (m.-pt.  111-5°;  for  preparation,  see  Part  III). 
This  has  explosive  powers  almost  equal  to  those  of  picric  acid,  and  is  more  stable  and  less 
dangerous  to  handle,  while  it  has  the  great  advantage  that  its  melting-point  is  below  90°, 
that  of  picric  acid  being  122°.  Further,  for  this  mixture  use  may  be  made  of  moist  picric 
acid,  since  the  water  separates  completely  and  floats  on  the  mass  during  the  fusion ;  the 
danger  involved  in  drying  the  picric  acid  is  thus  avoided. 

TRINITROTOLUENE.  Some  years  before  the  European  War  picric  acid  had  been 
replaced  in  Germany,  Italy  and,  partly,  in  England  by  trinitrotoluene,  which  melts  at 
80-5°  and  has  the  same  power,  but  is  more  stable  and  less  dangerous  to  make  and  to  handle ; 
further,  it  does  not  combine  with  metals.  Part  III  contains  a  description  of  the  properties 
and  manufacture  of  this  product,  which  was  used  during  the  war  on  a  vast  scale  by  all 
the  belligerents. 

Another  explosive  which  was  largely  used  in  the  war  and  is  cheap,  easily  prepared,  safe 
to  handle,  and  moderately  powerful,  consists  of  an  intimate  mixture  of  12  per  cent,  of 
dinitronaphthalene  (a  mixture  of  various  isomerides,  see  Part  III)  and  88  per  cent,  of 
ammonium  nitrate;  the  mixture  was  compressed,  but  not  excessively,  in  the  projectile. 
This  product  (and  others  similar)  was  patented  in  1885  by  Favier  and  in  France,  during 
the  war,  bore  the  name  schneiderite,  being  made  at  the  Creusot  works  of  Messrs.  Schneider ; 
in  Italy  it  was  made  by  the  Societa  Italiana  Prodotti  Esplodenti  (S.I.P.E.)  of  Cengio  and 
was  termed  siperite. 

Various  other  mixtures  with  bases  of  atomatic  nitro-derivatives  (nitrocresols,  etc. )  were 
used  during  the  war. 

SPRENGEL  EXPLOSIVES.  In  1871  H.  Sprengel,  starting  from  the  fact  that  explosion 
is  nothing  but  instantaneous  combustion,  conceived  the  idea  of  preparing  explosives  by 
mixing  a  readily  combustible  substance  with  one  possessing  considerable  oxidising  pro- 
perties; the  substances  separately  are  not  explosive,  but  become  so  when  mixed,  mixing 
taking  place  only  at  the  spot  where  the  explosive  is  to  be  used. 

In  January  1871,  a  few  months  before  Sprengel's  discovery,  Silas  R.  Devine  had  prepared 
and  used  a  mixture  of  potassium  chlorate  and  nitrobenzene,  but  he  kept  the  process  secret ; 
in  1880  he  prepared  rackarock  powder,  formed  by  mixing  the  potassium  chlorate  and 
nitrobenzene  just  before  use  (see  below). 

This  idea  was  taken  up  later  by  Hellhoff,  who  mixed  nitric  acid  with  nitrated  hydro- 
carbons, and  more  effectually  by  Turpin  and  by  R.  Pictet,  who  mixed  nitrogen  peroxide 
(N204)  with  various  nitrated  organic  compounds  and  also  with  CS2  (pandastite,  fulgurite, 
etc.),  but  these  explosives  never  came  into  practical  use. 

Another  form  of  explosive  of  the  Sprengel  type  is  that  with  ammonium  nitrate  as  base ; 
this  has  been  largely  used  during  recent  years  and  is  five  or  six  times  as  powerful  as 
gunpowder. 

The  most  important  of  these  explosives  is  Favier  powder  (1885),  which,  in  its  different 
forms,  usually  consists  of  a  mixture  of  ammonium  nitrate  and  nitronaphthalenes,  and 
sometimes  contains  also  sodium  nitrate,  aluminium,  etc.  (see  later :  Prometheus  Powder). 

CHLORATE  AND   PERCHLORATE   POWDERS 
(Partly  of  the  Sprengel  type) 

CUorate  powders,  first  proposed  by  Berthollet  in  1785  to  obtain  greater  power,  and 
containing  potassium  chlorate  instead  of  nitre,  have  not  been  very  successful,  and  even 
when  a  part  of  the  nitre  is  restored,  accidental  explosions  often  occur,  owing  to  the  great 
sensitiveness  to  shock.  In  America,  Devine  (1881)  retains  the  potassium  chlorate,  but 
keeps  the  ingredients  of  the  powder  separate  until  required  (as  is  done  with  the  Sprengel 
explosives  (see.  above);  thus  rackarock  for  blasting  contains  79  per  cent,  of  potassium 
chlorate  and  21  per  cent,  of  nitrobenzene  (liquid),  mixed  sometimes  with  picric  acid,  sulphur, 
etc.  These  powders  are  rendered  less  sensitive  to  shock  by  mixing  with  a  little  wax  (e.  g. 
Brank's  powder).  In  1896,  at  St.  Petersburg,  Jevler  prepared  promelheus  from  a  solid 
portion  (90  per  cent,  potassium  chlorate  +  10  per  cent,  of  manganese  dioxide  +  a  little 


SAFETY    EXPLOSIVES  305 

ferric  oxide),  and  a  liquid  portion  (55  per  cent,  of  mononitro benzene  +  18  per  cent,  of 
turpentine  oil  +  27  per  cent,  of  naphtha ) ;  a  factory  for  this  explosive  was  erected  in  Italy 
in  1905,  but  it  was  destroyed  by  a  terrific  explosion  in  1909,  ten  persons  being  wounded 
and  five  killed.  In  1901  donnar  was  placed  on  the  market;  it  contains  56  per  cent,  of 
chlorate  and  24  per  cent,  of  potassium  permanganate  for  the  solid  part,  and  16  per  cent, 
of  nitrobenzene  and  4  per  cent,  of  turpentine  for  the  liquid  part.  Also  nitronaphthalene 
and  castor  oil  (5  to  8  per  cent.)  are  used  to  render  the  mixture  more  stable,  e.  g.,  with 
cheddite  and  with  pierrite  :  80  per  cent,  of  chlorate  +  12  per  cent,  nitronaphthalene  +  6  per 
cent,  castor  oil  +  2  per  cent,  picric  acid  (or,  better,  2  per  cent,  dinitrotoluene ),  the  whole 
being  well  mixed ;  this  powder  has  double  the  power  of  ordinary  blasting  powder. 

To  replace  dynamite,  miedziankite,  consisting  of  90  per  cent,  of  chlorate  and  10  per  cent, 
of  petroleum,  has  been  suggested  (1912). 

More  advantageous  still  are  thought  to  be  the  potassium  perchlorate  powders  (Nisser 
powder,  1865,  contains:  perchlorate,  10-5;  nitrate,  44-5;  bichromate,  2;  ferrocyanide, 
1-5;  sulphur,  15-5;  charcoal,  19-5;  and  vegetable  substances,  6-5  per  cent. ).  Better  still 
are  those  containing  ammonium  perchlorate,  recently  invented  by  U.  Alvisi  (manlianite  : 
72  per  cent,  perchlorate,  14-75  charcoal,  13-25  sulphur;  Cannel  powder :  80  per  cent,  of 
perchlorate,  and  20  per  cent,  of  cannel  coal ;  cremonite,  with  48-85  per  cent,  of  ammonium 
perchlorate,  and  51-15  per  cent,  of  ammonium  picrate ;  and  the  kratites  obtained  by  mixing 
perchlorates  with  nitroglycerine  and  with  nitrocellulose).  Perchlorate  powders  should  be 
used  cautiously,  and  to  render  them  less  sensitive  without  imparing  their  great  shattering 
power,  they  are  mixed  with  urea,  guanidine,  dicyanodiamidine,  etc. ;  if  nitrate  is  added, 
the  chlorine  is  partly  fixed,  and  the  explosions  then  obtained  are  especially  suited  to  mines 
with  thin  and  extended  seams.  Hydrogen  chloride  also  is  formed  to  some  extent  in  the 
explosion  ;  2NH4C104  =  2HC1  +  2N  +  3H20  +  5O,  the  theoretical  temperature  of  the 
explosion  being  1084°  and  the  volume  of  gas  liberated  1615  litres  of  gas  per  kilo  of  the 
explosive. 

In  1905  a  patent  was  taken  out  for  a  powder  containing  47  per  cent,  of  ammonium 
nitrate,  1  per  cent,  of  charcoal,  30  per  cent,  of  orthonitrotoluene,  and  20  per  cent,  of  very 
finely  powdered  aluminium,  the  whole  being  compressed  under  a  pressure  of  5000  kilos 
per  square  centimetre,  and  then  moistened  with  nitrotoluene  in  a  water-bath  at  67°. 

SAFETY  EXPLOSIVES  (for  Mines  Rich  in  Firedamp).1  Firedamp  (see  p.  34)  is  a 
mixture  of  methane  and  air  and  is  formed  particularly  in  coal-mines.  It  burns  at  450° 
and  inflames  at  650° ;  in  presence  of  spongy  platinum  it  burns  even  at  200°.  For  ignition 
to  occur,  a  certain  time— at  least  some  seconds — is  necessary.  For  instance,  at  650°  about 
10  seconds  elapses  before  the  explosive  mixture  ignites,  whilst  at  1000°  ignition  occurs  in 
1  second.  This  explains  why,  for  example,  the  gases  produced  at  a  temperature  of  2000° 
by  shattering  explosives  do  not  always  fire  the  explosive  mixture,  the  explosion  occurring 
with  enormous  rapidity  (scarcely  measurable).  The  danger  of  ignition  is  diminished  by 
decrease  of  the  quantity  of  gas  formed,  i.  e.,  of  explosive  used  for  each  charge;  the  very 
hot  gases  produced  expand  rapidly  and  become  cooled,  so  that  they  are  unable  to  cause 
ignition  of  the  firedamp.  Further,  if  the  heat  of  the  gases  is  efficiently  utilised  to  give  the 

1  The  frequent  explosions  occurring  in  mines  have  led  scientific  men  to  make'  attempts 
to  mitigate  their  effects  and  to  render  them  less  common.  In  the  tremendous  explosion 
of  March  10,  1906,  in  the  Courriere  mines  (France)  there  were  1000  victims,  600  being 
killed ;  thirteen  workmen  were  rescued  alive  after  twenty  days.  Commissions  have  been 
appointed  in  France  (1880),  Russia  (1887),  Austria  (1891),  and  other  countries.  In  England 
the  question  has  been  studied  by  Macnab  (1876)  and  Abel  (1886);  in  France  by  Mallard  and  Lo 
Chatelier  (1883),  Watteyne,  etc.;  in  Germany  by  Winckhaus  (1895),  very  systematically  by 
C.  E.  Bichel  and  Mettegang  (1904-1907),  who  devised  various  ingenious  forms  of  indicating 
apparatus,  Beyling  (1903-1907)  and  Heise  (1898);  and  in  Austria  by  Siersch  (1896),  Bohm  (1886), 
Mayer  (1889),  and  Hess  (1900). 

The  studies  of  Bichel  more  especially  have  shown  that  the  safety  of  an  explosive  for  use  in 
mines  (especially  coal-mines)  depends  simultaneously  on  several  factors,  each  of  which  must  lie 
within  definite  limits,  excess  of  one  of  these  not  being  able  to  compensate  for  deficiency  of  another. 
Thus,  for  example,  ordinary  black  powder,  which  has  almost  all  the  requisites  of  a  safety  explosive, 
cannot  be  employed,  for  the  sole  reason  that  the  duration  of  its  flame  is  too  long  and  so  renders  it 
dangerous.  The  principal  factors  establishing  the  safety  of  an  explosive  are  :  velocity  of  explo- 
sion, temperature  of  the  gases  formed,  length  of  the  flame,  duration  of  the  flame,  and  quantity 
of  explosive  used  in  each  explosion.  The  results  of  experiments  made  in  England  and  America 
up  to  1913  show  that  the  safety  of  mine  explosives  is  influenced  also  by  the  diameter  of  the 
cartridge,  the  density  of  the  charge,  the  granulation,  the  tamping,  and  the  degree  of  moistness 
of  the  air. 

VOL.  ii.  20 


306  ORGANIC    CHEMISTRY 

maximum  amount  of  mechanical  work  (splitting  of  the  rock),  the  risk  of  firing  is  diminished ; 
hence  follows  the  necessity  of  a  good  tamping  for  each  charge  in  order  that  the  escape  of 
the  gases  without  performing  work  may  be  prevented. 

Explosion  in  the  open  is  more  likely  to  ignite  firedamp.  In  mines  the  use  of  a  powerful 
detonator  is  advantageous,  in  order  that  the  explosion  may  be  sharp  and  rapid.  Mine 
explosives  should  contain  sufficient  oxygen  to  produce  only  C02  and  not  the  poisonous  CO. 

Instead  of  calculating  the  temperature  and  duration  of  explosion,  it  is  preferable  in 
practice  to  make  direct  experiments  with  small  cannons  placed  against  a  rock  at  the  bottom 
of  a  long,  wide  iron  tube  or  test-chamber  (20  cu.  metres),  containing  an  explosive  gas.  Dis- 
charge of  the  cannons  should  not  ignite  the  gas  if  the  explosive  is  safe.  In  France  it  is 
prescribed  by  law  that  in  mines  explosives  'must  be  used  which  give  gases  of  maximum 
degree  of  oxidation  but  no  inflammable  gas  (CO,  H2)  or  solid  carbide  :  further,  the  tempera- 
ture of  detonation,  calculated  according  to  a  formula  of  Mallard  and  Le  Chatelier,  must  not 
exceed  1500°  (or  for  certain  piercing  operations,  1900°). 

Gunpowder,  dynamite,  and  blasting  gelatine  readily  cause  explosion  of  firedamp  in 
mines,  their  temperatures  of  explosion  exceeding  2200°  (as  shown  by  Mallard  and  Le 
Chatelier).1  In  order  to  meet  the  requirements  of  a  safety  explosive,  various  ingenious 
processes  are  employed  to  lower  the  temperature  of  the  gases  from  the  explosion  sufficiently 
to  prevent  them  giving  a  flame.  The  charges  are  wrapped  up  and  the  tamping  made  with 
water  or  with  gelatine  containing  98  per  cent,  of  water  (or  with  special  sponges  saturated 
with  water,  etc.).  Salts  containing  much  water  of  crystallisation  have  also  been  used 
for  tamping,  but  without  good  results,  the  tamping  being  simply  projected  to  a  distance 
without  evaporation  of  the  water.  A  safer  plan  consists  in  mixing  the  explosive  directly 
with  such  salts,  the  water  of  crystallisation  then  evaporating  with  considerable  absorption 
of  heat,  at  the  instant  of  explosion.  Finally,  use  is  made  of  explosives  with  ammonium 
nitrate  as  base,  the  temperature  of  explosion  of  the  nitrate  being  only  1130°  and  the  reaction 
occurring  thus  :  NH4N03  =  N2  +  2H20  +  0.  Since,  however,  the  explosive  effect  of 
ammonium  nitrate  is  small,  it  is  combined  with  other  substances,  e.  g.,  with  dynamite  or 
with  Favier's  explosive.  In  some  cases,  in  addition  to  the  nitrate,  ammonium  chloride  is 
used,  this  undergoing  dissociation  with  absorption  of  heat  from  the  gases. 

To  lower  the  temperature  of  the  flame,  and  especially  to  obtain  smokeless  and  flameless 

1  Dynamite  and  especially  gunpowder,  if  exploded  without  tamping,  will  certainly  ignite 
firedamp  or  even  the  coal-dust  suspended  in  the  air  of  coal-mines.  The  dangeris  diminished,  but 
not  excluded,  by  tamping,  so  that  even  in  1853  the  Englishman  Elliot  suggested  replacing  the 
explosives  by  quicklime,  a  large  compressed  charge  of  which  is  placed  in  a  cavity  in  the  rock; 
the  pipe  from  a  pressure  water-pump  is  then  introduced  and  a  good  tarnping  effected.  The  water, 
coming  into  contact  with  the  lime,  increases  the  volume  of  the  latter  two  to  five  times,  and,  with 
the  steam  formed  at  the  same  time,  pressures  of  500  atmos.  can  be  obtained.  In  1880  the  use  of 
lime  cartridges  was  fairly  general  in  mines,  but  they  were  abandoned  later  owing  to  the  unsatis- 
factory results  given.  No  better  fortune  befell  cartridges  of  quicklime,  water,  and  sulphuric 
acid,  or  powdered  aluminium  and  sulphuric  acid  (which  develop  hydrogen),  or  chlorine  and 
ammonia  compressed  separately  and  then  united,  or  compressed  explosive  mixtures  of  oxygen 
and  hydrogen.  In  1876,  Macnab  suggested  tamping  gunpowder  charges  with  water,  but  this  did 
not  always  prevent  explosion  of  the  firedamp ;  the  same  system  applied  to  dynamite  by  Abel  in 
1886  gave  better  results.  In  some  cases,  the  water  is  replaced  by  moist  substances  (sand,  moss, 
etc. ),  which  yield  good  results. 

In  mines  which  give  much  coal-dust  there  is  the  greatest  danger  of  disaster  when  large  charges 
(of  more  than  100  to  150  grams)  are  used,  and  when  the  coal  contains  22  to  35  per  cent,  of  Volatile 
products. 

Although  firedamp  ignites  at  650°,  explosives  can  be  used  which  have  a  temperature  of 
explosion  only  slightly  below  2200°  (roburite,  1616°;  westphalite,  1806°;  carbonites  for  coal- 
mines, 1820°  to  1870°,  etc. ),  since  the  gases  cool  on  expanding.  Even  these  explosives  are,  how- 
ever, dangerous  if  the  charges  are  large  (above  300  grams  for  roburite  and  westphalite,  and  above 
1000  grams  for  the  carbonites),  since  then  a  momentary  pressure  on  the  air  is  developed  (especially 
if  the  velocity  of  explosion  is  high)  and  a  decided  rise  of  temperature.  Explosives  which,  in 
charges  of  600  to  800  grams,  do  not  ignite  the  explosive  mixture  in  the  test-chamber,  may  be 
safely  used  in  fiery  mines. 

The  length  and  duration  of  the  flame  of  the  explosion  are,  however,  of  the  greatest  importance, 
and  ordinary  black  powder  is,  as  stated  above,  very  dangerous  in  such  mines  owing  solely  to  the 
marked  duration  and  length  of  the  flame.  More  dangerous  still  are  those  explosives  which  cause 
considerable  dilatation  of  the  leaden  blocks  (see  later,  Fig.  230,  p.  317),  and  those  which  give, 
among  their  products  of  explosion,  carbon  monoxide  and  hydrogen,  but  not  oxygen,  since  these 
gases  on  burning  (rapidly)  withdraw  oxygen  from  the  flame  of  the  explosive  and  almost  stifle  it. 
A  good  safety  explosive  ceases  to  be  such  if  it  is  not  always  prepared  with  the  same  care  and  of 
equal  uniformity  from  the  same  materials. 


FLAMELESS    EXPLOSIVES 


307 


powders,  addition  of  nitrodicyanodiamidine  or  dicyanodiamide  (see  Vol.  I.,  p.  371)  has 
been  tried  with  success.  Use  has  also  been  made  of  vaseline,  oil  of  paraffin,  camphor  or 
2  to  5  per  cent,  of  sodium  oxalate,  tartrate,  or  citrate  (Ger.  Pat.  243,846). 

Various  kinds  of  such  explosives  give  good  results,  e.  g.,  grisounite,  containing  44  per 
cent,  nitroglycerine,  12  per  cent,  nitrocellulose,  and  44  per  cent,  crystallised  magnesium 
sulphate  (MgSO4  -f  7H2O);  also  roburite,  with  82  per  cent,  of  ammonium  nitrate  and  18 
per  cent,  of  dinitrobenzene ;  Nobel's  wetter-dynamite,  with  53  per  cent,  nitroglycerine,  14-3 
per  cent,  kieselguhr,  and  32-7  per  cent,  magnesium  sulphate;  securite,  with  37  per  cent, 
ammonium  nitrate,  34  per  cent,  potassium  nitrate,  and  29  per  cent,  nitrobenzene ;  westphalite, 


FIG.  215. 
100  grams  of  Gelatine  Dynamite 


FIG.  216. 
100  grams  of  Dynamite  (Kieselguhr) 


FIG.  217. 
100  grams  Roburite 


FIG.  218. 
100  grams  Carbonite 


FIG.  219. 
100  grams  Grisounite 


containing  94  per  cent,  ammonium  nitrate,  and  6  per  cent,  resin ;  carbonite,  with  25  per  cent, 
nitroglycerine,  40  per  cent,  wood-meal,  30-5  per  cent,  potassium  nitrate,  4  per  cent,  barium 
nitrate,  and  0-5  per  cent,  sodium  carbonate ;  ammoncarbonile  contains  82  per  cent,  of 
ammonium  nitrate,  10  per  cent,  of  potassium  nitrate,  4  per  cent,  of  nitroglycerine,  and 
4  per  cent,  of  wheat  flour;  vigorite,  containing  30  per  cent,  nitroglycerine,  49  per  cent, 
potassium  chlorate,  7  per  cent,  potassium  nitrate,  9  per  cent,  wood-pulp,  and  5  per  cent, 
magnesium  carbonate.  Even  these  substances  are  not,  however,  safe  in  the  absolute 
sense  of  the  word;  with  such  additions  of  inert  products,  the  explosives  lose  in  force  but 
gain  in  safety. 

In  1896  Schoneweg,  and  then  Siersch,  starting  from  the  hypothesis  that  the  smaller  the 


308  ORGANIC    CHEMISTRY 

flame  produced  in  an  explosion,  the  safer  will  be  the  explosive,  photographed,  on  dark 
nights,  the  flames  produced  by  the  free  explosion  of  100-gram  cartridges.  As  will  be  seen 
from  Figs.  215  to  220,  these  flames  are  of  value,  although  they  are 
not  absolutely  decisive,  since  the  non-luminous  (ultra-violet)  rays 
also  act  on  the  photographic  plate.  In  Fig.  215  is  seen  a  small 
luminous  spot  detached  from  the  principal  flame,  this  being  due 
either  to  the  surrounding  gas  being  rendered  incandescent  by  the 
shock  of  the  explosion,  or  to  subsequent  inflaming  of  the  gases  of 
the  explosion. 

DETONATORS   AND  CAPS 

FULMINATE  OF  MERCURY,  (C*  N  •  O)2Hg,  the  composi- 
tion and  constitution  of  which  are  given  later  (see  Fulminic  Acid), 
FIG.  220.  wag  discovered  by  Howard  in  1799,  and  studied  as  regards  its 

100  grams  Gelatine  Dy-     constitution  by  Gay-Lussac,  Liebig,  Gerhardt,  Kekule,  etc.     The 
namite,  with  tamping      „.  •_  •    .  J    .     *«»«?  i_    -r\        -n 

of  wet  paper  rs^  mercurv  fulminate  cap  was  made  in  1815  by  Durs  Egg.     Its 

manufacture  requires  great  care  and  exact  proportions  of  the 

reagents.  So  long  as  fulminate  of  mercury  is  moist  it  presents  no  danger,  but  it  must  be 
handled  with  extreme  care  when  dry. 

It  is  best  prepared  by  Chandelon's  process  :  into  a  glass  vessel  of  about  4  litres  capacity 
is  placed  100  grams  of  mercury,  to  which  is  added  1000  grams  of  nitric  acid  of  40°  Be. 
(sp.  gr.  1-383),  the  liquid 'being  stirred  until  all  the  mercury  is  dissolved.  The  greenish 
liquid  is  allowed  to  cool  to  about  20°  and  is  then  poured  into  a  flask  of  at  least  5  litres 
capacity  containing  635  grams  of  90  per  cent,  alcohol ;  bumping  or  fuming  of  the  liquid 
is  of  no  consequence.  Very  soon  the  liquid  begins  to  boil  spontaneously,  to  become 
decolorised  and  to  evolve  gas  and  white  poisonous  vapours  (CO,  ethyl  nitrate  and  acetate), 
and  then  yellow  vapours  of  nitrogen  peroxide. 

The  mass  darkens  slightly,  and  when  the  maximum  fuming  occurs,  80  grams  of  90 
per  cent,  alcohol  are  added  a  little  at  a  time,  and  then  a  further  quantity  of  55  grams  of 
alcohol,  the  boiling  being  thus  somewhat  attenuated.  After  it  has  been  left  until  the 
white  vapours  have  disappeared,  there  appears  on  the  bottom  a  voluminous  whitish  powder, 
which  is  the  fulminate  of  mercury.  The  operation  lasts  altogether  fifteen  to  twenty  minutes, 
and  should  be  carried  out  under  a  hood  with  a  strong  draught,  or  else  the  flask  should  be 
fitted  with  a  stopper  and  wide  delivery  tube  to  carry  the  vapours  to  a  flue.  The  product 
is  poured  on  to  a  filter,  washed  ten  to  fifteen  times  with  water — until  the  wash- water  no 
longer  shows  an  acid  reaction  * — and  the  filter  with  the  fulminate  spread  out  on  other 
absorbent  paper  in  the  air  (not  in  the  sun)  until  it  is  almost  dry  (about  20  per  cent,  of 
moisture  being  left,  since  then  it  may  be  kept  safely  in  cardboard  boxes).  To  dry  it 
completely  and  safely,  vacuum  drying-ovens  at  a  temperature  below  40°  are  now  used. 

The  reaction  between  alcohol  and  mercuric  nitrate  begins  only  in  presence  (that  is, 
after  the  formation)  of  nitric  oxide,  the  alcohol  being  then  converted  into  aldehyde ;  indeed, 
if  the  alcohol  is  replaced  by  acetaldehyde  the  reaction  proceeds  better  and  more  completely 
(Munroe,  1912). 

Theoretically  100  grams  of  mercmy  should  yield  142  grams  of  the  fulminate,  but  practi- 
cally about  125  to  128  grams  are  obtained.  The  preparation  of  1  kilo  of  fulminate  requires 
8  kilos  of  alcohol,  which  is  only  partially  recovered  by  passing  all  the  vapour  emitted  during 
the  reaction  into  a  vessel  of  water.  In  the  dry  state,  it  is  sold  at  9s.  6d.  to  12s.  per  kilo ; 
when  not  used  at  once,  it  is  stored  under  water.  If  necessary,  it  may  be  purified  by  dis- 
solving in  hot  water  (solubility  1  :  130),  from  which  it  crystallises  on  cooling.  It  is  whitish 
or  sometimes  faintly  yellow  (if  a  small  quantity  of  HC1  or  NaCl  is  added  to  the  nitric  acid 
used  in  its  manufacture,  white  crystals  are  obtained),  poisonous  and  soluble  in  alcohol.2 

1  The  filtrate  and  the  wash-water  are  utilised  by  first  neutralising  with  milk  of  lime  or  calcium 
sulphide  (or  by  decomposing  with  hydrochloric  acid ) ;   from   the  precipitate  the  mercury  is 
recovered,  whilst  witheriteis  added  to  the  liquid  to  form  barium  nitrate ;  the  alcohol  is  recovered 
by  distillation. 

2  Analysis  of  Fulminate  of  Mercury  (Brownsdon's  method) :  the  fulminate  is  first  purified 
by  dissolving  it  in  potassium  cyanide  and  reprecipitating  it  with  dilute  nitric  acid ;  it  is  filtered, 
carefully  dried,  and  a  weighed  quantity  of  0-04  to  0-05  gram  dissolved  in  30  c.c.  of  water.     One 
gram  of  thiosulphate  is  then  added  and  the  liquid  shaken  and  made  up  to  100  c.c.  with  water. 
The  free  alkali  in  25  c.c.  of  this  solution  is  then  estimated  by  titration  with  N/10-sulphuric  acid 
in  presence  of  methyl  orange  as  indicator. 


DETONATORS 


309 


It  has  an  extraordinary  shattering  power  owing  to  its  very  great  rapidity  of  explosion. 
It  is  exploded  by  a  blow  or  by  brisk  rubbing,  and  gives  a  pressure  of  27,400  atmos.  When 
heated  slowly  it  explodes  at  152°.  All  objects  used  in  its  manipulation  must  be  of  wood, 
not  of  iron.  Since  it  is  scarcely  ever  used  alone  for  preparing  caps,  but  is  mixed  with  15  to 
20  per  cent,  of  potassium  chlorate  and  about  25  per  cent,  of  antimony  sulphide,  it  is  some- 
times, in  order  to  avoid  explosion,  made  into  a  paste  with  a  thick  solution  of  gum,  the 
required  quantity  being  poured  into  each  copper  cap  (which  contains  about  15  or  20  mgs. 
of  fulminate  for  sporting  caps,  or  1  to  1-5  grams  for  caps  to  be  used  with  dynamite  cartridges) , 
these  being  then  very  carefully  dried  in  vacuum  drying  ovens.  When,  however,  these 
mixtures  are  prepared  in  the  dry  state,  in  order  to  prevent  explosion  the  mixing  is  carried 
out  in  the  apparatus  shown  in  Figs.  221  and  222.  In  a  leather  box,  e,  a  leather  bag,/  (the 
so-called  "  jelly- bag  "),  is  suspended  by  the  loops,  h,  attached  to  the  gutta-percha  ring,  g. 
To  the  bottom  of  the  bag  and  to  the  ring,  g,  are  joined  several  cords  on  which  are 


FIG.  221. 


FIG.  222. 


threaded  rubber  rings,  alternately  large  and  small.  Another  cord,  n,  attached  to  the 
lever,  p  q  s,  admits  of  the  bottom  of  the  bag  being  raised  and  lowered  so  as  to  mix  the 
ingredients.  When  mixing  is  complete,  the  bottom  of  the  bag  is  drawn  completely  up,  so 
that  the  contents  fall  into  the  space  between  the  bag  and  the  box  and  thence  into  the 
collecting  vessel,  v. 

The  workman  is  protected  from  the  effects  of  a  possible  explosion  during  the  operation 
by  a  semi-cylindrical  wrought-iron  screen,  t.  The  caps  are  then  very  carefully  charged 
by  compressing  the  mixture  with  a  suitable  machine  or  press,  which  gives  a  pressure  rising 
gradually  to  260  atmos1.  (pure  fulminate  will  stand  7000  atmos.  without  exploding,  but  in 
presence  of  other  substances,  e.  g.,  sand  or  coke  powder,  or  other  hard  body,  it  will  explode 
with  a  very  small  pressure).  During  the  charging  the  operative  is  always  sheltered  by 
iron  screens. 

DETONATORS  (Caps,  Fuses).  Detonators  serve  to  produce  explosion  of  explosive 
substances.  For  black  powders  it  is  sufficient  to  produce  a  spark  in  the  mass  by  means 
of  a  heated  fuse,  but  with  nitroglycerine  or  guncotton  explosives,  neither  the  fuse  nor  the 
black  powder  causes  explosion,  ignition  being  the  most  they  produce.  In  these  cases 


310 


ORGANIC    CHEMISTRY 


use  is  made  of  fulminate  of  mercury  caps,  which  explode  by  simple  percussion  or  heat,  and 
produce  a  true  explosive  wave  capable  of  inducing  the  instantaneous  decomposition,  i.  e., 
the  explosion  even  of  large  masses  of  explosive,  provided  that  the  cap  is  of  suitable  size ; 
if,  however,  too  little  fulminate  is  used,  part  of  the  charge  does  not  explode.  Moist  or 
paraffined  compressed  guncotton  requires  more  powerful  caps  of  dry  guncotton,  these 
being  then  exploded  by  fulminate  of  mercury  detonators. 

Ignition  caps,  unlike  detonating  caps,  contain  also  a  little  potassium  chlorate. 

Smokeless  powders  require  ignition  caps  with  a  very  hot  flame,  which  is  obtained  by 
adding  to  the  fulminate  a  combustible  substance  or,  as  proposed  by  Brownsdon  and  the 
King's  Norton  Metal  Company,  a  little  powdered  aluminium. 

In  1900  Bielefeld  found  that  it  suffices  to  place  a  small  quantity  of  mercury  fulminate 
on  trinitrotoluene  or  other  aromatic  nitro-derivative  to  obtain  an  excellent  detonator, 
and  in  Germany  a  large  proportion  of  the  caps  have  a  basis  of  trinitrotoluene.  Tetranitro- 
methylaniline  (tetryl)  is  also  manufactured  as  a  detonator.  According  to  Wohler  and 
Matter  (1907),  the  fulminate  may  be  replaced  by  a  small  amount  of  silver  azide,  and  in 
1908  Hyronimus  suggested  lead  azide,  Pb(N3)2  (see  Vol.  L,  p.  376)  as  a  substitute,  but  thi? 
is  not  always  advantageous. 

Whereas  formerly,  for  kieselguhr  dynamite,  use  was  commonly  made  of  fulminate 
caps  No.  3,  and  only  in  exceptional  cases  of  No.  5  (double  strength),  nowadays,  especially 


FIG.  223. 


FIG.  224. 


FIG.  225. 


for  safety  explosives,  No.  6  caps  are  mostly  employed,  and  sometimes  No.  8  (2  grams  of 
mercury  fulminate)  to  obtain  complete  explosion. 

The  explosion  of  detonators  or  caps,  and  hence  of  the  cartridges  or  charges  of  explosive, 
both  in  blasting  and  military  operations,  is  effected  electrically  or  •with  fuses. 

Fuses  should  burn  with  a  definite  velocity,  so  as  to  allow  the  miners  to  reach  a  place  of 
safety  before  the  explosion.  This  requirement  is  satisfied  by  the  Bickford  fuses  (devised 
in  1831  by  the  Englishman,  Bickford).  These  consist  of  a  compact  cord  prepared  in  a 
special  manner  from  jute  or  cotton  threads,  which  are  spun  round  one  another  in  opposite 
directions  and  are  rendered  impermeable  by  tar  or  gutta-percha.  These  fuses  or  cords, 
5  mm.  thick,  have  an  empty  central  core,  which  is  then  filled  with  finely  granulated,  com- 
pressed powder.  They  then  burn  with  a  velocity  of  1  metre  in  ninety  seconds.  To  explode 
black  powder,  it  is  sufficient  to  fix  the  fuse  into  the  mass  of  the  charge,  which  explodes  as 
soon  as  the  flame  reaches  it. 

These  Bickford  fuses  became  of  practical  importance  only  in  1867,  when  the  use  of 
dynamite  in  mines  commenced. 

For  dynamite,  gelatine  dynamite,  and  explosive  gums  or  gelatines,  use  is  made  of  a 
fulminate  of  mercury  detonator  which  explodes  a  dynamite  cartridge,  this  then  causing 
explosion  of  all  the  other  cartridges  (without  caps)  surrounding  it.  The  fuse  is  cut  clean 
and  introduced  into  the  bottom  of  the  copper  cap  containing  the  fulminate,  and  is  fixed 
to  the  cap  by  squeezing  it  with  suitable  pincers  (Fig.  223).  The  parchment  paper  at  one 
extremity  of  the  cartridge  is  then  opened  and  the  cap  thrust  into  the  cavity  left  for  it 
(Fig.  224),  the  paper  being  then  tied  tightly  round  the  fuse  with  string  so  that  the  cap  and 
fuse  cannot  become  detached  from  the  cartridge  (Fig.  225). 


VARIOUS    POWDERS  311 

Ordinary  fuses,  which  are  very  irregular,  are  obtained  by  soaking  soft  cotton  cord  with 
lead  or  potassium  nitrate;  such  fuses  must  be  well  dried  before  use,  as  they  are  hygro- 
scopic. The  cord  may  also  be  impregnated  with  a  paste  of  gum  and  fine  black  powder  and 
then  dried.  Almost  instantaneous  fuses  may  be  made  from  guncotton. 

The  importance  of  tamping  after  the  introduction  of  the  cap  into  the  charge  has  already 
been  mentioned ;  if  the  explosion  is  carried  out  in  the  open,  the  charge  is  covered  with  earth 
or  stones. 

Electric  fuses  are  used,  especially  for  dynamite  and  fulminate  caps,  and  serve  well  for 
producing  the  simultaneous  explosion  of  several  charges,  this  giving  a  greater  effect  than 
separate  explosions ;  they  are  also  useful  in  galleries  which  contain  firedamp,  as  the  latter 
would  be  exploded  by  a  burning  fuse.  A  spiral  of  thin  platinum  wire  is  fixed  in  contact 
with  a  little  dry  guncotton  above  the  fulminate  of  the  cap.  The  two  ends  of  the  wire  are 
connected  separately  with  two  insulated  wires  joined  to  a  small  battery,  accumulator,  or 
hand  dynamo,  which  heats  the  wire  and  so  causes  explosion.  tJse  is  often  conveniently 
(since  the  fragile  platinum  spiral  is  eliminated)  made  of  an  electric  spark  formed  between 
two  platinum  points  very  near  to  one  another  in  a  mixture  of  potassium  chlorate  and 
antimony  sulphide  contained  in  the  cap ;  in  this  case  the  sparking  is  effected  by  a  device 
similar  to  a  Leyden  jar  (Bornliardt  exploder)  which  gives  a  high-tension  current,  or  by  one 
utilising  induced  currents  (Breguet  exploder) ;  these  may  be  placed  at  a  distance  from  the 
charge  by  lengthening  the  conducting  wires. 

At  one  time  ignition  was  effected  by  means  of  a  high  tension  current  from  a  frictional 
machine,  Breguet  alone  using  low  tension  current,  but  the  tendency  nowadays  is  to  employ 
the  latter,  together  with  magnetic  ignition,  the  danger  of  igniting  the  inflammable  gases 
of  mines  being  thus  diminished.  Formerly,  very  long  conducting  wires  could  not  be  used 
owing  to  the  weakening  of  the  current  at  the  igniting  extremities,  but  nowadays  relays  are 
inserted  at  various  points  and  maintain  the  current  constant. 

Lauer  and  Tirmann  make  friction  igniters,  which  are  operated  at  a  distance  by  means 
of  wires. 

Girard  obtains  detonating  fuses  by  filling  leaden  tubes  with  nitrohydrocellulose  and  then 
drawing  them  out  to  the  diameter  of  ordinary  safety  fuses.  Similar  fuses  were  made 
subsequently  to  1906  with  fillings  of  melinite  or,  better,  trinitrotoluene. 

The  best  of  these  fuses  are  those  with  instantaneous  ignition  proposed  by  General  Hess 
and  used  in  the  Austro-Hungarian  Army :  these  were  first  formed  of  four  threads  covered 
with  fulminate  of  mercury,  but  in  1903  Hess  rendered  their  action  slower  by  adding  20 
per  cent,  of  hard  paraffin  wax  to  the  fulminate. 

When  knotted,  these  instantaneous  fuses  behave  as  detonating  caps  and  electric  ignition 
may  be  dispensed  with ;  they  may  be  cut  and  beaten  without  danger. 

With  detonating  fuses  (1910)  containing  compressed  powdered  explosive  with  a  detona- 
ting velocity  of  5000  metres  per  second  (picric  acid  or  trinitrotoluene),  the  wick  is  bent 
and  the  bend  fixed  into  the  cap,  whilst  the  two  ends  are  brought  near  to  the  outside  and 
ignite  simultaneously.  Where  the  explosive  waves  meet  the  shock  is  such  that  the  waves 
reinforce  one  another,  producing  a  velocity  of  detonation  of  10,000  metres  per  second ;  in 
this  way  the  charge  is  more  completely  exploded. 

VARIOUS  POWDERS.  During  recent  years  there  has  been  very  keen  rivalry  between 
different  makers  to  prepare  new  powders  for  special  purposes  (even  for  shooting  pigeons  ! ), 
and  also  blasting  powders  more  economical  than  black  powder.  For  powders  to  be  used 
immediately  or  stored  in  very  dry  magazines,  the  potassium  nitrate  is  replaced  by  sodium 
nitrate  (although  this  is  more  hygroscopic),  which  is  cheaper  and  gives  a  larger  proportion 
of  oxygen;  the  charcoal  has  also  been  partially  replaced  by  other  organic  substances  (tar, 
sawdust,  flour,  and  even  horsedung).  These  powders,  often  short-lived,  are  given  most 
extravagant  names  (violette,  gunn,  fulopite,  pyrolite,  pudrolite,  etc.). 

Normanite  is  an  English  powder  for  use  in  mine  galleries,  and  is  composed  of  33  per  cent, 
nitroglycerine,  45  per  cent.  KNO3,  1-5  per  cent,  of  collodion- cotton,  8  per  cent,  of  wood- 
meal,  11  per  cent,  of  ammonium  oxalate,  and  1-5  per  cent,  of  wood  charcoal.  Faversham 
contains  80  to  90  per  cent,  of  ammonium  nitrate,  9  to  11  per  cent,  of  T.N.T.,  and  various 
other  products. 

Rexite  contains  7-5  per  cent,  of  nitroglycerine,  66  per  cent,  of  ammonium  nitrate,  14  per 
cent,  of  sodium  nitrate,  7-5  per  cent,  of  T.N.T.,  4  per  cent,  of  wood-meal,  and  .less  than  1 
per  cent,  of  moisture.  Ammonal,  which  was  used  as  a  shattering  explosive  during  the 


312  ORGANIC    CHEMISTRY 

European  War,  was  employed  first  in  mines,  and  contains  3  per  cent,  of  coarsely  powdered 
aluminium,  4  per  cent,  of  T.N.T.,  and  93  per  cent,  of  ammonium  nitrate.  It  was  proposed 
by  Escales  and  Dekmanin  1899-1900,  and  burns  slowly,  exploding  only  with  powerful  caps. 
Other  special  types  of  dynamite  are  mentioned  on  p.  284. 

DESTRUCTION  OF  EXPLOSIVES.  In  various  cases  it  is  necessary  to  destroy 
explosives,  when  these  have  altered  or  undergone  partial  decomposition,  or  when  residues 
are  left  from  samples  submitted  for  analysis.  With  black  powder  it  is  sufficient  to  im- 
merse it  in  water  and  so  dissolve  out  all  the  nitre,  and  then  to  burn  the  barely  dry  insoluble 
residue.  Water  does  not,  however,  destroy  nitroglycerine  or  the  various  dynamites ; 
with  these  the  caps  are  carefully  removed  and  also  the  wrapper  (including  the  parchment 
paper),  the  cartridges  being  placed  in  contact  one  with  the  other  on  a  long  strip  of  paper 
in  a  field  free  from  stones  and  away  from  any  building;  they  are  then  sprinkled  with 
petroleum,  and  a  long  fuse,  attached  to  the  first  cartridge,  lighted.  In  this  way  the  car- 
tridges burn  without  exploding.  With  frozen  dynamite  cartridges  which  have  undergone 
change,  it  is  dangerous  to  handle  them,  and  they  must  be  very  carefully  exploded  one  by 
one  in  the  open  with  a  fulminate  cap  and  fuse.  Nitroglycerine  may  be  made  into  a  paste 
with  sawdust  and  burnt  as  described  above.  Small  quantities  of  explosives  may  be 
burnt  in  pieces  the  size  of  a  pea,  and  small  dynamite  residues  may  be  decomposed  by 
heating  on  a  water-bath  and  frequently  stirring  with  concentrated  alcoholic  caustic  soda 
solution. 

STORAGE  AND  CARRIAGE  OF  EXPLOSIVES.  Explosives  factories  are  placed  at 
a  distance  of  about  1000  metres  from  any  dwelling-house  or  frequented  street.  The  ideas 
underlying  the  construction  of  magazines  are  very  varied.  In  some  countries  (Austria, 
Italy,  France,  and,  in  part,  Germany)  the  prepared  explosives  are  distributed  in  a  number 
of  small  magazines  far  from  the  factory,  and  constructed  of  wood  so  as  to  minimise  the 
danger  from  projection  in  case  of  explosion;  they  are  separated  by  large  mounds  of  earth 
as  high  as  the  magazine,  so  that  the  explosive  wave  or  projected  material  may  not  reach 
neighbouring  magazines.  Also  in  some  magazines  a  kind  of  wide  bridge  covered  with  earth 
is  constructed  over  the  magazine  to  annul  or  attenuate  the  effect  of  projectiles  falling  from 
above.  In  England,  however,  it  is  assumed  that,  owing  to  the  perfection  of  the  systems 
of  manufacture  and  of  chemical  and  physical  control  of  explosives,  explosion  is  not  to  be 
regarded  as  possible,  so  that  large,  very  solid  magazines  are  built,  either  wholly  of  cement 
or  partly  of  iron,  the  walls  being  half  a  metre  thick.  The  distance  between  the  separate 
magazines  varies  from  100  to  200  metres,-  according  as  the  amount  of  explosives  stored  is 
more  than  2000  or  10,000  kilos.  The  flooring  is  of  wood,  and  the  magazines  are  heated  in 
winter  by  means  of  steam-pipes  in  order  to  prevent  freezing  of  the  explosives.  In  general 
there  are  no  windows,  but  only  double  doors  and  small  apertures ;  artificial  illumination, 
which  is  rarely  used,  consists  of  lamps  placed  outside  the  apertures  or  electric  lamps  hermeti- 
cally sealed  with  gutta-perojaa  and  fitted  with  several  glass  coverings ;  in  some  cases  the 
electric  lamps  are  immersed  in  water. 

Any  person  entering  a  magazine  must  wear  felt  slippers  or  leather  boots  without  nails. 
The  most  serious  danger  is  not  that  of  accidental  explosion,  but  that  of  lightning.  When 
storms  threaten  all  work  is  suspended,  while  the  magazines  are  protected  from  lightning  by 
all  the  most  modern  appliances.1  Even  the  methods  of  packing  explosives  and  loading 

1  In  general  the  protection  afforded  by  lightning  conductors  is  due  to  the  fact  that  lightning 
is  rendered  harmless  if  it  meets  good  and  sufficiently  extensive  conductors  of  electricity.  There 
is,  however,  always  great  danger  if  inside  or  outside  the  buildings  protected  there  are  large  masses 
of  good  conducting  materials,  such  as  the  iron  and  lead  pipes  of  dynamite  factories,  as  these  may 
cause  deflection  of  the  lightning  even  from  its  path  in  the  lightning  conductors. 

At  the  Nobel  dynamite  factory  at  Krummel,  on  the  Elbe,  there  was  a  great  explosion  in  1900, 
lightning  striking  the  iron  compressed-air  pipe  and  being  thus  led  to  the  vessels  full  of  nitro- 
glycerine, which  consequently  exploded. 

Franklin's  principle,  according  to  which  a  metal  rod  furnished  with  points  should  serve  to 
discharge  to  earth  the  large  electric  charges  of  the  clouds,  is  not  applicable  to  the  protection  of 
explosive  factories,  since  such  rods  on  factories  do  not  discharge  the  clouds  to  a  sensible  extent, 
but  can  only  serve  to  conduct  the  lightning  to  earth  after  the  shock.  Much  more  rational  is 
Faraday's  method  of  attempting  to  discharge  the  electricity  of  the  clouds  or  to  conduct  the 
lightning  by  so  many  metallic  wires  as  to  prevent  it  from  subdividing,  no  secondary  circuits 
which  might  produce  sparks  being,  however,  formed.  According  to  Faraday,  the  most  certain 
protection  against  lightning  consists  of  a  metal  cage  surrounding  or  covering  the  building  to  be 
protected,  and  many  military  explosives  stores  are  effectually  protected  in  this  manner.  In 
1900,  Professor  Weber  proposed  the  protection  of  the  Krummel  explosives  factory  by  fixing  to 


ANALYSIS    OF    EXPLOSIVES  313 

them  on  wagons  for  transport  are  subject  to  detailed  regulations  :  by  legislation  dating 
from  1875  in  England  and  from  1905  and  1909  in  Germany,  and  in  Italy  by  a  series  of 
laws  and  regulations  of  various  dates.  In  every  case,  a  despatch  must  be  preceded  by  a 
permit  and  by  a  warning  to  all  the  stations  on  the  route.  Explosives  are  despatched  only 
on  certain  days  and  in  certain  trains.  In  Germany,  chlorate  and  perchlorate  travel  with- 
out restrictions.  Owing  to  the  great  stability  of  modern  explosives,  only  6  out  of  265 
accidents  due  to  explosives  occurred  during  transport. 

ANALYSIS  OF  EXPLOSIVES.  The  quantitative  determination  of  the  components  of 
black  powder  is  comparatively  simple  :  10  to  20  grams  of  the  sample  is  dried  in  an  oven 
until  constant  weight  (moisture)  and  is  then  extracted  with  hot  water,  which  dissolves 
the  nitre,  this  being  weighed  or  analysed  separately.  From  the  dried  residue  the  sulphur 
is  extracted  by  carbon  disulphide  in  a  Soxhlet  extraction  apparatus.  The  residue  then 
contains  the  charcoal,  graphite,  and  any  impurities  (sawdust,  mineral  carbon,  etc.)  which 
may  be  identified  under  the  microscope.  The  density  of  the  powder  is  determined  by 
means  of  a  densimeter,  and  the  size  of  the  grains  and  the  quantity  of  dust  by  suitable  sieves. 

The  analysis  of  dynamites  and  of  smokeless  powders  is  more  complicated  and  must  be 
carried  out  with  great  care.  In  dynamites  with  inert  bases  the  proportions  of  nitroglycerine, 
moisture,  and  inert  substance  are  determined  :  8  to  10  grams  of  the  dynamite,  cut  into  pieces 
the  size  of  peas,  with  a  wooden  or  bone  spatula,  are  weighed  on  a  clock-glass  and  left  in 
a  desiccator  over  calcium  chloride  (not  sulphuric  acid)  for  some  days  until  of  constant 
weight :  the  loss  in  weight  gives  the  moisture.  The  dried  mass  is  extracted  with  pure 
dry  ether  free  from  alcohol,  in  a  Soxhlet  apparatus  (as  in  the  extraction  of  fat,  which  see) , 
the  heating  being  effected  with  water  at  50°  to  60°  and  the  ether  subsequently  distilled  with 
water  at  40°  to  50°  away  from  the  neighbourhood  of  a  flame.  The  nitroglycerine  becomes 
turbid  when  almost  all  the  ether  is  evaporated,  but  clear  again  when  the  evaporation  is 
complete ;  the  nitroglycerine  is  dried  until  constant  in  weight  in  a  vacuum  desiccator  over 
calcium  chloride.  The  residue  left  in  the  extractor  (kieselguhr  or  other  inert  matter)  is 
dried  at  60°  to  70°  and  weighed.  It  is  spmetimes  sufficient  to  determine  the  nitroglycerine 
by  difference  from  the  weight  of  this  residue ;  the  result  is  exact  enough  and  the  operation 
more  rapid  and  less  dangerous. 

Dynamites  with  active  bases  sometimes  have  complex  compositions  and  the  analysis  is 
not  always  so  easy;  1  in  general,  the  nitroglycerine  and  collodion-cotton  are  separated 

iron  columns  galvanised  wire-netting  (88  meshes  per  sq.  metre)  furnished  with  metal  points  so 
as  to  form  a  kind  of  roof  a  metre  or  more  above  the  factory. 

The  columns  also  are  provided  at  the  top  with  metal  points  and  serve  to  conduct  the  electric 
discharge  to  the  earth.  In  the  wires  forming  the  network  sharp  curves  are  avoided  in  order  to 
facilitate  conduction  and  hinder  any  divergence  of  the  lightning.  Above  the  buildings  of  the 
Krummel  factory  there  are  24,000  metres  of  metal  wire  with  five  million  points,  which  may 
contribute  in  some  measure  to  discharge  the  clouds,  and  would  certainly  conduct  the  lightning 
to  earth  after  a  discharge.  The  ideal  method  would  consist  in  using  copper  wire  1  cm.  in  diameter, 
but  the  expense  of  this  would  be  enormous.  The  earth-contact  is  made  in  wet  places  with  iron 
plates  or  rails  one  or  two  metres  under  the  soil.  Also  the  metal  piping  (if  not  replaceable  by 
rubber  tubing)  and  apparatus  of  the  various  parts  of  the  factory  are  connected  with  the  earth- 
conductors  of  the  lightning  conductors,  so  as  to  avoid  the  formation  of  sparks  in  the  discharge 
of  the  lightning. 

It  has  also  been  suggested  that,  where  possible,  the  large  vessels  in  the  separate  buildings 
should  be  electrically  insulated,  both  from  the  lightning  conductors  and  from  the  earth. 

1  For  dynamites  with  active  bases  (containing  nitroglycerine,  collodion-cotton  or  guncotton, 
nitrates,  sawdust,  etc.),  Stillman  and  Austin  (1906)  propose  a  method  of  analysis  which  is  briefly 
as  follows  :  The  moisture  is  determined  on  10  grams  as  above ;  the  dry  mass  is  then  extracted 
several  times  in  the  cold  with  a  mixture  of  1  part  of  alcohol  and  2  parts  of  ether.  The  residue 
(.4)  is  dried  and  weighed  (for  its  analysis  see  later),  the  solution  being  left  to  evaporate  in  the 
cold  to  100  c.c.,  to  which  is  added  100  c.c.  of  chloroform  to  precipitate  the  collodion-cotton. 
The  liquid  is  decanted  on  to  a  tared,  dry,  cloth  filter  on  to  which  all  the  collodion-cotton  is  brought 
by  means  of  chloroform  ;  the  filter  is  dried  in  an  oven  at  40°  and  then  in  a  desiccator  and  weighed 
(as  a  check,  it  is  redissolved  in  alcohol  and  ether,  reprecipitated  with  chloipfonn,  collected  on  a 
filter  and  dried  at  40°,  the  collodion  being  then  detached  from  the  filter,  completely  dried  on  a 
watch-glass  in  a  desiccator  and  weighed).  After  the  collodion-cotton  is  separated,  the  decanted 
and  filtered  liquids  are  evaporated  in  a  tared  vessel,  dried  in  a  vacuum  and  the  remaining 
nitroglycerine  weighed. 

If  the  nitroglycerine  contains  traces  of  nitrates,  these  are  extracted  by  repeated  treatment 
with  small  quantities  of  water,  the  solution  being  then  evaporated  and  the  nitrates  weighed. 
If  along  with  the  nitroglycerine  there  are  also  resin,  paraffin  wax,  and  traces  of  sulphur,  it  is 
titrated  with  excess  of  normal  alcoholic  caustic  soda  in  the  hot,  the  excess  of  alkali  being  then 


314 


from  the  residue  by  alcohol  and  ether,  from  which  the  collodion-cotton  is  precipitated 
with  chloroform. 

The  resistance  to  heat  of  nitroglycerine  and  of  djTiamite  is  determined  as  with  nitro- 
cellulose (see  below),  the  nitroglycerine  being  extracted  from  dynamite  by  displacement 
with  water,  and  the  gelatine  explosives  being  mixed  with  double 
their  weight  of  chalk  prior  to  extraction  with  solvents;  it  should 
withstand  a  temperature  of  70°  for  at  least  fifteen  minutes  without 
colouring  starch  and  potassium  iodide  paper.  In  contact  with 
sensitive  blue  litmus  paper  it  should  not  give  the  slightest  reddening, 
as  this  would  indicate  incipient  decomposition. 

Exudation  of  nitroglycerine  from  dynamite,  in  either  the  cold  or 
the  hot,  shows  faulty  manufacture. 

With  nitrocellulose,  besides  testing  its  solubility  in  a  mixture  of 
1  part  of  alcohol  and  2  parts  of  ether  which  dissolves  collodion- 
cotton  but  not  guncotton,  the  nitrogen  is  often  estimated  in  the 
Lunge  nitrometer  (Vol.  I.,  p.  578)  by  shaking  with  concentrated 
sulphuric  acid;  or  Schlosing's  method,  as  used  in  France,  may  be 
employed  to  ascertain  the  type  of  the  nitrocellulose  :  in  a  150  c.c.  flask 
are  placed  25  grams  of  pure,  powdered,  ferrous  sulphate,  0-7  to  0-8 
gram  of  nitrocellulose,  and  70  to  80  c.c.  of  hydrochloric  acid;  the 
flask  is  shaken  and  then  fitted  with  a  stopper  through  which  pass  a 
delivery-tube  and  another  tube  conveying  a  current  of  carbon  dioxide ; 
when  all  the  air  is  expelled  the  delivery-tube,  dipping  into  a  vessel 
of  mercury,  is  covered  with  a  graduated  tube  filled  half  with  mercury 
and  half  with  caustic  soda  solution.  The  flask  is  then  heated  to 
boiling,  when  the  liquid  blackens  and  in  ten  minutes  all  the  nitric 

oxide  is  evolved,  the  last  traces  of  this  gas  being  driven  out  by  a  stream  of  carbon  dioxide. 
The  volume  of  gas  gives  the  amount  of  nitrogen. 

The  amount  of  non-nitrated  cotton  is  determined  by  boiling  5  grams  of  the  substance 
with  a  saturated  solution  of  sodium  sulphide,  the  liquid  being  decanted  after  a  stand  oi 
twenty-four  hours  and  the  treatment  with  sodium  sulphide  repeated ;  the  residue  is  finally 
collected  on  a  tared  cloth  filter,  washed  with  boiling  water,  then  with  dilute  hydrochloric 
acid,  and  lastly  with  boiling  water  again ;  it  is  then  dried  and  weighed. 

The  resistance  to  heat  (Abel's  heat  test)  of  nitrocellulose  is  of  importance,  as  it  serves  as 
a  control  during  manufacture  and  is  used  also  as  a  test  for  nitroglycerine  :  a  wide-mouthed 
glass  flask,  A  (Fig.  226),  20  cm.  in  diameter,  and  with  no  neck,  is  almost  filled  with  water 
and  is  covered  with  a  leather  disc  pierced  by  four  holes  provided  with  wire  clips  for  holding 
test-tubes ;  the  flask  is  heated  below  by  a  small  lamp,  F,  placed  under  a  metal  gauze  and 

determined  with  normal  acid  in  presence  of  phenolphthalein  :  1  c.c.  of  normal  alkali  used  in  the 
saponification  corresponds  with  0-0757  gram  of  nitroglycerine  (in  case  no  resin  is  present).  After 
the  titration,  the  liquid  is  evaporated  almost  to  dryness  to  eliminate  the  alcohol,  and  is  then 
diluted  with  water  and  shaken  with  ether  in  a  separating  funnel. 

The  ethereal  solution  is  separated  and  evaporated,  and  the  residual  paraffin  wax  weighed. 
The  aqueous  liquid  after  separation  of  the  ethereal  solution,  is  heated  with  a  little  bromine  to 
oxidise  the  sulphur;  it  is  then  acidified  with  HC1,  boiled,  and  the  resin  collected  on  a  tared  filter, 
whilst  in  the  filtrate  the  sulphuric  acid  formed  by  oxidation  of  the  sulphur  is  precipitated  with 
BaCU. 

The  nitroglycerine  may  be  estimated  by  difference,  by  subtracting  from  the  original  weight 
the  insoluble  residue,  A,  the  paraffin  wax,  the  resin,  the  small  amount  of  sulphur,  and  the  nitrates. 

The  residue,  A,  insoluble  in  alcohol  and  ether  (see  above),  is  extracted  with  hot  water;  the 
undissolved  part  is  dried  at  70°  and  weighed  (B  =  sawdust  +  sulphur  +  any  insoluble  mineral 
substances);  the  sulphur  is  extracted  with  carbon  disulphide,  and  weighed,  this  weight  sub- 
tracted from  B  giving  the  sawdnst,  from  which  also  the  weight  of  ash  left  after  calcining  is 
subtracted  if  inorganic  substances  are  present.  , 

The  aqueous  solution  obtained  from  A  is  evaporated,  dried  at  110°  and  weighed  (C  —  nitrates 
+  carbonates  +  any  woody  extract);  it  is  then  treated  with  a  little  nitric  acid,  evaporated, 
dried  and  weighed  (D) ;  from  the  difference  between  C  and  D  the  C02  evolved  and  hence  the 
carbonates  can  be  calculated. 

The  mass,  D,  is  melted,  heated  to  redness,  cooled,  treated  with  a  little  dilute  nitric  acid, 
evaporated,  dried  at  110°  and  weighed  (E);  this  weight  gives  the  sodium  and  potassium  nitrates. 
Subtraction  of  the  weights  of  nitrates  (E)  and  carbonates  from  C  gives  that  of  the  extractive 
matters  and  of  ammonium  nitrate,  if  this  is  present ;  the  latter  may  be  determined  in  the  aqueous 
liquid,  A,  by  estimating  the  ammonia  evolved  in  the  ordinary  way. 


PRESSURE    AND    HEAT    OF    EXPLOSION    3X5 

surrounded  by  a  screen,  D.  The  central  aperture  carries  a  thermometer,  and  one  of  the 
others  a  thermo-regulator  (if  necessary) ,  whilst  in  the  remaining  ones  are  placed  test-tubes 
which  contain  the  nitrocellulose  (1  to  3  grams)  or  nitroglycerine  (2  c.c.)  and  dip  into  the 
water.  Each  of  the  stoppers  of  the  test-tubes  is  fitted  with  a  hook  of  glass  tubing  on  which 
is  hung  a  piece  of  starch-potassium-iodide  paper  moistened  at  the  upper  part  with  a  drop 
of  dilute  glycerine. 

The  temperature  of  the  bath  is  maintained  at  82° ;  in  France  Powder  B  is  tested  at  110° 
and  in  other  countries  smokeless  powders  are  tested  up  to  130°,  a  current  of  air  being  passed 
over  the  heated  explosive.  The  test  is  finished  when  a  faint  brown  coloration  appears  at 
the  edge  of  the  glycerine.  A  good  guncotton  will  withstand  heating  at  82°  for  half  an  hour 
without  browning  the  paper. 

If  nitrocellulose  is  stabilised  by  the  incorporation  with  it  of  a  little  sodium  bicarbonate 
or  calcium  carbonate,  it  becomes  less  stable  to  the  Abel  test.1 

Measurement  of  the  Pressure  and  Heat  of  the  Gases  Developed  by  Explosives.  The 
power  of  an  explosive  is  deduced  principally  from  the  quantity  of  heat  produced  on  explosion 
(see  p.  259),  this  being  measured  in  the  Berthelot-Mahler  calorimetric  bomb  (see  Vol.  I., 
p.  461 ).  Deflagration  is  induced  by  means  of  an  electric  spark,  and  if  considerable  pressure 
is  maintained  in  the  bomb  by  means  of  air  (or  nitrogen  in  the  case  of  guncotton,  as  this  is 
deficient  in  oxygen,  which  should  not  be  supplied  if 
the  conditions  of  an  ordinary  explosion  are  to  be  repro- 
duced), the  products  of  deflagration  are  almost  identical 
with  those  of  explosion.  The  bomb  is  specially  con- 
structed with  various  accessories  to  allow  of  the  analysis 
and  measurement  of  the  gases  produced  in  the  decom- 
position, at  either  low  or  high  pressure,  of  the  explosive. 

The  pressure  of  the  gases  produced  by  the  explosion 
in  a  resistant  chamber,  C  (Fig.  227),  of  soft  sheet  steel 
wrapped  round  with  steel  wire,  is  measured  indirectly 
by  determining  the  crushing  of  a  small  copper  cylinder, 
Z  (crusher),  13  mm.  high  and  8  mm.  in  diameter,  placed 
between  a  fixed  base,  d,  and  a  hardened  steel  piston,  a, 
of  known  surface  which  transmits  the  pressure  of  the 
gases.  The  chamber,  C,  is  fixed  by  two  massive  wrought- 
iron  plates,  D  and  D',  held  together  by  six  thick 
rods,  B. 

Deflagration  is  caused  by  rendering  incandescent  a 
platinum  wire  between  the  two  terminals,  b.     In  order 
to   obtain  exact  results  it  is  indispensable  that  there 
be    no    escape    of    the    gas,   which    would    also    cause 
gas  being  at  a  temperature   of  2000°  to   3000°  and 
atmospheres. 

The  deformation  of  the  crushers  is  shown  in  almost  the  natural  dimensions  in  Fig.  182 
on  p.  262. 

The  sensitiveness  of  explosives  to  a  blow  is  determined  empirically  by  allowing  a  given 

1  According  to  Will  (1902)  and  Egerton  (1913),  this  test  is  very  sensitive,  being  able  to  detect 
0-0000016  gram  of  nitrous  acid  in  100  grams  of  explosive.  However,  some  years  ago  certain 
English  manufacturers  added  various  substances  (e.g.,  mercuric  chloride,  formaldehyde,  etc.) 
to  mask  the  instability  of  their  powders.  It  must  also  be  borne  in  mind  that  the  sensitiveness 
of  the  reaction  may  be  influenced  by  the  method  of  preparation  of  the  starch-iodide  powder. 
The  test  is  carried  out  in  a  pure  atmosphere  removed  from  the  smallest  traces  of  nitrous  acid 
vapour.  Since  decomposition  in  powders  is  gradual,  the  duration  of  the  test  (e.  g.,  thirty  minutes ) 
should  be  noted. 

Angeli  test  :  When  explosives  with  a  basis  of  nitric  esters  contain  solvent  (ether,  alcohol, 
acetone,  etc. )  or  stabilising  substance,  the  Abel  test  is  insufficient,  since  the  reaction  of  the  nitrous 
vapours  is  prevented  or  retarded.  In  1917  Angeli  proposed  to  replace  the  Abel  test  by  a  qualita- 
tive test  of  the  acidity  carried  out  as  follows  :  A  portion  of  the  powder  cut  into  thin  flakes  is  shaken 
in  a  test-tube  with  water  containing  a  few  drops  of  a  0-2  per  cent,  alcoholic  solution  of  dimetliyla- 
mincazobenzene,  q.v>,  Part  III);  if  the>  flakes  remain  yellowish,  they  are  not  acid  and  have  kept 
well,  but  if  they  turn  red,  they  are  acid  and  have  undergone  alteration. 

Silvered  vessel  test:  This  is  used  in  England  and  Italy,  and  consists  in  determining  the  number 
of  hours  required  for  the  temperature  of  the  explosive  kept  in  a  silvered  flask  (100  c.c.  or  up  to 
3000  c.c.)  in  a  thermostat  at  80°  to  rise  by  2°. 


FIG.  227. 

danger    from    projection,    the 
a  pressure  of  several  thousand 


316 


weight  of  iron  (ram,  see  Fig.  228)  to  fall  from  various  heights  on  to  a  certain  amount  of 
explosive  placed  on  an  iron  block,  the  height  of  the  fall  being  increased  until  explosion  occurs. 
The  sensitiveness  to  heat  is  measured  roughly  by  throwing  small  pieces  of  the  explosive  on 
to  mercury  heated  to  successively  increasing  temperatures  until  deflagration  takes  place. 
When  the  power  of  an  explosive  cannot  be  determined  directly  or  by  comparison  of  the 
practical  effects,  indirect  tests  must  be  employed,  although  these  do  not  always  correspond 

with  the  actual  effects.     To  avoid  uncertainty,  the  expression 

power  of  an  explosive,  f,  is  applied  to  the  product  of  the  volume, 
v0,  of  gas  (reduced  to  0°  and  formed  from  unit  weight  of  the 
explosive),  the  pressure,  p0,  in  mm.,  and  the  absolute 
temperature,  T  (calculated  from  the  products  of  the  reaction), 
this  product  being  divided  by  273,  so  that : 


FIG.  228. 


.     273  ' 

The  power  of  progressive  explosives  may  be  determined 
indirectly  by  Guttmann's  power  gauge  (Fig.  229) :  on  a  hollow 
block  of  steel,  a,  (diameter  of  cavity  35  mm.),  are  screwed  two 
steel  blocks,  b,  and  a  small  firing-plug,  g.  A  trigger,  m,  which 
can  be  released  from  a  distance  by  means  of  a  cord,  serves  to 
explode  the  plug.  The  apparatus  is  charged  by  unscrewing  one 
of  the  blocks,  b,  and  introducing  first  a  cylinder  of  drawn  lead, 
40  mm.  long  and  35  mm.  in  diameter,  which  closes  hermetically 
the  wide  mouth  of  the  right-hand  cone :  then  a  steel  disc  and 
one  of  cardboard  of  such  thickness  that  it  makes  20  grams  of 
powder  rest  just  in  the  middle.  This  powder,  which  is  intro- 
duced next,  is  situate  just  under  the  cap,  n.  Then  follow  a  disc 
of  cardboard,  one  of  steel,  and  a  block  of  lead  similar  to  the  first, 
this  closing  the  cavity  to  the  left,  when  the  block,  6,  is  again 
screwed  on.  The  gases  produced  by  the  explosion  have  no 
outlet,  and  so  force  the  leaden  blocks  into  the  conical  holes  to 
the  right  and  left.  The  height  of  the  leaden  cones  projecting  is 
compared  with  that  obtained  with  a  standard  explosive  and  thus 
gives  the  power  of  the  explosive. 

For  shattering  explosives,  on  the  other  hand,  good  results 
are  obtained  with  Trauzl's  lead  block,  which  is  in  the  form  of 
a  cylinder  200  mm.  in  height  and  diameter.  In  the  middle 


FIG.  229. 


is  a  cavity,  110  mm.  deep  and  20  mm.  wide,  into  which  15  to  20  grams  of  the  explosive 
is  placed.  A  fulminate  cap,  connected  with  wires  for  firing,  is  inserted  and  the  bore 
tamped  with  well-compressed  sand  and  chalk.  After  the  explosion,  the  capacity  of  the 
cavity  is  measured  with  water.  Fig.  230  shows  several  of  these  blocks  after  testing  with 
various  explosives.  A  charge  of  15  grams  of  No.  1  dynamite  gives  a  volume  of  705  c.c.,  and 
deducting  from  this  30  c.c.  for  the  original  volume,  and  30  c.c.  produced  by  the  1-5  grams 


VELOCITYOF    PROJECTILES  317 

of  fulminate  in  the  cap,  there  remains  645  c.c.  due  to  the  explosive,  i.  e.,  43  c.c.  per  gram. 
To  obtain  comparable  results  with  explosives  of  the  same  class,  charges  of  equal  weights 
must  be  taken,  otherwise  different  values  are  obtained  for  the  same  explosive;  there  are, 
besides,  other  causes  of  error,  which  give  only  a  relative  value  to  this  method  of  determining 
the  power. 


I  •  \ 


FIG.  230. 

Measurement  of  the  Initial  Velocity  of  Projectiles.  For  this  purpose  use  is  made  of 
Le  Boulenge's  chronograph  (Figs.  231  and  232),  which  gives  the  velocity,  V,  by  measuring 
the  time,  T,  taken  by  the  projectile  to  traverse  the  known  distance,  D  (20  to  50  metres), 
between  two  wire  frames,  G,  G'  (Fig.  231),  which  are  cut  through  by  the  projectile  im- 
mediately after  it  leaves  the  gun  and  are  connected  electrically  with  two  quite  distinct  points 
of  the  chronograph,  the  apparatus  being  so  arranged 

that  T  lies  between  0-05  and  0-15  second;   V  =  w. 

The  chronograph  is  formed  of  two  electro-magnets, 
a  and  e  (Fig.  232,  or  C  and  C',  Fig.  231),  joined  to 
the  batteries  B  and  B',  and  to  the  corresponding 


FIG.  231. 


FIG.  232. 


wire  frames,  G  and  G'.  The  magnet,  a,  attracts  a  tubular  bar  (c,  d,  Fig.  232,  or  C,  Fig.  231 ) 
of  the  chronometer,  which  terminates  at  the  top  in  a  soft  iron  point  and  is  enlarged  at  the 
bottom ;  the  magnet,  e  (or  A'  in  Fig.  231 ),  attracts  a  rod,/  (or  C",  Fig.  231 ),  of  the  registrar. 
The  chronometer  bar  is  surrounded  by  a  thin  zinc  or  copper  tube.  The  registrar  is  of  soft 
iron,  has  the  same  weight  as  the  chronometer,  and  is  pointed  at  the  top  and  enlarged  at 
the  bottom.  When  the  projectile  traverses  the  first  frame,  G,  it  interrupts  the  current 
of  the  electro -magnet,  A,  and  the  chronometer  bar,  C,  becomes  detached  from  A  (Fig.  231) 
and  begins  to  fall  freely.  When  it  traverses  the  second  frame,  G',  it  interrupts  the  current 


318  ORGAN  1C    CHEMISTRY 

of  the  electro-magnet,  A',  and  the  registrar,  C',  falls  and  releases  a  hook  which  liberates  a 
horizontal  spring  pointer,  this  immediately  striking  the  falling  chronometer  bar.  The 
mark  on  this  bar  will  be  the  higher  the  lower  the  initial  velocity  of  the  projectile.  Suitable 
tables  deduced  from  simple  formulae  1  give  the  required  velocity. 

The  velocity  of  detonation  is  difficult  to  determine,  since  it  depends  largely  on  the  resist- 
ance of  the  enclosure  containing  the  explosive  and  on  other  circumstances.  It  is  determined 
roughly  but  with  sufficient  exactitude,  under  similar  conditions,  by  placing  a  number  of 
cartridges  in  a  continuous  row  and  joining  the  two  wires  of  the  Le  Boulenge  chronograph 
to  points  in  the  row  at  a  certain  distance  apart. 

USES  OF  EXPLOSIVES.  The  largest  consumption  of  explosives  is  that 
of  armies  and  navies,  whilst  in  various  civil  operations  these  substances  are 
also  employed  :  in  the  tunnelling  of  mountain  ranges ;  in  lessening  manual 
labour  in  the  ploughing  -of  the  soil ;  for  disintegrating  rocks  to  provide  material 
for  the  construction  of  houses  to  displace  the  all  too  numerous  deserts;  and 
further,  for  preparing  blocks  of  material  to  be  wrought  by  the  genius  of  man  into 
monuments  attesting  to  posterity  the  varied  and  incessant  progress  of  human 
thought  and  labour. 

In  practice  a  sharp  distinction  is  made  between  progressive  explosives,  used 
more  especially  in  mines  for  detaching  large  masses  of  rock  and  for  excavating 
(for  coal,  minerals,  gold,  and  diamonds),  and  shattering  explosives  (dynamite, 
etc.),  employed  for  such  purposes  as  demolishing  walls,  bridges,  and  large  trees, 
or  breaking  the  ice  at  the  surface  of  rivers  and  lakes  when  navigation  is  pre- 
vented. To  demolish  a  large  tree  it  is  sufficient  to  surround  it  with  a  string 
of  dynamite  cartridges,  explosion  of  one  of  which  will  cause  explosion  of  the 
others ;  to  break  iron,  e.  g.,  a  railway  rail,  or  cut  a  bridge,  one  or  more  cartridges 
are  placed  on  it,  covered  with  a  light  tamping  of  earth  and  exploded.  In  sub- 
aqueous works  modern  smokeless  explosives  are  of  great  service,  since  to  their 
great  power  is  added  their  stability  towards  water,  which  acts  as  an  excellent 
tamping. 2 

The  use  of  explosives  in  agriculture,  particularly  with  the  view  of  utilising  the  enormous 
stocks  remaining  in  all  countries  after  the  European  War,  has  become  an  accomplished 
fact.  As  early  as  1870  De  Hamm  of  Vienna  anticipated  the  employment  of  dynamite 
in  agriculture,  and  in  1878,  Sobrero,  in  a  communication  to  the  Turin  Academy  of  Sciences, 

1  A  test  is  first  made  in  which  the  chronometer  bar  and  the  registrar  fall  simultaneously. 
The  height,  h,  at  which  the  former  is  struck  corresponds  with  a  time,  t,  which  must  always  be 
allowed  for  in  the  subsequent  measurements,  as  it  represents  the  time  required  by  the  registrar 

to  release  the  spring.     According  to  the  law  of  bodies  falling  freely,  h  =  lgtz,  so  that  t  —  \J  ~_ ; 

in  practice,  when  a  time,  T,  elapses  during  the  passage  of  the  projectile  from  G  to  G',  the  mark 

/2// 
on  the  chronometer  bar  at  the  height,  H,  corresponds  with  a  time,  T  +  t  =  \J  —  .    The  difference 

v     ff 

between  these  two  measurements  gives  the  time  required,  the  velocity  being  then  deduced  from 

D 
the  formula  :    V  = 

2  The  Mont  Cenis  tunnel,  which  connects  Italy  and  France,  and  is  12,233  metres  in  length,  was 
commenced  in  August  1857  and,  as  it  was  assumed  that  the  blasting  would  be  carried  out  with 
black  powder,  it  was  calculated  that  twenty-four  years  would  be  required  to  complete  the  work. 
After  1865,  however,  dynamite  became  available,  and  the  work  was  finished  eleven  years  earlier 
than  was  anticipated,  1000  tons  of  explosive  being  used  and  £2,800,00'0  expended.     The  St. 
Gothard  tunnel  (14,920  metres),  joining  Italy  and  Switzerland,  was  completed  in  six  years  and 
a  half  (1873-1880),  and  cost  £10,400,000. 

During  the  piercing  of  the  Simplon,  1640  tons  of  gelatine  explosives  were  used,  mostly  with 
a  content  of  about  92  per  cent,  of  nitroglycerine.  In  constructing  the  harbour  of  Genoa,  the 
Nobel  Company  exploded  simultaneously  a  number  of  mines  with  a  total  charge  of  6000  kilos 
of  dynamite.  For  the  removal  in  1905  of  a  rock  that  partially  obstructed  the  Danube  at  Greisen- 
stein,  a  mine  was  laid  with  11,700  kilos  of  dynamite;  280,000  cu.  metres  of  rock  were  detached 
at  a  cost  of  about  three-halfpence  per  cubic  metre.  In  the  American  Independence  Day  fetes, 
a  million  pounds  worth  of  fireworks  are  consumed  every  year. 


FATTY    ACIDS  319 

made  definite  proposals  in  this  direction.  Various  practical  applications  were  afterwards 
made  in  America,  Germany  and  elsewhere,  and  in  1918-1919  rigorous  and  systematic  tests, 
carried  out  by  specialists  in  America,  France  and  Italy  (with  trinitrotoluene  and  picric 
acid)  showed  that  highly  compact  and  semi-rocky  soils  may  be  broken  down  satisfactorily 
in  this  way ;  cartridges  of  100  or  200  grams  were  placed  less  than  1£  metres  apart  at  a  depth 
of  about  60  cm.,  good  tamping  being  provided.  Explosives  are  used  economically  only 
when  the  usual  means  present  great  difficulties. 

In  the  United  States  a  single  factory  produced  in  1911  explosives  to  the  value  of  £120,000 
for  agricultural  purposes. 

STATISTICS  OF  EXPLOSIVES.  The  consumption  of  explosives  in  time  of  war  is 
enormous.  Every  shot  of  a  large  gun,  which  does  not  always  hit  the  mark,  costs  hundreds 
of  pounds. 

The  world' 's  production  of  explosives  prior  to  the  European  War  reached  a  total  of  350,000 
to  400,000  tons,  almost  the  half  of  this  amount  being  made  in  the  United  States.  According 
to  O.  Guttmann,  the  production  of  explosives  with  nitroglycerine  as  base  amounted  in 
1909  to  more  than  62,000  tons,  distributed  as  follows  :  United  States,  20,000  tons  (in  1912, 
over  22,000  tons);  Ger man y,  10,300;  England,  8100;  the  Transvaal,  8000 ;  Canada,  5000; 
Spain  and  Portugal,  3500 ;  Austria-Hungary,  2300;  France,  1500;  Switzerland,  Australia, 
and  Norway  and  Sweden,  600  each;  Russia,  Italy,  and  Holland  and  Belgium,  about  500 
each;  and  Greece,  175  tons.1 

EE.   ACIDS 

I.  SATURATED   MONOBASIC   FATTY   ACIDS,   CnH2n02 

These  are  termed  fatty  acids  because  some  of  them  are  contained  in  fats,  from 
which  they  are  prepared.  All  contain  the  characteristic  group,  — C02H,  the 

1  The  output  of  military  explosives  in  different  countries  in  1913  and  during  the  first  two  years 
of  the  European  War  is  shown  approximately  by  the  following  figures  (tons) : 

Great  United  Whole 

Britain  Germany  France  Italy  States  Eussia  Japan  Austria  world 

1913       .      18,000  60,000  15,000  3,500  8,000  6,000  4,000  5,000  150,000 

1915  .     120,000  360,000  160,000  15,000  130,000  60,000  50,000  90,000  1,065,000 

1916  .    200,000  540,000  300,000  45,000  190,000  100,000  90,000  150,000  1,805,000 

In  addition  to  its  enormous  home  consumption,  Germany  exported,  in  1906,  2136  tons  of 
black  powder,  of  the  value  £320,000 ;  4791  tons  of  other  explosives,  worth  £372,000 ;  and  7300 
tons  of  cartridge  charges  for  guns  and  artillery,  of  the  value  £1,000,000.  In  1913  the  total 
German  exports  of  explosives  were  valued  at  £4,000,000  and  the  imports  at  £72,000.  The  out- 
put of  dynamite  in  Germany  was  2000  tons  in  1880,  4000  in  1890,  8000  in  1909,  and  11,000,  besides 
15,000  of  safety  explosives  with  a  basis  of  ammonium  nitrate,  in  1912.  Before  the  war,  some  of 
the  German  explosives  factories  paid  dividends  of  25  per  cent,  or  more. 

In  the  United  States  the  industry  is  a  rapidly  growing  one.  While  the  total  production  was 
£3,400,000  (including  40,000  tons  of  dynamite)  in  1900,  it  rose  in  1905  to  £5,920,000,  of  which 
£1,760,000  represented  black  powder;  £320,000  nitroglycerine ;  £2,600,000  dynamite ;  £800,000 
smokeless  powder;  and  £35,200  guncotton. 

In  1909  the  capital  invested  in  explosives  works  in  the  United  States  amounted  to  £10,000,000, 
the  output  comprising  85,000  tons  of  dynamite,  4500  tons  of  safety  mine  explosives,  14,000  tons 
of  nitroglycerine,  6000  tons  of  black  powder,  45,000  tons  of  shattering  explosives,  etc.,  the  total 
value  being  £8,000,000  (in  1904,  £6,000,000),  and  the  power  used  28,600  horse-power. 

During  the  period  of  their  neutrality,  the  United  States  manufactured  enormous  quantities 
of  explosives  for  home  consumption  and  for  the  Allies,  especially  France,  Great  Britain,  and  Russia. 
About  205,000  tons  were  made  for  home  consumption  in  1915,  and  more  than  225,000  tons  in 
1916;  the  value  of  the  exports  was  £2,000,000  in  1914  and  £153,400,000  in  1916.  When  the 
European  Allies  became  able  to  supply  their  own  needs,  the  American  factories  continued  to 
produce  on  an  even  vaster  scale  for  the  needs  of  their  own  country  in  the  war. 

In  1910  Great  Britain  exported  630  tons  (£172,000)  of  smokeless  powders  and  7200  tons 
(£720,000)  of  dynamite,  450  tons  (£37,600)  of  the  latter  being  imported.  In  1907,  Great  Britain 
consumed  7000  tons  of  black  powder  and  exported  3597  tons  (3500  in  1910 ).  Before  the  European 
War  single  factories  in  England  made  as  much  as  10,000  tons  of  dynamite  per  annum. 

Japan,  which  before  the  war  possessed  two  Government  factories  for  military  explosives,  im- 
ported from  Great  Britain  and  Germany  various  explosives,  to  the  value  of  £100,000,  in  1910. 

In  Belgium  the  consumption  of  mining  explosives  in  1910  was  about  1473  tons,  229  tons  being 
black  powder. 

In  the  same  year  Austrian  mines  used  about  2395  tons  of  different  explosives,  1600  tons  being 
dynamites  of  various  types,  while  in  the  Transvaal  mines  explosives  to  the  value  of  £1,440,000 
were  consumed. 


320 


ORGANIC    CHEMISTRY 


hydrogen  of  which  is  replaceable  by  metals.  With  every  hydrocarbon  or  every 
primary  alcohol  of  the  methane  series  corresponds  a  monobasic  fatty  acid. 
The  first  members  are  liquids  having  a  pungent  odour,  and  are  soluble  in  water, 
alcohol,  or  ether,  and  boil  without  decomposing ;  then'  follow  members  of  an 
oily  consistency,  less  soluble  in  water,  and  with  unpleasant  smells  like  that  of 
rancid  butter  or  perspiration ;  beyond  C10  they  are  solid,  insoluble  in  water, 
and  soluble  in  alcohol  or  ether,  and  distil  unchanged  only  in  a  vacuum.  The 
first  members  (up  to  C9  or  C10)  are  volatile  in  steam. 

It  will  be  seen  from  the  Table  that  the  boiling-points  of  these  acids  rise 
regularly  with  increase  in  the  number  of  carbon  atoms,  but  the  melting- 
points  are  higher  in  an  acid  with  an  even  number  of  carbon  atoms  than  in  those 
immediately  below  and  above  with  uneven  numbers. 

TABLE  OF  THE  SATUKATED  MONOBASIC  FATTY  ACIDS 


Formula 

Name 

Melting-point 

Boiling-point 

Specific  gravity 

CH202 

Formic 

+    8-3° 

101° 

1-2187  (20°) 

C2H402 

Acetic 

+  16-5° 

118° 

1-0502  (20°) 

C3H6O2 

Propionic 

-  22° 

141° 

1-013  (0° 

CTT   (~\ 

(Normal  butyric 

-    7-9° 

162° 

0-978  (0° 

4n8U2 

\Isobutyric 

-  79° 

154° 

0-965  (0° 

Normal  valeric 

-  58-5° 

185° 

0-956  (0° 

C  H     O 

Iso  valeric 

-51° 

„  174° 

0-947  (0° 

Trimethylacetic 

+  34°-35° 

163° 

0-905  (50°) 

* 

Methylethylacetic 

— 

173°-174° 

0-938  (20°) 

C6H12°2 

Normal  caproic  (hexoic) 

1-5° 

205° 

0-945  (0° 

1 

C7H1402 

Normal  heptoic 

-  10° 

223° 

0-921  (15°) 

C8H16°2 

Caprylic  (octoic) 

+  16-5° 

237-5° 

0-910  (20°) 

C9H18°2 

Pelargonic  (nonoic) 

+  12-5° 

186°  \          0-911  (12°) 

C10H20°2 

Capric  (decoic) 

+  31-4° 

200° 

aj     0-930  (37°) 

C11H22°2 

Undecoic 

28° 

212° 

H 

p 

— 

C12H24°2 

Laurie 

44° 

225° 

1     0-875      \ 

"s 

C13H26O2 

Tridecoic 

40-5° 

236° 

O<                     

'3 

C14H28°2 

Myristic 

54° 

248° 

0 

0-862 

tUD 

C15H30°2 

Pentadecoic 

51° 

257° 

a 

— 

•S 

Palmitic 

62-6° 

268° 

8 

0-853 

"5 

C17H34°2 

Margaric 

60° 

277° 

49 

— 

S 

C18H36O2 

Stearic 

69-3° 

287° 

0-845       J 

<! 

C19H38°2 

Nonadecoic 

66-5° 

298°  J 

— 

C20H40°2 

Arachidic     , 

77° 

— 

— 

C22H44°2 

Behenic 

84° 

360°/60  mm. 

— 

C24H48O2 

Lignoceric 

80°-81° 

— 

— 

^26^52^2 

Cerotic 

78-5° 

— 

— 

C30H60°2 

Melissic 

91° 

— 

GENERAL  METHODS  OF  PREPARATION,  (a)  In  dealing  with  primary 
alcohols  and  aldehydes,  it  was  shown  how  simple  oxidation  of  these  compounds 
yields  the  corresponding  acids  containing  the  same  number  of  carbon  atoms, 
whilst  when  secondary  and  tertiary  alcohols  or  ketones  are  oxidised,  the  chain 
is  broken  and  acids  with  a  less  number  of  carbon  atoms  are  obtained. 

(b)  Hydrolysis  of  the  nitriles  (see  these)  in  the  hot  with  potassium  hydroxide 
or  with  mineral  acids  yields  the  amides  (see  these)  as  intermediate  compounds, 
and  then  the  acids  with  one  carbon  atom  more  than  the  alcohols  from  which 
the  nitriles  originate  : 


CH3  •  CN  -f  2H20  =  NH3  +  CH3 


C02H. 


PROPERTIES    OF    FATTY    ACIDS  321 

(c)  The  interaction  of  a  zinc-alkyl  with  phosgene  gives  : 

Zn(CH3)2  +  2COC12  =  ZnCl2  +  2CH3  •  COC1  (Acetyl  chloride), 
which  on  decomposition  with  water  gives  : 

CH3  •  COC1  4-  H2O  =  HC1  +  CH3  •  C02H. 

(d)  When  a  hydroxy-acid  is  heated  with  hydrogen  iodide,  separation   of 
water  and  iodine  occurs  and  a  fatty  acid  is  formed. 

(e)  Other  general  reactions  are  those  of  Grignard  (see  pp.  33,  243),  those 
of  ethyl  acetoacetate  and  ethyl  malonate  (see  these),  and  those  of  elimination 
of  C02  from  dibasic  acids  (containing  two  carboxyls,  CO'OH)  and  of  addition 
of  hydrogen  to  unsaturated  acids,  etc. 

PROPERTIES.  In  aqueous  solution  the  acids  are  electrolytically  dis- 
sociated into  the  cations  H  and  the  anions  R'C02  (see  Vol.  I.,  p.  94). 

Substitution  of  this  ionic  hydrogen  by  a  metal  yields  salts,  which  in  aqueous 
solution  (when  they  are  soluble)  are  almost  completely  dissociated,  whilst  the 
hydrogen  of  the  hydroxyl  group  of  the  alcohols  is  also  replaceable  by  a  metal 
(alkoxide),  but  the  resulting  alkoxide  is  decomposed  by  water  (hydrolysed). 

The  strength  of  an  acid  (or  its  power)  may  always  be  determined  from  the 
degree  of  dissociation  (Vol.  L,  pp.  95,  102),  this  decreasing  in  the  following 
order  :  formic,  acetic,  propionic,  normal  butyric,  valeric,  etc. ;  thus,  with  rise 
of  the  molecular  weight  the  dissociation  diminishes. 

The  hydroxyl  group  of  the  carboxyl  group,  — CO  •  OH,  may  sometimes  be 
substituted  by  halogens  (especially  by  chlorine,  by  the  action  of  PC15,  which 
forms  acid  chlorides  or  chloroanhydrides,  e.g.,  acetyl  chloride,  CH3'COC1). 

Substitution  of  the  hydroxyl,  (1)  by  SH,  gives  thio-acids,  and  (2)  by  NH2 
yields  the  amides,  e.  g.,  acetamide,  CH3  •  CO  •  NH2  (by  heating  ammonium 
acetate) ;  under  certain  conditions  these  compounds  all  give  the  acids  from 
which  they  originate. 

It  has  already  been  mentioned  that  the  saturated  hydrocarbons  are  formed 
by  the  electrolysis  of  the  alkali  salts  of  the  corresponding  acids,  with  elimination 
of  CO2,  H,  and  0  (the  last  two  from  the  water  present  as  solvent)  and  also  of 
secondary  products  (unsaturated  ethers  and  hydrocarbons ) ;  if  the  electrolysis 
is  effected  without  a  diaphragm,  alkali  carbonate  and  bicarbonate  are  formed, 
and  hence  also  a  loAver  alcohol.  Carbon  dioxide  may  also  be  eliminated,  and 
hydrocarbons  thus  formed,  from  the  alkali  salts  of  the  acids  by  heating  in 
presence  of  soda-lime  or  baryta,  or  by  reducing  the  acids  with  hydriodic  acid 
and  phosphorus. 

If,  however,  the  calcium  salts  of  the  acids  are  distilled,  with  or  without 
P205,  the  principal  product  is  a  ketone  formed  from  two  molecules  of  the  acid  : 

(CH3  •  COO)2Ca  =  CaCO3  +  CH3  •  CO  •  CH3 ; 

if  the  calcium  salt  is  heated  in  presence  of  calcium  formate,  the  aldehyde 
corresponding  with  the  higher  acid  is  formed. 

The  halogens  also  replace  the  hydrogen  of  the  alkyl  residues  of  the  acids, 
giving  products  which  surpass  in  acid  properties  the  acids  from  which  they  are 
formed.1  By  heating  the  acids  homologous  to  acetic  acid  (which  are  very, 

1  Besides  referring  to  what  has  been  stated  in  Vol.  I.,  pp.  98  et  seq.,  we  may  here  quote  the  very 
clear  consideration  of  this  question  given  by  Miolatiina  publication  on  the  Affinity  Constants  of 
Acids.  That  different  acids  possess  different  strengths  follows,  for  example,  from  the  pheno- 
menon of  displacement  of  one  acid  from  its  salts  by  another  acid.  When  sulphuric  acid  is  added 
to  a  solution  of  sodium  acetate,  the  characteristic  odour  of  acetic  acid  is  perceived,  since  the 
sulphuric  acid  is  transformed  into  sodium  sulphate  and  a  certain  amount  of  acetic  acid  is  liberated. 
This  quantity  and,  in  general,  the  quantity  of  any  acid  displaced  by  a  second  acid,  is  not  equivalent 
to  the  amount  of  the  latter  added,  but  the  two  acids  divide  the  base  according  to  their  strengths, 
i.  e.,  according  to  their  affinity  constants,  and  also  to  their  quantities.  The  effect  of  the  latter 
factor  may  be  eliminated  by  using  equivalent  quantities  of  the  two  acids  and  of  the  base,  e.  g., 

VOL.  n.  21 


322 


ORGANIC    CHEMISTRY 


resistant  to  oxidising  agents)  with'  concentrated  sulphuric  acid,  CO2  is  evolved, 
whilst  acids  with  carboxyl  united  to  a  tertiary  carbon  atom  (e.  g.,  formic  or 

by  causing  an  equivalent  of  an  acid  to  act  on  an  equivalent  of  neutral  salt,  so  that  the  distribution 
of  the  base  between  the  two  acids  depends  only  on  their  strengths.  A  chemical  equilibrium  is 
then  established  which  is  represented  by  the  equation  : 


(1  -  x)[NaX  +  HX'] 


HX]. 


In  order  that  this  method  may  give  exact  results,  it  is  of  course  necessary  that  the  bodies 
formed  in  the  conditions  of  the  experiment  be  not  eliminated  as  either  gas,  or  solid,  or  complex 
molecules,  etc.,  but  that  they  remain  to  take  part  in  the  equilibrium.  To  determine  this,  Thomsen 
made  use  of  the  thermal  change  and  Ostwald  of  the  changes  of  volume  and  the  indices  of  refraction, 
these  methods  leading  to  the  same  results.  In  general,  any  physical  property  may  be  used  for 
the  analysis  of  the  equilibrated  system. 

If,  for  example,  a  is  the  heat-change  observed  on  neutralising  an  equivalent  of  the  first  acid 
with  a  base,  b  the  corresponding  quantity  for  the  second  acid,  and  c  that  observed  on  adding 
an  equivalent  of  base  to  an  equivalent  of  the  mixed  acids,  it  is  evident  that  c  will  be  equal  to 
the  thermal  effect  of  the  neutralisation  of  a  certain  fraction  of  an  equivalent  of  the  first  acid 
(1  —  a;)  plus  the  thermal  effect  of  the  neutralisation  of  the  complementary  fraction  of  the  second 
acid  : 

a\  T.  ^  ^  it  \  ^    -    & 

-x)a  +  xb;   x  =        r;   t1  -  *)  =      ZT- 


X 

----  ;  is  a  measure  of  the  relative  affinities  of  the  two  acids.    The  following  Table  gives  certain 
(1  —  x) 

values  of  x  determined  by  Ostwald,  x  indicating  the  fraction  of  the  molecule  of  base  taken  up 
by  the  acid  given  first  : 


x 

HNO, 

:  CHC12  •  COOH 

0-76 

H 

HC1 

:  CHC12  •  COOH 

0-74 

H 

CC13- 

COOH 

:  CHC12  •  COOH 

0-71 

CC13- 

COOH 

:  CH2C1  •  COOH 

0-92 

CC1,- 

COOH 

:  H  •  COOH 

0-97 

CI 

COOH  :  CH3  •  COOH 
COOH  :  C2H5  •  COOH 


H  •  COOH  :  C3H7  • 

CH3  •  COOH  :  C3H7  •  COOH  (norm.) 


X 

0-76 
0-79 
0-80 
0-81 
0-53 


If  we  calculate  r  — ,  making  nitric  acid  equal  to  100,  we  obtain  the  following  values  : 

L          *C 


Nitric  acid 
Hydrochloric  acid  . 
Trichloroacetic  acid 
Dichloroacetic  acid 
Monochloroacetic  acid 
Acetic  acid    . 


100 

98 

80 

33 

7 

1-23 


Formic  acid  . 
Propionic  acid 
Butyric  acid 
Glycollic  acid 
Lactic  acid    . 


3-9 

1-04 

0-98 

6-0 

3-3 


The  acids  arrange  themselves  in  the  same  order  and  almost  with  the  same  coefficients,  if 
other  properties  are  studied.  All  acids  possess,  for  example,  the  property  of  accelerating  certain 
hydrolyses,  such  as  that  of  ethyl  acetate  and  the  inversion  of  cane-sugar : 

CH3  •  COOC2H5  +  H20  =  C2HS  •  OH  +  CH3  •  COOH ; 
C12H22On  +  H20  =  2C6H1206. 

In  these  reactions  the  acid  added  acts  only  by  its  presence  (catalysis),  since  at  the  end  of 
the  reaction  it  remains  unchanged.  On  addition  of  equivalent  quantities  of  various  acids,  how- 
ever, the  reactions  take  place  with  greater  or  less  velocities,  i.  e.,  the  same  quantity  of  ethyl 
acetate  or  cane-sugar  is  transformed  in  a  longer  or  shorter  time  according  to  the  acid  added. 
The  velocity  of  the  reaction  is  proportional  to  the  affinity  constant  of  the  acid.  Finally,  the  acids 
are  arranged  in  the  same  order  if  we  compare  their  electrical  conductivities.  According  to  the 
theory  of  electrolytic  dissociation,  the  value  of  the  conductivity  depends  on  the  number  of  mole- 
cules of  the  dissolved  acid  which  are  dissociated  into  their  ions,  i.  e.,  into  hydrogen  ions  on  the 
one  hand,  and  acid  ions  on  the  other.  The  possibility  of  furnishing  hydrogen  ions  in  aqueous 
solution  would  hence  be  characteristic  of  the  acid  nature  of  a  substance,  the  amount  of  these  hydrogen 
ions  in  unit  volume  being  a  measure  of  the  acidity.  With  equivalent  solutions  of  different  acids, 
the  strong  acids  will  be  those  which  contain,  in  a  given  volume  of  the  solution,  a  large  number 
of  hydrogen  ions,  and  the  weak  ones  those  containing  only  a  small  number  of  such  ions. 

The  condition  of  an  acid  in  solution  may  hence  be  represented  by  the  expression  : 


AH 


A'  +  H' 


and  we  may  term  the  fraction  of  the  equivalent  which  is  dissociated,  the  degree  of  dissociation,  a. 
Without  entering  into  further  details  it  may  be  mentioned  that  o  is  related,  besides  to  the  electrical 
conductivity,  also  to  van  't  Hoff's  coefficient  ?',  which  expresses  the  divergence  of  the  osmotic 
behaviour  of  solutions  of  electrolytes  from  the  normal  behaviour  (see  Vol.  L,  p.  102). 

The  degree  of  dissociation  varies  with  the  concentration  of  the  solution  of  the  acid,  increasing 
with  the  dilution  towards  the  limiting  value  1,  which  corresponds  with  complete  dissociation. 


AFFINITY    CONSTANTS 


323 


trimethylacetic  acid)  evolve  CO  and  are  transformed  by  oxidising  agents  into 
hydroxy-acids  :    (CH3)2 :  CH  •  COOH  gives  (CH3)2  :  C(OH)  •  COOH. 

This  increase  is  small  for  strong  acids,  i.  e.,  those  which  contain  a  considerable  number  of  hydrogen 
ions  even  in  concentrated  solutions,  but  is  much  greater  for  the  weak  acids. 

v  100  a 


CH,  • COOH 


CH,C1  •  COOH 


CHCL • COOH 


32 
1024 

32 
1024 

32 
1024 


2-38 
12-66 

19-9 
68-7 

70-2 
99-7 


1 

4-22 

1 
3-53 

1 
1-42 


v  indicates  the  number  of  litres  of 
solution  containing  1  gram-mol.  of 
the  acid. 


The  affinity  constants  given  above  hence  depend  on  the  concentration  of  the  acid,  since  with 
this  the  concentration  of  the  hydrogen  ions  —  on  which  the  value  of  the  acid  properties  of  a  sub- 
stance depends  —  varies.  An  expression  which  is  independent  of  v  may,  however,  be  found  by 
considering  the  equilibrium  :  HA  ;±  H'  +  A',  as  if  it  were  a  gaseous  equilibrium  and  applying 
the  law  of  mass  action  to  it.  If  a  is  the  fraction  of  the  equivalent  which  is  dissociated,  (1  —  o) 
will  be  that  of  the  non-dissociated  part;  and,  if  vis  the  number  of  litres  in  which  the  gram  -equiva- 

lent is  dissolved,     will  be  the.so-called  active  mass  of  the  ions,  i.  e.,  the  number  of  ions  contained 


in  unit  volume,  and 


the  number  of  undissociated  molecules  in  the  same  unit  volume. 


The  law  of  mass  action  gives  : 


-(l-a)t>' 

where  k  is  a  constant  depending  solely  on  the  nature  of  the  equilibrium — that  is,  on  the  nature 
of  the  reacting  bodies — and  on  the  temperature ;  k  is  hence  a  measure  of  the  tendency  of  an  acid 
to  dissociate  and  is  called  the  affinity  constant. 

The  following  Table  gives  the  numbers  referring  to  acetic  acid  and  two  of  its  chloro-derivatives  : 


Acetic  Acid 

Monochloroacetic  acid 

Dichloroacetic  acid 

A 

100  a 

10"  * 

A 

100  a 

10»A 

A 

100  a 

10»A 

16 

6-5 

1-67 

1-79 

56-6 

14-6 

155 

_ 

_' 

_ 

32 

9-2 

2-38 

1-82 

77-2 

19-9 

155 

269-8 

70-2 

5170 

64 

12-9 

3-33 

1-79 

103-2 

26-7 

152 

309-9 

80-5 

5200 

128 

18-1 

4-68 

1-79 

136-1 

35-2 

150 

338-4 

88-0 

5040 

256 

25-4 

6-56 

1-80 

174-8 

45-2 

146 

359-2 

93-4 

5160 

512 

34-3 

9-14 

1-80 

219-4 

56-8 

146 

375-4 

97-6 

— 

1024 

49-0 

12-66 

1-77 

265-7 

68-7 

147 

383-8 

99-7 

— 

In  this  Table  A  denotes  the  molecular  conductivity  corresponding  with  the  dilution  v,  100  a 
the  extent  of  dissociation  in  per  cent.,  and  105  Jc  the  affinity  constant  multiplied  by  100,000. 

This  affinity  constant  has  a  markedly  constitutive  character ;  it  increases,  for  instance,  if  a 
substituent  of  negative  nature,  such  as  OH.  Cl,  N,  N02,  etc.,  enters  a  molecule  and  decreases  if 
positive  groups  such  as  NH2  enter.  The  following  examples  may  be  given  : 

Formic  acid        .         .         . , k  =  127-0 . 10  - B 

Acetic  acid          .         .         .  '       .         .         .         .         .         .         .  1-8 . 10  - 5 

Propionic  acid .         .          .  1-3 . 10  ~ 5 

Substitution  with  halogens  and  similar  groups. 

Monochloroacetic  acid  .         .         .         .         .         .         .         .     &=     155.10"5 

Dichloroacetic  =  5100. 10  ~5 

Trichloroacetic  about  120,000  . 10  - 5 

Eromoacetic 138. 10  ~5 

Cyanoacetic  370. 10  ~5 

Thiocyanoacetic  260. 10  ~5 

/3-Iodopropionic  ........  9-0.10"5 

Substitution  by  hydroxyl. 

Glycollic  acid,  OH  •  CH2  •  COOH k=    15-0. 10  ~5 

Lactic  acid,  CH3  •  CH( OH)  •  COOH 14-0. 10 -5 

£-Hydroxypropionic  acid,  OH  •  CH2  •  CH2  •  COOH  .          .          .  3-1. 10  ~5 

Substitution  by  NHZ. 

a-Aminopropionic  acid  (alanine),  CH3  •  CH(NH2)  •  COOH         .          .     k  =      9-0. 10 ~5 

For  further  examples  and  greater  details,  see  R.  Abegg's  "  The  Electrolytic  Dissociation  Theory." 
New  York,  1907. 


324  ORGANIC    CHEMISTRY 

Separation  of  the  fatty  acids  from  mixtures  of  them  is  not  always  easy,  and 
is  sometimes  effected  by  taking  advantage  of  their  greater  or  less  volatility 
either  in  steam  or  in  a  vacuum,  or  by  precipitating  with  magnesium  acetate 
or  barium  chloride,  since  in  alcoholic  solution  the  higher  acids  are  precipitated 
first.  Use  is  also  made  of  the  fractional  solution  of  the  calcium,  barium,  or 
lead  salts  in  various  solvents  (alcohol,  ether,  etc.),  or  of  fractional  neutralisa- 
tion followed  by  distillation  of  the  acids  not  neutralised.  From  an  aqueous 
mixture  of  formic,  acetic,  butyric,  and  valeric  acids,  the  last  two  may  be  separ- 
ated by  extraction  with  benzene,  from  which  they  may  be  isolated  by  shaking 
with  baryta  water.  Further  separation  may  then  be  effected  as  above. 

Constitution  of  the  Fatty  Acids.  That  these  acids  actually  contain  carboxyl 
groups,  — COOH,  is  indicated  by  the  different  ways  in  which  they  are  formed 
and  decomposed,  but  the  most  characteristic  method  of  preparation  consists 
of  the  hydrolysis  of  the  nitriles,  which  are  obtained  from  the  alkyl  iodides  by 
the  action  of  potassium  cyanide  (see  p.  238).  Two  molecules  of  water  react 
with  one  of  nitrile,  giving  ammonia  and  a  higher  acid  : 

CH3  •  C  i  N  +  2H20  =  NH3  +  CH3  •  COOH. 

The  nitrogen  of  the  nitrile  being  detached,  the  group  —COOH  must  neces- 
sarily be  formed,  since,  from  reasons  already  mentioned,  the  formation  of  a 
group  — C(OH)3  is  excluded,  as  three  free  hydroxyl  groups  cannot  remain 
united  to  one  carbon  atom  (although  the  corresponding  ortho-ethers  are  known 
and  also  acetals,  see  pp.  217,  251  and  252). 

FORMIC  ACID,  H— C/ 

\OH 
Methanoic  Acid 

It  was  shown  as  early  as  the  seventeenth  century  that  ants  contained  a 
special  acid,  which  was  characterised  later  as  formic  acid,  and  was  separated 
(by  distilling  with  water)  from  the  wood  ant,  the  migratory  ant,  bees  (and  hence 
from  crude  honey),  the  hairs  of  the  nettle,  pine  leaves,  perspiration,  urine,  etc. 

Gerhardt  was  the  first,  in  1850,  to  show  that  C02  and  formic  acid  are  obtained  when 
oxalic  acid  is  heated  in  presence  of  sand.  In  1855  Berthelot,  and  later  Lorin  obtained 
good  yields  of  the  acid  in  60  per  cent,  or  even  75  per  cent,  concentration  by  heating  crystal- 
lised oxalic  acid  with  anhydrous  glycerol  in  a  reflux  apparatus ;  this  reaction  yields  first 
CO2,  H20  and  formic  acid  in  the  form  of  glyceride,  HC02[C3H5(OH)2],  this  being  hydrolysed 
by  the  water  of  crystallisation  of  a  further  quantity  of  the  oxalic  acid,  with  regeneration 
of  the  glycerol  and  liberation  of  formic  acid.  For  100  kilos  of  formic  acid,  300  kilos  of 
oxalic  acid  are  consumed.  For  some  years  formic  acid  has  been  more  economically  obtained 
by  decomposing  formates  prepared  synthetically. 

In  1856,  Berthelot  found  that  a  minimal  amount  of  formic  acid  is  obtained  when  CO 
acts  on  concentrated  sodium  hydroxide  solution  at  200°.  Better  yields  were  procured  in 
1880  by  Merz  and  Tibirica  by  the  use  of  powdered  caustic  soda  (as  soda-lime  with  6  per 
cent,  of  moisture)  at  200°.  2><f»*,c 

The  CO  may  be  used  in  the  form  of  producer  gas.  In  1894  Goldschmidt  (Ger.  Pat. 
86,419)  obtained  a  better  yield,  even  at  50°  to  70°,  by  allowing  the  CO  to  act  under  a  pressure 
of  6  to  7  atmos.  on  powdered  caustic  soda,  which  does  not  melt  at  such  temperatures.1 

1  Even  before  purification,  producer  gas  (see  Vol.  I.,  p.  489),  should  contain  about  30  per 
cent,  of  CO,  less  than  1  per  cent,  of  C0.2,  09  per  cent,  of  N,  and  traces  of  sulphur  compounds.  Since 
plants  to  yield  3000  kilos  of  sodium  formate  per  day  are  commonly  employed,  the  theoretical 
requirements  amount  to  1330  kilos  of  CO,  or  about  4000  cu.  metres  of  producer  gas,  obtained  from 
about  800  kilos  of  coke ;  in  practice  use  is  made  of  producers  giving  350  cu.  metres  (i.  e.,  500 
kilos,  consisting  of  130  kilos  of  CO  and  370  kilos  of  N)  of  gas  per  hour  (70  kilos  of  coke),  so 
as  to  allow  for  a  practical  consumption  double  of  the  theoretical.  Owing  to  the  loss  of  CO,  which 
is  poisonous,  during  the  purification  and  manufacturing  operations,  efficient  ventilation  is  neces- 
sary, and  cylinders  of  oxygen  are  kept  for  artificial  respiration  in  cases  of  poisoning.  The  pro- 
ducer has  to  be  in  action  for  three  to  four  hours  before  it  gives  a  gas  of  the  desired  composition, 


325 

The  reaction  is  carried  out  in  horizontal,  cylindrical,  double-walled  autoclaves,  which 
hold  about  2000  litres,  are  about  2  Metres  long  and  1 -^metres  in  diameter,  and  are  con- 
structed of  15  to  18  mm.  sheet-iron,  capable  of  withstanding  internal  pressures  of  10  atmos.  ' 
A  charge  of  2000  kilos  of  caustic  soda  yields  about, 3000  kilos  of  sodium  formate,  three 
autoclaves,  and  a  fourth  one  as  a  spare,  being  required  for  this  amount.  The  heating  lasts 
thirty  hours,  and  six  hours  are  allowed  for  charging  and  discharging.  The  autoclaves  are 
furnished  with  stirrers  to  prevent  the  formation  of  lumps,  the  gas  being  passed  in  slowly. 
For  a  couple  of  hours  the  temperature  is  kept  at  120°  to  130°,  but  the  reaction  then  becomes 
so  vigorous  that  the  steam  is  shut  off  from  the  jacket  of  the  autoclave  (which  withstands 
4  atmos. ),  which  is  then  cooled  to  maintain  the  temperature  constant.  A  suitable  arrange- 
ment of  valves  allows  of  the  exit  of  the  nitrogen,  almost  pure  at  first,  but  rich  in  CO  later. 
The  mass  soon  becomes  pasty,  being  composed  of  a  mixture  of  sodium  formate  and  caustic 
soda,  and  to  prevent  it  from  setting  to  a  very  hard  mass  it  is  essential  that  the  stirrer  is 
kept  in  motion  to  the  very  end  of  the  reaction ;  if  setting  does  occur  it  becomes  necessary 
to  dissolve  the  whole  mass  in  water. 

If  the  producer  gas  contains  even  small  proportions  of  sulphur  compounds  the  mass 
smells  of  mercaptan  and  becomes  red,  the  reaction  remaining  incomplete  and  the  operation 
being  spoiled.  A  successful  operation  yields  a  coarse,  powdery,  yellowish  or  almost  white 
mass,  which  irritates  the  eyes  and  contains  90  to  94  per  cent,  of  formate,  1  to  2  per  cent, 
of  water,  0-1  to  0-7  per  cent,  of  NaOH,  and  2  to  7  per  cent,  of  Na2C03;  the  final  yield  may 
amount  to  95  per  cent,  of  the  theoretical.  Exact  analysis  of  the  product  is  necessary  before 
the  formate  is  transformed  into  formic  acid,  and,  if  carried  out  before  the  mass  is  removed 
from  the  autoclave,  serves  also  to  show  if  the  reaction  between  the  NaOH  and  CO  is 
finished.1 

If  the  formate  is  not  converted  immediately  into  formic  acid,  it  is  stored  in  tightly- 
closed  vessels,  since  otherwise  it  absorbs  moisture  and  forms  very  hard  blocks  showing 
superficial  deliquescence. 

The  sodium  formate  thus  obtained  is  moderately  pure  and  contains  only  sodium  car- 
bonate and  hydroxide  as  impurities.  The  content  of  formate  is  determined  by  titration 
with  permanganate  in  neutral  or  faintly  alkaline  solution. 

Free  formic  acid  containing  85  to  98  per  cept.,  or  even  100  per  cent.,  of  H-C02H  (as 
marketed),  is  obtained  by  decomposing  the  dry  sodium  formate  with  concentrated  sulphuric 
acid  (which,  however,  decomposes  part  of  the  formic  acid  into  CO2  and  H2O,  this  occurring 
slightly  in  the  cold,  but  rapidly  in  the  hot),  and  distilling  off  the  formic  acid.  When  sul- 
phuric acid  of  60°  Be.  is  used  no  such  decomposition  takes  place,  but  less  concentrated  formic 

and  since  it  must  be  cleaned  out  completely  every  eight  hours,  a  gasometer  is  necessary  in  order 
to  prevent  interruption  of  the  working.  The  air  for  use  in  the  producer  should  be  pre-heated 
by  means  of  the  gas  or  of  the  outside  of  the  producer. 

The  gas  should  be  very  carefully  purified  to  remove  ash,  sulphur  compounds  and  carbon 
dioxide  (of  this  not  more  than  0-1  per  cent,  should  remain),  apparatus  similar  to  that  described 
on  p.  50  for  the  purification  of  coal-gas  being  employed.  After  purification  the  gas  is  collected 
in  a  gasometer,  from  which  it  is  drawn  to  the  compressor  to  be  compressed  to  8  atmos.  and  passed 
on  to  the  pressure  reaction  vessels.  Any  gas  unavoidably  escaping  from  the  piping,  cocks  and 
safety  valves  is  passed  into  pipes  which  open  above  the  roof.  Before  compression,  the  gas  is 
passed  through  wood-wool,  which  retains  moisture  and  dust. 

1  According  to  Ger.  Pat.  179,515  the  manufacture  is  carried  out  as  follows  :  The  lump  caustic 
soda,  with  the  natural  moisture  of  about  4  to  5  per  cent.,  is  introduced  into  an  iron  apparatus 
fitted  with  a  stirrer,  a  current  of  CO  being  passed  in,  with  the  initial  temperature  100°  to  120°. 
The  sodium  formate  produced  on  the  surface  of  the  lumps  of  soda  is  detached  in  powder  by  the 
movement  of  the  mass  and  fresh  surfaces  of  caustic  soda  thus  exposed  to  the  action  of  the  CO. 
When  about  two-thirds  of  the  soda  is  transformed  into  formate,  the  powder  of  the  latter  is  col- 
lected into  masses  by  addition  of  water  (about  2  per  cent,  on  -the  weight  of  the  caustic  soda ),  the 
residual  caustic  soda  being  thus  cleaned  and  subsequently  converted  almost  entirely  into  formate. 
In  this  way  the  reaction  becomes  so  rapid  and  energetic  that  cooling,  rather  than  heating,  of  the 
mass  is  rendered  necessary. 

On  the  other  hand,  according  to  Ger.  Pat.  209,417,  caustic  soda  solution  of  20°  Be.  at  150°  to 
170°  is  allowed  to  flow  down  a  tower  filled  with  a  subdividing  material,  a  current  of  producer 
gas  being  passed  upwards.  This  process  gives  continuous  production  of  formate  solution  (if 
a  battery  of  towers  in  series  is  used),  the  residual  nitrogen,  almost  devoid  of  CO,  issuing  at  about 
170° ;  as  this  gas  is  saturated  with  water- vapour,  the  water  withdrawn  from  the  solution  is  gradu- 
ally replaced  in  order  to  maintain  the  concentration  best  adapted  for  the  absorption  of  CO  and 
for  preventing  the  formation  of  incrustations.  Alternatively,  gas  previously  compressed  and 
mixed  with  the  required  amount  of  steam  is  passed  into  the  caustic  soda.  Calcium  formate 
may  be  obtained  by  the  action  of  milk  of  lime  on  coke  at  250°. 


326  ORGANIC    CHEMISTRY 

acid  (60  to  65  per  cent.,  this  being  inapplicable  to  certain  condensation  reactions  and  trouble- 
some to  transport)  results ;  it  is  not  possible  to  obtain  the  concentrated  acid  by  fractional  dis- 
tillation of  the  more  dilute,  since  when  a  concentration  of  70  to  75  per  cent,  is  reached,  water 
and  acid  distil  together  in  constant  proportions  (see  later).  To  prevent  decomposition  by 
concentrated  sulphuric  acid  Hamel  (Ger.  Pat.  169,730)  allows  sulphuric  acid  of  66°  B6.  (75 
kilos  per  100  kilos  of  the  formate)  to  run,  slowly  and  with  cooling,  into  the  formate  dissolved 
in  its  own  weight  of  90  per  cent,  formic  acid ;  to  the  mass  may  be  added  alternately  several 
successive  quantities  of  75  kilos  of  sulphuric  acid  and  100  kilos  of  the  formate,  this  procedure 
being  continued  until  the  vessel  is  filled.  From  the  stirred  mixture  normal  sodium  sulphate 
separates.1  The  decanted  liquid  mass  is  distilled  from  copper  vessels  and  condensed  in 
earthenware  coils  or  receivers.  In  this  way  90  per  cent,  formic  acid  is  produced,  but  100 
per  cent,  acid  may  be  obtained  if  98  to  100  per  cent,  formic  acid  and  monohydrate  or  slightly 
fuming  sulphuric  acid  is  used  for  the  initial  mixture.  Almost  anhydrous  acid  may  be 
obtained  also  by  distilling  the  90  per  cent,  acid  over  anhydrous  copper  sulphate  (3:1) 
(Ger.  Pat.  230,171,  1909). 

Hempel  (Ger.  Pat.  247,490)  proposes  to  treat  the  crude  formate  immediately  it  is 
removed  from  the  autoclave  in  which  it  is  prepared  (but  after  complete  drying  in  a  vacuum 
in  the  autoclave  itself) ;  it  is  discharged,  after  cooling,  into  a  vessel  into  which  a  jet  of  finely 
disintegrated  sulphuric  acid  is  passed,  the  mass  being  intimately  mixed.  A  little  formic 
acid  is  previously  added  to  the  crude  formate  to  neutralise.the  small  amounts  of  free  alkalies 
present.  This  process  is  the  most  economical  and  if  properly  conducted  gives  moderately 
good  yields. 

Formic  acid  from  the  first  distillation  contains  minimal  proportions  of  dissolved  sulphate, 
HC1  and  S,  but  serves  for  almost  all  practical  uses.  It  is  obtained  purer  by  redistilling 
it,  and  if  a  rectifying  column  is  employed,  100  per  cent,  acid  may  be  obtained  even  from 
90  per  cent,  acid,  the  residue  remaining  then  consisting  of  75  per  cent,  acid  (which  distils 
unaltered  unless  mixed  with  dehydrating  agents,  such  as  concentrated  sulphuric  acid, 
anhydrous  copper  sulphate  or  oxalic  acid,  etc.,  the  losses  being  then  considerable). 

The  acid  may  be  titrated  with  caustic  soda  solution  in  presence  of  phenolphthalein. 

Pure  formic  acid  is  a  colourless  liquid  with  a  pungent  odour,  sp.  gr.  1*223 
at  0°  or  T2213  at  20° ;  it  solidifies  on  cooling  and  then  melts  at  8'3°,  and  boils 
at  100'6°  at  760  mm.  or  at  30°  at  50  mm.  pressure.  If  poured  on  the  hand  it 
produces  very  painful  blisters.  In  water  it  is  twelve  times  as  highly  dissociated 
as  acetic  acid,  and  is  hence  a  strong  acid ;  it  dissolves  well  also  in  alcohol  and 
ether.  In  aqueous  solution,  when  the  concentration  reaches  77*31  per  cent., 
corresponding  with  the  composition,  4H  •  CO2H  -{-  3H20,  a  mixture  of  constant 
composition  distils,  as  is  the  case  with  hydrochloric  acid  (Vol.  L,  p.  166);  at 
ordinary  pressure  this  mixture  boils  at  107°.  Unlike  its  homologues  (acetic, 
butyric  acid,  etc.),  it  is  readily  oxidised  by  permanganate,  etc.,  forming  CO2 
and  H20 ;  hence  its  great  reducing  power,  owing  to  which,  in  the  hot,  it  separates 
silver  from  silver  salts,  and  first  mercurous  chloride,  and  then  mercury  from 
mercuric  chloride  solutions.  Thus  it  behaves  as  an  aldehyde,  the  characteristic 

7° 
group  of  which,  —  C\      it  does  indeed  contain.     When  heated  in  a  sealed  tube 

XH 

at  160°  or  treated  with  concentrated  sulphuric  acid,  it  decomposes  readily 
and  completely  into  CO  +  H20.  Finely  divided  rhodium,  ruthenium,  or 

1  Maquenne  proposed  the  addition  of  100  per  cent,  sulphuric  acid  to  85  per  cent,  formic  acid 
in  such  quantity  as  to  form  H2S04  -f-  H20,  the  mass  being  well  cooled  meanwhile ;  this  mixture 
is  thoroughly  mixed  with  the  formate,  and  the  formic  acid  then  distilled.  This  process  permits 
of  the  decomposition  of  unlimited  quantities  of  formate,  and  not  merely  of  that  soluble  in  formic 
acid. 

According  to  Ger.  Pats.  182,776  and  193,509  the  decomposition  may  be  effected  also  by  sodium 
bisulphate,  200  parts  of  the  latter  (well  powdered)  being  mixed  with  100  parts  of  the 'formate, 
and  the  formic  acid  distilled  from  a  still  provided  with  a  stirrer;  the  residue  consists  of  sodium 
sulphate.  This  process  and  the  previous  one  have  not  given  satisfactory  results  in  practice. 

Formates  may  be  decomposed  also  by  hydrofluoric  acid  (Ger.  Pat.  209,418,  1907),  or  by  phos- 
phoric acid  at  temperatures  below  145°  [U.S.  Pats.  970,145  of  1910  (Walker)  and  975,  151]. 


USESOFFORMICACID  327 

indium  (but  not  platinum  or  palladium)  decomposes  it  partially  in  the  cold 
and  completely  at  200°  to  300°  into  C02  and  H2;  under  certain  conditions 
it  yields  a  small  proportion  of  aldehyde,  but  not  in  sufficient  quantity  to  be 
of  practical  importance.  Various  bacteria  produce  the  same  change.  The 
vapour  of  formic  acid  is  inflammable  and  chars  paper ;  with  air  it  may  yield 
detonating  mixtures,  so  that  the  factories  must  be  well  ventilated  and  lighted 
by  electricity. 

USES  OF  FORMIC  ACID.  As  formates  it  is  largely  used  for  making  oxalic  acid,  while 
enormous  amounts  of  free  formic  acid  are  used  in  85  to  90  per  cent,  concentration  1  in  the 
dyeing  industry,  since,  owing  to  its  low  molecular  weight,  it?  competes  with  acetic  acid,  a 
less  quantity  being  required  to  give  a  certain  acidity. 

On  account  of  its  acid  character  and  its  reducing  and  antiseptic  properties,  it  is 
used  as  an  antiseptic  in  wine-making  and  brewing;  it  is  also  employed  to  increase 
the  yield  of  alcoholic  fermentations,  where  it  can  replace  lactic  acid  (not  always 
advantageously ). 

Besides  in  the  dyeing  of  wool,  silk  and  woollen  and  cotton  fabrics  (as  it  does  not  attack 
them),  it  is  used  with  advantage  to  replace  oxalic  acid,  lactic  acid  and  cream  of  tartar  in 
mordanting  wool,  since  it  reduces  chromic  acid  more  slowly  and  more  completely, 
exhausting  the  baths  and  thus  economising  dichromate  (1-5  per  cent,  in  place  of  3  per  cent. ) ; 
in  presence  of  formic  acid  wool  is  dyed  more  uniformly  than  with  acetic  acid.  In  the  tan- 
ning industry  it  serves  well  to  eliminate  lime  even  from  the  most  delicate  hides,  calcium 
formate  dissolving  well  in  water. 

Its  use  in  large  quantities  has  been  anticipated  for  making  cellulose  formate 
or  formylcellulose,  which  in  some  cases  may  replace  cellulose  acetate  (Ger.  Pat. 
189,837),  and  to  prepare  formic  ester  of  glycerol  (diformin)  as  a  substitute  for  acetin 
(Ger.  Pat.  199,873).  It  may  be  used  also  for  making  allyl  alcohol  by  heating  it  with 
glycerol. 

STATISTICS  AND  PRICES.  Before  the  European  War  the  price  for  commercial 
25  per  cent,  formic  acid  (sp.  gr.  1-064),  was  £12  per  ton;  for  50  per  cent.  (1-124),  £22 ;  for 
75  per  cent.  (1-170),  £31 ;  for  85  per  cent.  (1-190),  £36;  and  for  96  to  98  per  cent.  (1-217), 
£54.  The  chemically  pure  acid  at  the  same  concentrations  cost  more  than  double. 

For  large  contracts  the  commercial  90  per  cent,  acid  fell  in  price  in  1913  to  £22  to  £24 
per  ton,  and  competed  keenly  with  acetic  acid,  which  was  largely  replaced,  especially  in 
France,  in  the  dyeing  of  wool  and  silk. 

In  1913  the  German  output,  from  six  factories,  was  estimated  at  5000  tons ;  in  Russia 
there  were  three  factories,  in  Switzerland  two,  in  France  two,  and  one  each  in  England, 
the  United  States,  Holland  and  Austria.  Early  in  1920  the  Societa  Italiana  Prodotti 
Esplodenti  started  a  factory  at  Cengio. 

Presence  of  hydrochloric  acid  as  impurity  may  be  detected  by  dilution  (1 :  20)  and 
addition  of  silver  nitrate  :  oxalic  acid  may  be  detected  by  neutralising  with  ammonia  and 
adding  calcium  chloride.  If  no  acroleiin  or  allyl  alcohol  is  present,  it  does  not  give  a  pungent 
odour  after  neutralisation  with  caustic  soda. 

SALTS  OF  FORMIC  ACID  are  called  formates  and  are  generally  soluble  in  water  and 
crystallisable ;  almost  all  the  characteristic  properties  and  reactions  of  formic  acid  (reduc- 
tion, etc. )  are  shown  also  by  its  salts.  With  concentrated  sulphuric  acid  in  the  hot,  they 
yield  carbon  monoxide.  Formates  are  obtained  by  the  action  of  carbon  monoxide  on 

1  Its  strength  is  determined  by  means  of  standard  sodium  hydroxide  solutions,  using  phenol- 
phthalein  as  indicator,  but  when  other  acids  are  also  present  it  is  titrated  with  permanganate 
in  alkaline  solution  or  with  chromic  acid  in  acid  solution.  The  CO  evolved  when  it  is  treated 
with  concentrated  sulphuric  acid  may  also  be  measured.  When  other  organic  acids  are  present, 
the  dilute  mixture  is  treated  with  mercuric  acetate  at  the  boiling  temperature,  the  mercurous 
acetate  which  separates  being  filtered  off  in  the  cold  and  dissolved  in  nitric  acid,  the  calomel 
precipitated  with  sodium  chloride  then  being  weighed.  Alternatively,  dilute  formic  acid  solution 
(0-2  gram  per  litre)  may  be  treated  with  about  15  times  the  weight  of  mercuric  chloride  (calculated 
on  the  acid)  dissolved  in  200  c.c.  of  hot  water,  the  liquid  being  well  shaken  and  the  mercurous 
chloride  precipitate,  after  treatment  with  caustic  soda,  collected  on  a  Gooch  crucible,  washed, 
dried,  and  weighed ;  multiplication  of  the  weight  by  0-097726  gives  the  weight  of  formic  acid 
(Franzen  and  Greve,  1909).  Formic  acid  may  be  detected,  even  in  presence  of  aldehydes,  acetic 
acid,  and  methyl  alcohol,  by  means  of  sodium  bisulphite  solution,  which  gives  a  reddish -yellow 
coloration. 


328  ORGANIC    CHEMISTRY 

metallic  hydroxides  in  the  hot  and  under  pressure  (see  also  Fr.  Pat.  382,001,  1907,  and 
U.S.  Pat.  875,055, 1 907 ).  When  heated  at  200°  to  400°,  the  alkali  formates  yield  carbonates 
and  oxalates  and  chemically  pure  hydrogen.  Potassium  formate,  H-COOK,  forms  deli- 
quescent crystals,  m.-pt.  150°.  Sodium  formate,  H  •  COONa,  crystallises  well  with  SHgO 
at  0°  or  with  2H20  at  17°,  and  the  anhydrous  salt  melts  at  200°  (the  pure  salt  costs  3s.  Id. 
per  kilo,  and  the  commercial  salt  Is.  Id.).  Ammonium  formate,  H  •  COONH4,  melts  at 
115°  and  at  a  higher  temperature  decomposes  into  formamide,  water,  and  a  little  hydro- 
cyanic acid ;  since,  in  its  decomposition  when  heated,  it  gives  nitrogen  and  carbon  com- 
pounds, it  is  used  to  harden  and  cement  steel  (the  pure  salt  costs  as  much  as  9s.  Qd.  per  kilo ). 
The  magnesium,  barium,  and  calcium  gaits  are  also  soluble  in  water;  the  last  costs  4s. 
(pure)  or  2s.  (impure)  per  kilo.  Lead  formate,  (H  •  COO)2Pb,  dissolves  only  slightly  in  cold 
water,  but  readily  in  hot,  and  hence  serves  well  to  separate  formic  from  other  acids.  Acid 
formates,  such  as  H '  COONa  -f-  H  •  COOH,  are  also  known.  Silver  formate  is  insoluble 
in  water. 

ETHYL  FORMATE,  H  •  C02C2H5,  is  a  colourless,  volatile,  inflammable  liquid,  sp.  gr. 
0-948,  b.-pt.  54-4°.  It  is  obtained  by  heating  in  a  reflux  apparatus  for  ten  hours  at  80°, 
and  stirring  continually  a  mixture  of  2  parts  of  alcohol,  3  parts  of  sodium  formate,  and  10 
parts  of  powdered  sodium  bisulphite,  the  ester  being  finally  distilled.  It  has  the  odour  of 
arrack,  and  is  used  as  artificial  essence  of  rum  and  also  in  the  treatment  of  laryngitis  and 
acute  catarrh. 

The  methyl  ester  boils  at  32-3°  and  is  used  as  a  solvent  for  acetylcellulose. 

ACETIC  ACID,  CH3  .  C/ 

XOH 
Ethanoic  Acid 

Although  its  constitution  was  first  determined  by  Berzelius  in  1814,  acetic 
acid  has  been  known  from  the  earliest  times,  since  it  forms  easily  in  wine 
(vinegar),  in  many  vegetable  juices,  in  sour  milk,  in  perspiration,  in  excreta, 
etc.  In  1700  Stahl  obtained  it  in  a  concentrated  form  by  freezing  the  dilute 
acetic  acid,  then  neutralising  with  alkali  and  distilling  the  acetic  acid  after 
addition  of  sulphuric  acid.  It  is  often  formed  in  the  oxidation  and  combustion 
of  many  organic  substances ;  of  the  various  synthetic  processes  for  its  prepara- 
tion, that  of  Kolbe  (1843)  may  be  mentioned  :  perchlorethane,  in  presence  of 
water  and  under  the  influence  of  light,  gives  trichloroacetic  acid  :  CC13  *  CC13  -f- 
2H20  =  3HC1  +  CC13  •  COOH,  and  this  is  reduced  by  nascent  hydrogen  to 
acetic  acid.  Commercially  it  is  obtained  from  ethyl  alcohol  and  especially 
by  the  dry  distillation  of  wood  (see  later). 

PROPERTIES.  When  pure,  acetic  acid  forms  a  colourless  liquid  of  sp.  gr. 
1-0553  at  15°  and  specific  heat  0'522  between  26°  and  96°;  it  solidifies 
at  +16'7°in  white  crystals  (hence  the  name  glacial  acetic  acid),  which  are  very 
hygroscopic  and  have  the  sp.  gr.  1'08  at  0°;  it  boils  at  118°,  but  evaporates 
considerably  below  this  temperature  owing  to  its  high  vapour  pressure.  It  is 
soluble  in  all  proportions  in  water,  alcohol,  and  ether.  It  is  one  of  the  strongest 
organic  acids  and  dissolves  calcium  carbonate  with  evolution  of  carbon  dioxide. 
Its  vapours  burn  with  a  bluish  flame.  It  dissolves  many  organic  and  several 
inorganic  substances  (P,  S,  HC1,  Fe,  Al,  etc.).1.  When  pure  concentrated  acetic 
acid  is  mixed  with  water,  heating  and  contraction  take  place ;  the  specific  gravity 
increases  on  dilution  of  the  pure  acid  and  reaches  a  maximum  (1'0748)  with  77 
per  cent,  of  the  acid  (corresponding  with  the  hydrate,  C2H402  +  H20),  after - 

1  Acetic  acid  readily  attacks  the  common  metals,  especially  iron,  but  if  the  latter  is  in  the 
form  of  siliceous  cast-iron  containing  about  14  per  cent,  of  silicon  and  0-9  per  cent,  of  carbon 
(as  in  tantiron,  ironac,  and  hdianite),  it  is  moderately  resistant.  Pure  silver  withstands  the  action 
of  the  acid  well,  and  copper  is  only  slightly  attacked  if  it  is  kept  shiny  and  unoxidised.  Plant 
used  in  working  with  acetic  acid  is  often  of  stoneware,  which  stands  weil  if  not  exposed  to  con- 
siderable and  rapid  changes  of  temperature;  quartz  apparatus  is  able  to  withstand  also  such 
temperature  changes  (see  Vol.  L,  pp.  501,  741). 


ACETIC    ACID 


329 


wards  diminishing  gradually  as  the  dilution  increases.1  Hence  when  the  density 
of  an  acetic  acid  solution  is  given  it  must  be  indicated  whether  it  refers  to  solu- 
tions containing  more  or  less  than  77  per  cent,  of  the  acid.  It  cannot,  however, 
be  assumed  that  a  chemical  compound,  C2H402  -f-  H2O,  actually  corresponds 
with  the  maximum  density  of  the  aqueous  solution,  since  at  other  temperatures 
the  maximum  densities  correspond  with  different  compositions;  thus,  at  0° 
the  maximum  density  is  obtained  with  80  per  cent,  of  acetic  acid  and  at  40° 
with  75  per  cent.  The  strength  of  acetic  acid  generally  refers  to  the  weight  and 
not  to  the  volume  of  the  acid. 

The  lowest  freezing-point  is  obtained  (—27°)  with  the  aqueous  solution 
containing  60  per  cent,  of  the  acid  (corresponding  with  a  hydrate,  C2H4O2  + 
2H20),  whilst  solutions  with  84  per  cent,  and  with  10  per  cent,  freeze  at  — 3'2°. 
Unlike  those  of  formic  acid  and  of  mineral  acids,  aqueous  solutions  of  acetic 
acid  yield  no  distillate  of  constant  composition. 

The  vapour  density  of  the  acid  indicates  a  mixture  of  simple  and  double 
molecules  below  250°,  and  simple  molecules  alone  above  this  temperature. 
With  hydrogen  bromide  it  forms  reddish  crystalline  additive  products,  e.  g., 
CH3  •  COOH,  Br2,  4HBr.  Certain  bacteria  decompose  it  into  CH4  -f  CO2. 

In  contact  with  red-hot  pumice,  acetic  acid  vapour  only  partially  decom- 
poses, giving  acetone,  C02,  and  a  little  phenol  and  benzene.  Chlorine  replaces 
first  one  atom  and  then  three  atoms  of  hydrogen  in  the  CH3  group ;  bromine 
acts  similarly  at  120°,  but  iodine  does  not  react.  It  resists  in  the  cold  the  action 
of  chromic  acid  or  permanganate,  but  when  heated  with  the  latter  forms  CO?, ; 
it  is  very  resistant  to  the  action  of  reducing  agents  (sodium  amalgam,  etc.). 
The  heat  of  combustion  is  3700  Cals.  (for  1  kilo). 

MANUFACTURE  OF  ACETIC  ACID.  The  most  important  prime  material  for  the 
manufacture  of  crude  acetic  acid— from  which  salts  are  obtained  for  the  preparation  of 
the  pure  acid — is  wood,2  alcohol  (from  cereals  and  wine)  being  only  rarely  used.  During 

1  Oudeman's  Table  :  specific  gravity  and  concentration  of  acetic  acid  at  15°. 


Specific 
gravity 

Per  cent, 
of  acid 
by  weight 

Specific 
gravity 

Per  cent, 
of  acid 
by  weight 

Specific 
gravity 

Per  cent, 
of  acid 
by  weight 

Specific 
gravity 

Per  cent, 
of  acid 
by  weight 

Specific 
gravity 

Per  cent, 
of  acid 
by  weight 

1-0007 

1            1-0185 

13 

1-0412 

30 

1-0646 

54 

1-0748 

78 

1-0014 

v  1-5         1-0192 

13-5 

1-0424 

31 

1-0653 

55 

1-0748 

79 

1-0022 

2            1-0200 

14 

1-0436 

32 

1-0660 

56 

1-0748 

80 

1-0030 

2-5         1-0207 

14-5 

1-0447 

33 

1-0666 

57 

1-0747 

81 

1-0037 

3 

1-0214        15 

1  0459 

34 

1-0673 

58 

1-0746 

82 

1-0045 

3-5         1-0221 

15-5 

10470 

35 

1-0679 

59 

1-0744 

83 

1-0052 

4            1-0228 

16 

1-0481 

36 

1-0685 

60 

1-0742 

84 

1-0000 

4-5 

1-0235 

16-5 

1-0492 

37 

1-0691 

61 

1-0739 

85 

1-0067 

5          I  1-0242 

17 

1  05(12 

38 

1-0697 

62 

1-0736 

86 

1-0075 

5-5 

1-0249 

17-5 

10513 

39 

1-0702 

63 

1-0731 

87 

1-0083 

6 

1-0256 

18 

1-0523 

40 

1-0707 

64 

1-0726 

88 

1-0090 

6-5 

1-0263 

18-5 

1-0533 

41 

1-0712 

65 

1-0720 

89 

1-0098 

7 

1-0270 

19 

1-0543 

42 

1-0717 

66 

1-0713 

90 

1-0105 

7-5 

1-0277 

19-5 

1-0552 

43 

1-0721 

67 

1-0705 

91 

1-0113 

8            1-0284        20 

1-0562        44 

1-0725 

68 

1-0696 

92 

1-0120 

8-5         1-0298        21 

1-0571        45 

1-0729 

69 

1-0686 

93 

1-0127 

9            1-0311        22           1-0580 

46 

1-0733 

70 

1-0674 

94 

1-0135 

9-5 

1-0324        23           1-0589        47 

1-0737 

71          1-0660 

95 

1-0142 

10            1-0337        24           1-0598        48 

1-0740 

72       ii  1-0644 

96 

1-0150 

10-5         1-0350 

25           1-0607        49 

1-0742 

73           1-0625 

97 

1-0157 

11            1-0363        26           1-0615 

50 

1-0744 

74 

1-0604 

98 

1-0164 

11-5         1-0375        27           1-0623  j       51 

1-0746 

75 

1-0580 

99 

1-0171 

12            1-0388        28           1-0631 

52 

1-0747 

76 

1-0553 

100 

1-0178 

12-5         1-0400  :      29           1-0638        53          1-0748        77 

— 

~~ 

2  The  wood  of  deciduous  trees,  after  being  dried  at  110°,  contains  about  50  per  cent.  C,  6  per 
cent.  H,  and  44  per  cent.  0,  its  calorific  value  being  about  4000  Cals. ;  air-dried  wood,  with  25  per 
cent,  of  moisture,  gives  about  2700  Cals. 

The  chemical  change  occurring  in  the  decomposition  of  wood  subjected  to  distillation  at  the 


330 


ORGANIC    CHEMISTRY 


FIG.  233. 


recent  years  acetic  acid  has  been  manufactured  synthetically  from  acetylene  (see  later :  Acetic 
anhydride)  similarly  to  the  synthesis  of  alcohol  (q.v.). 

Dry  Distillation  of  Wood.     It  has  been  already  mentioned  (see  p.  38)  that  Lebon  in 

1799  patented  a  process  of 
dry  distillation  of  wood  for 
producing  illuminating  gas 
and  on  p.  128,  in  dealing 
with  the  manufacture  of 
methyl  alcohol — also  a  pro- 
duct of  the  dry  distillation 
of  wood — the  separation  of 
the  crude  products  of  this 
distillation  was  described. 
A  description  will  now  be 
given  of  the  apparatus  used 
in  this  industry.  It  is  not  necessary  to  consider  the  primitive  furnaces  formerly  used, 
which  gave  a  minimal  yield  and  a  slow  and  incomplete  carbonisation,  or  the  vertical 
retorts  used  in  the  early  days  of  the  industry,  although  these  are  again  in  use  nowadays, 
but  in  a  far  more  rational  manner.  These  first  vertical 
retorts  were  followed  by  horizontal  ones,  which  are 
still  used  in  many  factories. 

These  are  formed  of  sheet  iron  (10  to  12  mm.  thick) 
and  are  about  1  metre  in  diameter  and  3  metres  in 
length;  they  are  arranged  in  pairs  in  furnaces  (Figs. 
233,  234),  with  suitable  flues  for  the  hot  gases,  and 
they  can  be  charged  and  discharged  by  means  of  a 
cover  hinged  at  the  back,  although  not  very  con- 
veniently. On  this  account,  and  also  in  order  to 
obtain  continuous  working,  and  hence  more  efficient 
utilisation  of  the  heat  of  the  furnaces,  use  is  again  being  largely  made  of  vertical  retorts, 
which  can  be  removed  from  the  furnace  at  the  end  of  the  operation,  to  be  replaced 
immediately  by  other  retorts  already  charged.  In  Fig.  235,  on  the  left,  is  seen  the 


FIG.  235. 


ordinary  pressure  is  represented  by  Klason  (1914)  by  the  following  hypothetical  equation,  minimal 
empirical  formulae  being  ascribed  to  the  wood,  charcoal  and  tar,  which  are  in  good  agreement 
with  the  elementary  compositions  of  these  products  : 


2C42H56028  =  2C16H1002 

Wood.  Charcoal 


26H20  +  5C02  +  SCO  +  2CH3  •  C02H  +  CH3 


OH  +  C23H1804. 

Tar 


Under  practical  conditions,  however,  less  charcoal,  less  water  and  more  gas  are  obtained 
than  this  equation  indicates.  Air-dried  beech,  containing  25  per  cent,  of  moisture,  yields  on 
the  average  :  26  per  cent,  of  dry  charcoal,  5  per  cent,  of  acetic  acid,  1-5  per  cent,  of  methyl  alcohol, 
8  to  9  per  cent,  of  tar,  38  per  cent,  of  water  (25  per  cent,  from  the  moisture  and  13  per  cent,  from 
the  cellulose,  etc.,  decomposed),  and  20  per  cent,  of  gas  (i.  e.,  about  12  cu.  metres  per  100  kilos 
of  wood). 


DISTILLATION    OF    WOOD 


331 


arrangement  of  a  battery  of  these  retorts,  with  a  trolley  and  crane  H  for  raising  and 

transporting  the  charged  retorts,  which  are  then  emptied  into  the  charcoal  stove  by 

means  of  the  tipping  trolley,  K.     The  right-hand  side  of  the  figure  shows  in  detail 

the  upper  part  of  a  retort  charged  with  wood.     The  capacity  of  each  retort  is  about 

4  cu.  metres  or  1500  kilos  of  wood;    the  smaller  pieces  are  placed  at  the  bottom, 

the  medium-sized  ones  next,  and  the  largest  ones  at  the  top.     In  order  that  the  retorts 

may  not  be  worn  out  too  rapidly  by  the  external  heat,  they  are  smeared  with  a  very  thin 

layer  of  earth  made  into  a 

paste  with  water  and  applied 

with  a  brush.     Every  charge 

of  1500  kilos  requires  600  to 

800  kilos  of  coal  for  heating 

and  distilling.     If  leaks  are 

detected  during  the  heating, 

they  are  closed  with  clay,  and 

it  is  for  this  purpose  that  the 

retorts  project  15  to  20  cm. 

beyond  the  furnace. 

Although  this  arrange- 
ment is  still  largely  used,  it 
necessitates  a  considerable 
amount  of  manual  labour 
and  lifting,  so  that  it  has 
been  proposed  to  incline  the 
retorts  as  in  gas-manufacture 

(see  pp.  4 1,43),  and  to  furnish  j<IQ.  236. 

them  with  apertures  at  the 

top  for  charging  and  others  at  the  bottom  for  automatically  discharging  them.  Fig.  236 
shows  the  section  of  a  battery  of  these  retorts  (A )  of  the  Mathieu  type,  8  giving  the  cross- 
section  of  a  retort.  The  wood  is  charged  automatically  from  the  running  buckets,  c, 
suspended  at  g.  At  the  end  of  the  operation  the  charcoal  is  discharged  below  into  the 
vessel,  P,  which  is  provided  with  a  cover  to  prevent  the  hot  charcoal  from  igniting  in  the 
air.  The  vapours  from  the  distillation  pass  into  the  tube,  H,  which  conducts  them  into  a 
coil  cooled  by  the  water  in  T  and  then  into  the  barrel,  J,  where  the  tar  and  the 

pyroligneous  acid  separate ;  the  gas,  which  does 
not  condense,  but  is  still  partly  combustible,  is 
washed  and  passes  through  the  pipe,  k,  to  be 
burnt  under  the  furnace-hearth,  D;  there  is  no 
danger  of  explosion,  since,  if  there  is  any  air  in 
the  retorts,  it  cannot  communicate  with  the 
hearth,  the  barrel,  J,  serving  as  a  water-seal. 

Of  late  years,  use  has  also  been  made  of 
vertical  retorts  (Fig.  237)  with  an  upper  orifice, 
o,  for  charging,  and  a  lower  one,  e,  for  discharg- 
ing (see  Ger.  Pat.  192,295,  November  15,  1906). 
From  the  hearth,  &,  the  hot  gases  pass  to  the  flues 
surrounding  the  retort  and  thence  at  S  to  the 
shaft ;  the  gases  and  vapours  from  the  wood  issue 
from  the  tube,  n,  and  are  partially  condensed  in 
the  refrigerator,  m.  At  the  end  of  the  distilla- 
tion, the  orifice,  e,  is  opened  and  the  charcoal 

discharged  into  the  covered  waggon,  k,  and  conveyed  to  the  store,  whilst  the  retort,  while 
still  hot,  is  filled  with  a  new  charge  of  wood. 

In  order  to  diminish  labour  and  other  costs,  use  has  been  made  for  some  years  in  the 
United  States  and  in  Sweden  of  very  large  retorts  or  furnaces.  That  shown  in  Fig.  238, 
which  is  most  commonly  used  in  America,  consists  of  a  furnace  with  parallelepipedal 
chambers,  trolleys  entering  at  one  end  charged  with  the  wood  and  leaving  at  the  opposite 
end  with  the  charcoal.  The  distillation  is  continuous  and  in  each  furnace  are  two  retorts 
R.  The  furnace  with  the  flues  which  serve  for  the  circulation  of  the  hot  gases  from  two 


FIG.  237. 


332 


ORGANIC    CHEMISTRY 


opposite  hearths,  F,  or  from  a  single  producer,  and  which  surround  the  rectangular,  thick 
sheet-iron  retorts  or  chambers,  resembles  somewhat  a  metallurgical  coke  furnace  (see 
Vol.  I.,  p.  452).  The  wood  is  loaded  in  large  waggons,  W,  which  run  on  the  rails  s.  The 
vapour  and  gas  leave  the  retort  by  the  tubes  T  connected  with  the  condensers  V,  the  non- 
condensed  gas  passing  through  the  tubes  a  to  the  hearth ;  the  arrows  show  the  course  of 
the  hot  gases  in  the  vertical  flues  surrounding  the  retorts. 

If  the  retorts  are  heated,  not  with  wood  and  charcoal,  but  by  the  gases  produced  with 
hot  air  in  a  regenerator  furnace  (see  Vol.  I.,  pp.  487  and  634),  one-third  of  the  fuel  is  saved.1 
In  small  retorts  every  distillation  occupies  from  eight  to  sixteen  hours,  according  as  the 
wood  is  seasoned  or  not.  It  is  of  considerable  advantage  to  bark  or  split  the  wood  and 
to  season  it  in  piles  for  at  least  a  year,  during  part  of  the  time  protected  from  the  rain ; 
better  still  is  it  if  before  being  charged  into  the  retorts,  the  wood  is  dried  or  heated  by 
the  hot  gases  before  these  pass  to  the  chimney. 


FIG.  238. 


The  yield  of  acetic  acid  and  by-products  varies  widely  with  the  kind  of  wood  and  with 
the  conditions  of  distillation.  Preference  is  usually  given  to  hard  woods  like  oak,  horn- 
beam, and  beech;  of  less  value  are  white  woods,  with  the  exception  of  lime,  which  gives 
good  results ;  the  wood  of  trees  eighteen  to  twenty  years  old,  grown  in  a  dry,  poor  soil  and 

1  That  there  is  marked  scope  for  saving  fuel  is  shown  also  by  the  thermal  balance  derived 
from  the  chemical  equation  given  in  the  note  on  p.  330.  The  reaction  is  exothermic,  the 
theoretical  positive  heat  being  almost  6  per  cent,  of  the  heat  of  combustion  of  the  wood.  Hence, 
with  a  battery  of  furnaces  in  action,  the  amount  of  heat  to  be  supplied  for  the  distillation  should 
be  only  that  necessary  to  heat  each  fresh  charge  of  wood  to  about  250°  (at  which  the  above 
exothermic  reaction  commences )  and  to  evaporate  the  moisture  of  the  wood,  besides  that  carried 
off  by  the  hot  gases  from  the  retorts  and  hearths  and  that  of  the  hot  charcoal  extracted. 

Since  the  non -condensable  gases  from  the  retorts  (100  kilos  of  wood  yield  about  12  cu.  metres 
containing,  on  the  average,  56  per  cent,  of  C02,  34  per  cent,  of  CO,  8  per  cent,  of  CH,j,  and 
2  per  cent,  of  C2H4,  and  furnishing  about  2000  cals.  per  cu.  metre)  are  utilised  for  heating,  and 
since  also  a  good  part  of  the  heat  of  the  hot  gases  from  the  flues  and  of  the  hot  charcoal  may 
be  employed  to  dry  or  warm  the  wood  prior  to  distillation,  the  quantity  of  wood  burnt  to  heat 
the  retorts  should  be  only  about  10  per  cent,  of  that  distilled.  In  most  works,  even  those  using 
seasoned  wood,  however,  this  proportion  is  as  high  as  30  to  35  per  cent.,  and  in  only  few  cases 
is  it  below  20  per  cent. 


333 


cut  in  winter,  is  more  suitable  than  young  wood  or  wood  grown  on  plains  in  a  moist  or 
fertile  soil  and  cut  at  other  seasons  of  the  year.1 

UTILISATION  OF  THE  SAWDUST.  Many  attempts  have  been  made,  not  always 
successfully,  to  utilise  the  various  forms  of  wood  refuse,  especially  the  sawdust.  This 
presents,  however,  considerable  difficulty,  owing  to  the  excessive  moisture,  the  large  volume, 
the  abundance  of  resins  which  char  and  form  incrustations,  and  the  low  thermal  con- 
ductivity, which  prevents 
the  heat  from  reaching  the 
middle  of  the  retort. 

The  problem  has  not 
yet  been  definitely  solved, 
but  the  forms  of  apparatus 
which  up'  to  the  present 
have  given  the  best  results 
are  that  of  Halliday  (1851 ), 
shown  in  Fig.  239,  and  the 
more  recent  one  of  Rolle, 
used  especially  for  distilling 
bituminous  lignites  (see  p. 
334)  and  shown  in  Fig.  240. 
Above  the  Halliday  furnace 
the  moist  material  (saw- 
dust, exhausted  dye  woods, 
etc.)  is  dried  slowly  in  a 
and  slowly  descends  a 
vertical  screw  moved  by  FIG.  239. 

the  cog-wheel,  6,  into  the 

horizontal  iron  cylinder ;  there  the  mass  is  transported  slowly  to  the  opposite  end  by  a 
horizontal  screw  and  falls  in  a  charred  condition  through  the  channel,  d,  into  a  water- 
tank,  where  it  is  extinguished.  The  vapours  and  gases  from  the  distillation  issue  at  e 
and  /  and  pass  to  the  condensing  apparatus.  The  cylinder  is  heated  by  the  hot  fumes 
from  the  fire,  g,  several  cylinders  being  heated  at  the  same  time  in  one  furnace. 

1  The  yields  obtained  from  100  kilos  of  various  kinds  of  wood,  barked  and  subjected  to 
rapid  (E,  about  three  hours)  or  slow  distillation  (S,  more  than  six  hours)  are  given  below  : 


Aqueous  acid  distillate 

Kind  of  Wood 

Tar 

Strength 

Equal  to 

Dry 
charcoal 

Gas 

Total 

of  acetic 
acid 

pure 
acetic 
acid 

Kilos 

Kilos 

Per  cent. 

Kilos 

Kilos 

Kilos. 

Dogwood  (Rliamnus  frangula)  branches  .  8 
Do.          Do  R 

7-58 
5-15 

45-21 
40-23 

13-38 
11-16 

6-05 
4-49 

26-50 
22-53 

20-71 
32-09 

Hornbeam  (Carpinus  bet-idus)  trunk         .  S 
Do.           Do  R 

4-75 
5-55 

47-65 
42-97 

13-50 
12-18 

6-43 
5-23 

25-37 

20-47 

22-23 
31-01 

Alder  (Alniis  glutinosa)  trunk         .          .  S 

6-39 

44-14 

13-08 

5-77 

31-56 

17-91 

Do.          Do  R 

7-06 

40-70 

10-14 

4-13 

21-11 

31-13 

Aspen  (Popvlus  tremula)  trunk       .          .  S 
Do.          Do  R 

6-90 
6-91 

40-54 
39-45 

12-57 
11-04 

5-10 
4-36 

25-47 
21-33 

27-09 
32-31 

Birch  (Betula  alba)  trunk       .          .          .8 

5-46 

45-59 

12-36 

5-63 

29-24 

19-17 

Do.          Do  R    3-24 

39-74 

11-16 

4-43 

21-46 

35-56 

Beech  (Fagus  sylvalica)  trunk         .          .  S     5-85 

39-45 

11-37 

5-21 

26-69 

21-66 

Do.          Do  R  '  4-90 

45-08 

9-78 

3-86 

21-90 

33-75 

Oak  (Quercus  robur)      .         .         .         .  S    3-70 

44-45 

9-18 

4-08 

34-68 

17-17 

Do.          Do  R    3-20 

42-04 

8-19 

3-44       27-73 

27-03 

Austrian  Pine  (Pinuslaricio)  trunk          .  <S     9-30 

42-31 

6-36 

2-69       26-74 

21-65 

Do.          Do  R    5-58 

38-19 

5-40 

2-06 

24-06 

32-17 

Pine  (Finns  obi  en)  trunk        .          .          .  S     5-93 

40-99 

5-61 

2-30 

25-55 

28-11 

Do.          Do  R    6-20 

40-15 

4-44 

1-78 

23-35 

32-80 

A  detailed  study  of  the  distillation  of  chestnut  wood  was  made  by  G.  Borghesani  in  1910. 
The  bark  and  branches  always  give  a  smaller  yield. 


334 


ORGANIC    CHEMISTRY 


The  Bolle  furnace  has  been  applied  in  Germany  on  a  vast  scale  to  the  distillation  of 
brown,  pitchy  lignite  and  allows  of  continuous  working  and  high  output.  It  serves  also 
for  distilling  small  wood  waste. 

The  furnace  (Fig.  240)  is  6  to  7  (or  even  10)  metres  high  and  the  inner  cylindrical 
distillation  chamber  is  about  1-7  metres  in  diameter.  The  outer  masonry  (shown  with 
inclined  shading)  is  of  ordinary  bricks,  while  the  inner  walls  of  the  chamber  and  the  flues 
D  for  the  hot  gases  from  the  hearth  H  are  of  firebrick  (dotted  in  the  figure)  of  distinctly 
basic  character  (so  as  to  prevent  fusion  with  the  basic  ash  carried  over  by  the  gases). 

The  distillation  chamber  must  be  quite  tight  and  the  firebricks  are  fitted  one  into  the 
other  with  a  silicate  or  asbestos  mastic.  Contact  of  the  material  to  be  distilled  with  the 
hot  peripheral  walls  of  the  inner  part  of  the  chamber  is  ensured  by  inserting  a  column  of 


FIG.  240. 

truncated  conical  rings  of  siliceous  cast-iron  or  enamelled  iron,  these  being  superposed 
and  kept  in  position  by  a  central  vertical  rod  joined  by  transverse  rods  to  certain  of  the 
rings ;  the  uppermost  conical  ring  is  provided  with  a  cover.  The  wood  waste  is  charged 
peripherally  at  the  top  and  gradually  chars  as  it  passes  automatically  to  the  bottom,  where 
it  collects  in  the  hopper  F  and  is  discharged  periodically,  by  opening  G,  into  the  iron 
truck  underneath,  this  being  at  once  covered  to  prevent  ignition  of  the  charcoal. 

The  gases  and  vapours  produced  pass  between  the  rings  into  the  inner  space,  from  which 
they  are  drawn  through  the  tubes  A  and  B  to  the  external  condensation  apparatus.  The 
non-condensed  gases  are  led  through  K  to  the  distributor  /  in  the  hearth  H,  where  they  are 
burnt  together  with  charcoal  and  wood,  the  combusted  gases  passing  through  the  flue  R 
to  the  chimney ;  these  non-condensed  gases  are  sent  to  the  hearth  only  when  the  walls  of 
the  furnace  are  already  very  hot,  since  otherwise  they  extinguish  the  fire.  Use  of  the 
gases  in  this  way  saves  more  than  one-half  of  the  fuel,  30  kilos  (instead  of  80  to  100  kilos) 


PYROLIGNEOUSACID  335 

of  the  latter  being  then  sufficient  for  the  distillation  of  100  kilos  of  wood.  With  large 
furnaces  the  heating  may  be  effected  solely  with  gas  (obtained  partly  from  producers). 
These  chamber  retorts  are  15  to  18  metres  in  length  and  contain  four  or  five  trucks,  each 
holding  6  to  8  cu.  metres  of  wood. 

F.  H.  Meyer  obtains  better  results  by  using  two  large  retorts  or  cylinders  set  horizontally 
in  a  furnace.  Into  these  cylinders  run  trolleys  carrying  metal  plates  with  the  sawdust 
spread  out  in  thin  layers.  The  fire  is  started  and  the  first  cylinder  heated  and  distilled 
rapidly,  the  hot  fumes  then  going  to  heat  the  second  cylinder  and  so  dry  the  sawdust, 
which  is  made  ready  for  distillation,  whilst  the  first  cylinder  is  discharged  and  again  charged 
with  fresh  sawdust.  In  Russia  and  America,  large  quantities  of  resinous  woods  are  distilled, 
and  these  yield  considerable  amounts  of  resins  and  oils  (of  pine,  turpentine,  etc. )  if  super- 
heated steam  is  used. 

A  large  works  was  started  at  Cassel  in  1900  to  distil  sawdust  according  to  the  Bergmann 
patents,  the  sawdust  being  strongly  compressed  into  bricks  with  the  hope  of  expressing 
the  moisture  and  obtaining  compact  charcoal ;  neither  of  these  ends  was  attained  and  the 
works  failed.  Similar  to  this  is  the  Heidenstam  process,  according  to  which  the  charcoal 
is  pressed  also  during  its  formation  or  distillation.  Biihler  (1902)  dries  the  sawdust  with 
the  hot  flue  gases  and  then  carbonises  it,  the  powdered  charcoal  being  pressed  with  tar 
and  fresh  sawdust  into  blocks,  which  are  afterwards  heated  in  a  charcoal  furnace  to  char 
the  sawdust  and  tar,  and  to  obtain  bricks  of  light  wood  charcoal;  the  volatile  products 
of  this  second  distillation  are  also  recovered.1 

In  1905  the  suggestion  was  made  to  distil  wood  in  retorts  in  a  current  of  chlorine  so  as 
to  obtain  acetic  and  hydrochloric  (70  per  cent,  of  the  chlorine  used)  acids  at  the  same  time, 
but  grave  difficulties  were  encountered  in  obtaining  a  material  resistant  to  these  acids. 
Further,  Larsen  constructed  rotary  furnaces  for  the  distillation  of  wood,  and  in  1904  an 
attempt  was  again  made  in  Sweden  to  distil  resinous  woods  with  superheated  steam  so 
as  to  obtain  an  increased  yield  of  turpentine. 

The  liquid  products  from  the  dry  distillation  of  wood  are  condensed  in  cooling  coils  and 
collected  in  large  wooden  vats.  They  consist  mostly  of  an  aqueous  solution  of  acetic  acid 
(see  Table  in  preceding  note),  methyl  alcohol  (about  1  per  cent.),  and  acetone  (nearly  O'l 
per  cent. ),  and  of  small  quantities  of  other  acids  (formic,  propionic,  butyric,  valeric,  caproic, 
etc. ).  On  this  liquid  floats  part  of  the  tar,  the  rest  of  which  collects  at  the  bottom ;  the 
tar  may  be  easily  separated  by  decantation  or  by  means  of  a  centrifuge — such  as  is  used 
for  the  separation  of  cream  from  milk — a  low  temperature  and  sometimes  addition  of  a 
little  tannin  being  used  to  facilitate  the  separation.2  The  aqueous  solution,  which  is 
brown,  and  has  an  unpleasant  odour  owing  to  the  presence  of  empyreumatic  products, 
may  be  treated  in  various  ways  according  as  crude  acid  or  a  purer  acid  is  required.  In 
the  first  case  it  is  filtered  through  wood- char  coal,  left  to  stand  for  a  week  to  see  if  any 
further  tar  separates,  and  then  distilled  fractionally  from  a  large  copper  still ;  the  methyl 
alcohol  and  acetone  are  first  collected  (at  60°  to  70°)  and  then  the  crude  pyroligneous  acid 
(beyond  95°),  which  has  a  strong  empyreumatic  odour,  turns  brown  rapidly  in  the  air  and 
contains  6  to  8  per  cent,  of  acetic  acid. 

None  of  the  attempts  made  to  purify  and  deodorise  this  product  have  given  satisfactory 
results  and  to  obtain  a  less  impure  acetic  acid,  calcium  acetate  is  first  formed  and  from  this 
the  acetic  acid  recovered  (see  later). 

The  separation  of  the  various  components  of  the  crude  pyroligneous  acid  and  the 
simultaneous  preparation  of  calcium  acetate  is  usually  effected  by  a  process  in  which  three 
boilers  are  employed  (Fig.  241).  The  crude,  decanted  pyroligneous  acid  is  pumped  into 
the  large  vat,  A,  from  which  it  passes  to  the  copper  boiler,  B^  (3000  to  5000  litres),  where 
it  is  boiled  by  means  of  steam-pipes  (steam  entering  at  V  under  3  to  4  atmos.  pressure 
and  the  condensed  steam  issuing  at  S).  The  vapours  of  acetic  acid,  methyl  alcohol  and 
acetone  are  passed  through  the  tube,  t,  to  the  bottom  of  the  second  boiler,  B2  (1000  to 

1  Sawdust  from  the  wood  of  the  Coniferse  (resinous )  is  not  suitable  for  distillation,  as  it  gives 
lower  yields  of  charcoal,  acetic  acid  and  methyl  alcohol  than  that  of  deciduous  trees,  especially 
of  hard  woods ;  further  such  sawdust  contains  scarcely  any  of  the  valuable  pine  oil  and  the  tar 
is  of  little  value. 

2  The  tar  is  washed  with  water  and  heated  to  recover  the  acetic  acid  it  contains,  the  tar  thus 
obtained  free  from  acid  being  used  in  the  manufacture  of  rubber  and  of  electric  cables,  its  price 
being  4s.  to  5s,  per  cwt. 


336 


ORGANIC    CHEMISTRY 


2000  litres),  filled  with  milk  of  lime  (from  the  lime-tank,  L),  which  soon  becomes  heated 
nearly  to  boiling  but  retains  the  greater  part  of  the  acetic  acid  as  calcium  acetate,  whilst 
the  vapours  proceed  through  the  boiler,  J33,  which  also  contains  milk  of  lime ;  finally, 
the  methyl  alcohol  and  acetone  vapours  are  condensed  in  the  cooler,  jB4,  and  collected 
in  the  reservoir,  D,  after  passing  through  the  test-glass,  m,  which  indicates  the  density 
(see  Fig.  131,  E,  p.  160,  and  Fig.  134,  E,  p.  161 ).  The  distillation  goes  on  until  the  density 
reaches  the  value  1-00,  this  usually  occurring  when  one-third  or  one-quarter  of  the  total 


FIG.  241. 

liquid  of  the  boiler,  Bv  is  distilled.  The  first  methyl  alcoholic  liquid  which  condenses, 
being  more  concentrated  (30  to  40  per  cent. ),  is  kept  and  rectified  apart  from  the  remaining 
more  dilute  liquid  by  means  of  an  ordinary  rectifying  column,  Hv  H2,  H3,  in  Fig.  241 
(see  also  Fig.  140,  p.  165). 

The  aqueous  tarry  residue  left  in  Bv  after  evaporation  of  all  the  acetic  acid,  is  discharged 
into  the  movable  tank,  M. 

When  the  liquid  in  the  second  boiler,  B2,  assumes  an  acid  reaction,  the  vapour  from 
Bt  is  passed  into  B3,  whilst  J32  is  discharged  into  the  vat,  Fv  below,  and  again  filled  with 
milk  of  lime,  into  which  the  vapours  from  B3  pass  before  they 
proceed  to  the  condenser,  54;  a  similar  change  is  then  made 
when  the  contents  of  B3  become  acid,  and  so  on.  The  calcium 
acetate  (about  20  per  cent.)  is  pumped  to  the  filter-press,  E, 
and  the  clarified  solution  collected  in  the  vat,  C,  which  feeds 
the  evaporating  pans  (iron  or  copper)  fitted  at  the  bottom  with 
a  lens-shaped  jacket,  Cr  This  is  best  seen  in  Fig.  242 :  the 
steam  for  heating  is  passed  in  at  a  and  the  condensed  steam 
runs  off  at  6;  /  is  a  hood  fitted  with  counter-weights,  g,  and 
hence  capable  of  being  raised,  its  object  being  to  carry  off  the 
irritating  acid  vapours  rising  from  the  pan.  More  effective  are 
pans  with  double  concave  bottoms.  The  concentration  readily 
attains  a  value  of  40  per  cent. ;  the  liquid  then  becomes  pasty 


FIG.  242. 


and  must  be  stirred,  this  being  continued  until  the  mass  will  crumble  between  the 
fingers.  The  acetate  is  then  lightly  roasted  at  125°  to  145°  on  iron  or  copper  plates  heated 
by  the  hot  gases  from  the  pans  or  from  the  furnaces  used  for  distilling  the  wood.  By  this 
means  the  mass  loses  the  residual  water  and  certain  volatile  tarry  and  empyreumatic 
products  retained  by  the  mass,  which  changes  from  brown  to  grey,  if  it  is  kept  well  mixed 
until  it  can  be  powdered  between  the  fingers.  For  this  roasting  use  is  also  made  of  con- 
tinuous furnaces  similar  to  the  Hasenclever  apparatus  for  making  calcium  hypochlorite 
(see  Vol.  I.,  p.  624),  steam  at  about  200°  being  passed  in  at  the  bottom  of  the  apparatus 
instead  of  chlorine.  In  this  way  a  product  containing  up  to  80  to  82  per  cent,  of  calcium 
acetate  is  obtained.  According  to  U.S.  Pat.  927,135  (1909)  white  calcium  acetate  of  very 


CALCIUM    ACETATE 


337 


high  purity  (86  to  92  per  cent.  )  is  obtained  if  the  concentration  and  drying  are  carried  out 
in  a  vacuum.  The  product  is  then  broken  up  somewhat,  and  sold  in  bags  holding  60  to 
70  kilos.  It  contains  80  to  84  per  cent,  of  pure  calcium  acetate,1  10  to  12  per  cent,  of  water 
(half  of  which  is  lost  only  at  about  -150°),  and  6  to  7  per  cent,  of  impurities  (CaCO3,  CaO, 
tarry  matters,  etc.). 

F.  H.  Meyer  (Ger.  Pat.  214,558,  1908)  obtains  calcium  acetate  free  from  phenolic 
compounds  (which  calcium  acetate  usually  holds  very  tenaciously  in  the  form  of  an  emul- 
sion) by  passing  the  gases  from  the  distillation  of  the  wood  —  when  freed  from  tar  —  into 
a  tower  containing  lumps  of  calcium  carbonate,  which  combines  with  the  acetic  acid  but 
not  with  the  phenols. 

Also  the  fractional  condensation  method  described  in  U.S.  Pat.  969,635,  1910  (I.  Heckel), 
although  somewhat  complicated,  represents  a  marked  improvement. 

To  obtain  acetic  acid  from  calcium  acetate,  the  latter  was  formerly  decomposed  with 
hydrochloric  acid.  Nowadays,  however,  the  decomposition  is  effected  with  concentrated 
sulphuric  acid,  the  substances  being  mixed  slowly  in  shallow  iron  pans  arranged  over  a 
furnace  and  fitted  with  covers  and  stirrers  :  for  100  kilos  of  calcium  acetate,  65  to  70  kilos 
of  commercial  sulphuric  acid  of  66°  Be.  In  order  to  avoid  the  formation  of  sulphur  dioxide 
and  other  decomposition  products  at  the  high  temperature  attained  initially  and  pre- 
vailing during  the  distillation,  K.  Linde  distils  in  a  vacuum  with  steam-heat  (superheated 
if  necessary);  this  procedure  renders 
the  operation  more  rapid  and  the 
acetic  acid  purer,  besides  reducing 
the  consumption  of  sulphuric  acid 
almost  to  the  theoretical  amount 
(60  kilos)  and  allowing  of  the  treat- 
ment of  larger  quantities  of  material 
at  a  time  ;  further,  the  final  portions 
of  acetic  acid,  which  are  retained 
with  great  tenacity  by  the  calcium 
sulphate,  may  be  more  easily  and 
completely  separated.  The  left-hand 
half  of  Fig.  243  shows  diagram- 
matically  the  arrangement  used  in 
treating  calcium  acetate,  when 
vacuum  distillation  is  not  employed. 
The  sacks  of  calcium  acetate,  a,  on 

the  upper  floor  are  tipped  through  a  hopper  on  to  the  flat  cast-iron  pans,  b,  fitted  with 
stirrers  ;  the  pans  are  then  closed  and  the  measured  amount  of  sulphuric  acid  in  n 
(supplied  from  the  large  leaden  tanks,  e),  slowly  introduced.  The  mass,  which  begins 
to  heat,  is  then  heated  by  the  fire  underneath,  the  stirrers  being  kept  in  motion 
meanwhile. 

The  acetic  acid  is  gradually  evolved  from  the  copper  tube  leading  first  to  the  vessel,  c, 
where  the  powder  and  acid  spray  carried  over  are  deposited,  and  then  to  the  copper  coils 
in  d,  where  the  acetic  acid  is  condensed  and  cooled,  to  be  collected  in  the  tank,  m  ;  a  lateral 
test-glass,  containing  an  aerometer,  is  fitted  to  the  condenser  and  allows  the  density  of 
the  distilled  acid  to  be  read  off  at  any  moment.  When  the  vapour-delivery  tube  begins 
to  cool,  the  operation  is  at  an  end;  the  fire  is  then  covered  with  ashes  and  the  residual 
calcium  sulphate  discharged  through  a  wide  lateral  tube,  Tf,  and  conveyed  from  the  factory 
by  an  archimedean  screw.  Another  distillation  is  then  immediately  commenced. 

1  The  strength  of  commercial  calcium  acetate  is  determined  by  introducing  a  homogeneous 
sample  of  5  grams  into  a  distilling  flask  with  50  c.c.  of  water  and  50  c.c.  of  pure  phosphoric  acid 
(sp.  gr.  1-2)  ;  the  mixture  is  shaken  and  heated  gently  to  avoid  frothing,  the  distillation  products 
being  cooled  and  condensed.  When  the  residue  becomes  dense,  the  distillation  is  continued  in  a 
current  of  steam.  The  distillation  is  continued  until  the  distillate  amounts  to  about  200  c.c.  ; 
this  is  then  made  up  to  250  c.c.  Part  of  this  liquid  is  tested  for  hydrochloric  and  phosphoric 
acids  and  50  c.c.  of  it  is  titrated  with  normal  caustic  soda  solution  with  phenolphthalein  as 
indicator  to  determine  the  amount  of  acetic  acid  ;  1  c.c.  of  the  normal  soda  solution  corresponds 
with  0-079  gram  of  calcium  acetate.  This  titration  also  gives,  besides  acetic  acid,  traces  of 
other  volatile  acids  contaminating  the  calcium  acetate,  but  this  error  is  inevitable.  Aqueous 
solutions  of  pure  calcium  acetate  have  the  following  densities  :  5  per  cent.,  1-0330  ;  10  per  cent., 
1-0492;  15  per  cent.,  1  -0660;  20  per  cent.,  1-0874;  25  per  cent.,  1-1130;  30  per  cent.,  1-1426. 
VOL.  II.  22 


-  243. 


338  ORGANIC    CHEMISTRY 

The  yield  from  100  kilos  of  calcium  acetate  amounts,  under  favourable  conditions,  to 
80  kilos  of  72  to  75  per  cent,  acetic  acid,  which  always  contains  a  few  per  cent,  of  sulphurous 
acid.  Part  of  the  latter  has  been  already  eliminated  during  the  distillation  as  uncondensed 
gas  and  carried  to  the  chimney.  During  recent  years  the  introduction  of  vacuum  dis- 
tillation has  been  almost  universal,  as  it  economises  fuel,  gives  an  increased  yield  and  a 
purer  product,  and  accelerates  complete  distillation  with  a  minimal  production  of  sulphurous 
acid. 

It  will  be  readily  understood  that  the  use  of  less  concentrated  sulphuric  acid  and  moist 
calcium  acetate  gives  a  more  dilute  acetic  acid.  A  large  part  of  the  acetic  acid  is  put  on 
the  market  as  it  is  or  diluted  with  water  to  bring  it  to  a  concentration  of  40  per  cent.,  which 
is  often  required  practically. 

When,  however,  purer  and  more  concentrated  acid  is  desired,  use  is  made  of  a  rectifying 
column  quite  similar  to  those  employed  in  the  case  of  alcohol  (see  p.  165).  The  column 
is,  however,  constructed  of  copper,  as  this  metal  is  more  resistant  (although  not  com- 
pletely so)  than  others  towards  organic  acids,  if  air  is  excluded.  The  heating  is  carried 
out  with  indirect  steam  under  5  atmos.  pressure,  which  circulates  in  coils  at  the  bottom  of 
the  still.  The  copper  column  is  fitted  inside  with  perforated  plates  of  porcelain  or  baked 
clay  arranged  alternately  with  copper  or  clay  rings;  the  condenser  consists  of  a  copper, 
or,  more  rarely,  a  clay  coil.  The  right-hand  half  of  Fig.  243  represents  the  rectifying 
apparatus  :  g  is  the  still,  h  the  column,  /  the  dephlegmator,  and  i  the  condenser.  When 
the  apparatus  is  not  in  use  it  is  well  rinsed  and  then  completely  filled  with  water,  in  order 

to  prevent  the  acid,  in  presence  of  air,  from 
attacking  the  copper.  The  first  portion  (about 
one-fourth)  of  the  distillate  is  kept  separate,  as 
it  is  more  dilute  and  contains  the  sulphurous 
anhydride  and  a  large  part  of.  the  empyreumatic 
products,  and  the  last  tenth  or  more  is  not 
distilled,  but  is  also  kept  separate,  being  very 
impure.  According  as  more  or  less  foreshots 
and  tailings  are  separated,  a  very  concentrated 
(96  to  99  per  cent.)  acid,  or  one  of  about 
80  per  cent,  strength  is  obtained,  both,  how- 
ever, containing  traces  of  copper  and  empy- 
reumatic products;  the  latter  may  be  removed  by  mixing  the  acid  in  clay  vessels 
with  a  little  concentrated  potassium  permanganate  and  then  filtering.  The  empyreumatic 
substances  may  also  be  removed  (e.  g.,  in  the  manufacture  of  essence  of  vinegar)  by  dis- 
tilling the  acid  over  potassium  chromate.  Traces  of  copper  are  eliminated  by  redistilling 
this  acid  from  a  copper  still  by  means  of  indirect  steam,  the  condensing  coils  and  tubes 
being  of  earthenware  or  silver  and  carboys  being  used  for  collecting  the  pure,  refined  acid. 
Nowadays  it  is  sometimes  considered  preferable  to  construct  the  small  head  of  the  still 
and  the  whole  of  the  refrigerating  coil  of  silver,  as  is  shown  in  Fig.  244,  since  the  coil  then 
conducts  heat  well  and  is  not  much  more  expensive  than  the  two  earthenware  coils  necessary 
to  give  the  same  rapidity  of  condensation;  besides  which,  earthenware  coils  are  fragile 
and  of  no  value  when  broken.1  According  to  Ger.  Pat.  220,705,  1907,  pure  acetic  acid 
containing  only  traces  of  SO2  may  be  obtained  by  heating  calcium  acetate  (100  parts)  to 
130°  in  a  vacuum  and  then  introducing  a  mixture  (55  parts)  of  equal  amounts  of  acetic  and 
concentrated  sulphuric  acids;  by  continuing  the  heating  in  a  vacuum,  the  whole  of  the 
acetic  acid,  including  that  added,  distils  over,  the  yield  being  95  per  cent. 

During  the  winter  care  must  be  taken  not  to  cool  the  condensing  coils  too  much,  as 
otherwise  the  pure  (glacial)  acetic  acid  may  solidify  and  cause  obstruction.  Also  in  stores 
where  acetic  acid  is  kept  in  wooden  casks,  earthenware  vessels,  or  carboys,  the  temperature 

1  Testing  of  acetic  acid.  If  no  empyreumatic  products  are  present,  a  mixture  of  10  c.c.  of 
the  acid,  15  c.c.  of  water,  and  1  c.c.  of  0-1  per  cent,  potassium  permanganate  solution  will  remain 
reddish  in  colour  for  more  than  one  minute.  The  acid  should  not  contain  higher  homologous 
acids ;  these  are  detected  by  dissolving  PbO  (litharge )  in  the  30  per  cent,  acid  until  only  a  faint 
acidity  remains,  the  solution  being  then  heated  and  filtered ;  if  the  crystals  which  form  are  not 
transparent  and  colourless,  but  show  white  flocks  like  mould,  the  acid  is  to  be  rejected.  The 
presence  of  other  organic  acids  in  acetic  acid  may  also  be  detected  by  fractionally  precipitating 
the  silver  salt  and  determining  the  silver  in  the  separate  fractions  by  heating  in  a  crucible.  Pure 
silver  acetate  contains  64-6  per  cent,  of  silver.  For  other  tests  see  note  on  p.  340. 


USESOFACETICACID  339 

must  be  maintained  above  16°  if  troublesome  solidification  of  large  quantities  of  the  acid 
is  to  be  avoided.  Glacial  acetic  acid  is  also  prepared  by  distilling  92  parts  of  pure  dehydrated 
(by  fusion  at  240°)  sodium  acetate  with  98  parts  of  concentrated  sulphuric  acid.  In  1901, 
the  Rhenania  chemical  firm  patented  a  process  for  distilling  calcium  acetate  with  a  sodium 
polysulphate,  NaH3(S04)2,  which  acts  like  sulphuric  acid  but  without  giving  secondary 
decomposition  products.  Formerly,  glacial  acetic  acid  was  obtained  by  Melsen's  reaction 
(1844),  which  consists  in  adding  potassium  acetate  to  dilute  acetic  acid  and  evaporating 
until  a  salt,  combined  with  acetic  acid,  crystallises ;  this  salt,  which  melts  at  148°,  decom- 
poses at  200°  to  250°,  pure  glacial  acetic  acid  distilling  and  the  potassium  acetate  (which 
decomposes  only  above  300°)  remaining  for  a  subsequent  operation. 

SYNTHETIC  ACETIC  ACID  FROM  CALCIUM  CARBIDE.  This  process  was 
described  on  p.  171 ,  in  the  chapter  on  synthetic  alcohol.  In  a  works  erected  by  the  Societa 
Italiana  Prodotti  Sintetici  (SIPS)  to  make  use  of  the  Lonza  process,  the  oxidation  of  the 
acetaldehyde  formed  as  an  intermediate  product  (see  p.  171 )  is  to  be  effected  by  means  of 
oxygen  from  liquid  air.  The  economical  synthetic  manufacture  of  acetic  anhydride  seems 
assured,  and  glacial  acetic  acid  will  probably  be  obtained  with  the  help  of  the  dilute  acetic 
acid  produced  by  the  older  processes. 

USES  OF  ACETIC  ACID.  Considerable  quantities  of  commercial  acetic 
acid  (35  to  40  per  cent. )  are  used  in  printing  and  dyeing  wool  and  silk,  especially 
with  "alizarin  and  other  dyes  which  withstand  feebly  acid  baths ;  it  is  also 
largely  employed  for  giving  silk  its  characteristic  rustling  property  after  dyeing 
or  cleaning.  The  pure  acid  serves  in  the  preparation  of  numerous  acetates 
(ammonium,  chromium,  and  aluminium — which  are  used  in  dyeing  fabrics 
and  rendering  them  impervious — lead,  etc.),  different  esters  and  various 
aniline  dyes.  After  it  became  obtainable  in  a  pure  state  by  rectification,  it 
acquired  great  importance  for  the  preparation  of  essence  of  vinegar  (various 
aromatic  herbs  being  added)  and,  when  diluted  with  water,  replaces  ordinary 
table  vinegar. 

Glacial  acetic  acid  serves  also  to  separate  the  paraffin  wax  from  Lignite  and 
petroleum  tars  (see  pp.  94  and  97).  According  to  Tanne  and  Oberlander 
(Ger.  Pats.  226,136  and  227,334, 1909),  100  kilos  of  petroleum  residues  is  treated 
in  the  hot  with  45  kilos  of  benzine  and  5  kilos  of  glacial  acetic  acid,  the  liquid 
being  decanted  off  and  cooled  slowly  for  twelve  hours ;  the  dishes  containing 
the  solution  are  then  kept  in  a  refrigerating  chamber  below  0°,  the  paraffin 
wax  separating  being  finally  removed  by  means  of  hydraulic  presses. 

It  has  been  proposed  to  denature  acetic  acid,  to  be  used  in  chemical 
industries,  by  addition  of  formic  acid,  so  that  it  may  be  freed  from  taxation  (in 
Italy). 

STATISTICS  OF  ACETIC  ACID  AND  CALCIUM  ACETATE.  Before  the  European 
war  but  little  calcium  acetate*was  produced  in  Italy,  but  large  quantities  of  calcium  acetate 
were  imported  from  the  United  States  (import  duty  8s.  per  ton)  and  treated;  this 
importation  amounted  to : 

1903     1905     1910     1913     1914     1915      1916      1917      1918 

Tons          .     407       1,625       1,320      2,326      2,023      2,604        2,168        2,891          847 
Value,  £    .      —      12,654     13,199    27,314    21,040    63,300     130,080    208,200    61,000 

Large  amounts  of  acetic  acid  of  various  strengths  are  also  imported  into  Italy.1 

1  The  manufacture  of  crude  pyroligneous  acid  in  Italy  is  exempt  from  taxation,  but  the 
rectification  and  production  of  the  pure  acid  are  subject  to  a  manufacturing  tax  of  12s.  per 
quintal  (of  pure  acid )  for  acid  of  less  than  10  per  cent,  strength ;  41s.  for  10  to  30  per  cent,  acid ; 
72s.  for  30  to  50  per  cent,  acid ;  100s.  for  50  to  70  per  cent,  acid ;  129s.  for" 70  to  90  per  cent,  acid; 
and  144s.  for  stronger  acid.  The  Customs  import  tariff  adds  a  further  tax  of  from  19d.  to  17s.  Qd. 
according  to  the  strength.  The  production  of  pure  dilute  acetic  acid  for  artificial  vinegar  is 
usually  effected  by  the  oxidation  of  alcohol,  which  is  supplied  almost  free  from  the  alcohol  tax, 
although  the  acetic  acid  tax  remains. 


340  ORGANIC    CHEMISTRY 

For  Germany  the  importation  and  exportation  are  as  follows  (tons) : 

1905       1908      1910     1911       1912      1913 

Calcium  acetate  imported  .      .        20,500     17,394     17,860     20,408     21,690     20,920 
Glacial  acetic  acid  or  anhyd-\        _  ^2QQ       1?57()       l>m       ^u       ^^ 

ride  exported  J 

The  calcium  acetate  is  imported  principally  from  the  United  States  and  partly  also  from 
Austria.  In  Germany  itself  more  than  16,000  tons  of  the  acetate  are  made  annually.  In 
1910  Germany  imported  4800  tons  of  dilute  pyroligneous  acid  (less  than  30  per  cent, 
strength)  for  purification. 

The  output  of  calcium  acetate  in  the  United  States  x  was  400,000  tons  in  1900  and  about 
800,000  tons  in  1914,  one-half  being  exported  (360,000  tons  in  1911).  The  acetic  acid 
consumed  in  the  United  States  amounted  to  14,000  tons  in  1900  and  13,500  tons  in  1905, 
14  per  cent,  being  used  in  making  dyes,  3  per  cent,  for  lead  acetate,  25  per  cent,  in  paper- 
making,  45  per  cent,  in  the  textile  industries  (dyeing),  14  per  cent,  for  making  white  lead, 
and  9  per  cent,  for  other  purposes. 

In  1910  the  wood  from  200,000  hectares  (490,000  acres)  of  forest  was  distilled  in  France, 
various  products  of  the  value  £600,000  being  obtained.  The  amounts  of  calcium  acetate 
imported  and  exported  were  as  follows  (ions) : 

1913  1914  1915  1916 

Importation        .         .     180  969  498  790 

Exportation        .         .     315  41  729  60 

Great  Britain  imported  3500  tons  of  calcium  acetate  in  1909  and  4300  tons  (£86,400) 
in  1910. 

In  1909  Brazil  imported  acetic  acid  to  the  value  of  £120,000. 

TLc  price  of  the  acid  varies  with  the  purity  and  concentration;  ordinary  commercial 
30  per  cent.  (sp.  gr.  1-041)  was  sold  before  the  war  at  about  12s. ;  the  40  per  cent,  acid 
(sp.  gr.  1-052)  at  15s.  to  16s. ;  and  the  50  per  cent,  acid  (sp.  gr.  1-061)  at  20s.  per  cwt.  The 
pure  acid  costs  25  per  cent,  more  than  the  commercial  at  the  same  concentration,  and  the 
pure  glacial  (99  to  100  per  cent.)  44s.  to  46s.  per  cwt.2 

MANUFACTURE  OF  VINEGAR 

Vinegar  is  formed  by  the  acetic  fermentation  (by  means  of  Mycoderma  aceti,  Bacillus 
aceticus,  or  Bacterium  aceti,  see  p.  145,  Fig.  116,  a)  of  saccharine  liquids  which  have  under- 
gone alcoholic  fermentation,  such  as  wine,  beer,  cider,  etc.  Since  this  transformation  of 
alcohol  into  acetic  acid  takes  place  merely  on  exposure  of  these  liquids  to  the  air,  it  is 

1  In  the  United  States  the  distillation  of  wood  has  been  organised,  both  technically  and 
commercially,  as  a  large  modern  industry,  all  the  works  being  combined  to  a  syndicate,  which 
regulates  the  trade  in  calcium  acetate  with  the  whole  world.     In  1900  1,767,380  cu.  metres  of 
wood  were  distilled  and  in  1907  about  4,391,000  cu.  metres  (only  10  per  cent,  of  resinous  wood) 
in  100  distilleries,  the  mean  yield  being  0-5  cu.  metre  of  charcoal,  8  to  10  litres  of  82  per  cent, 
methyl  alcohol,  22  to  25  kilos  of  80  to  82  per  cent,  calcium  acetate,  and  15  to  20  litres  of  tar  per 
cu.  metre  of  wood,  and  with  a  consumption  of  0-6  cu.  metre  of  wood  for  heating  the  retorts,  stills 
and  other  plant.     One-half  of  the  output  of  the  United  States  is  supplied  by  Michigan  and  one- 
fourth  by  Pennsylvania. 

In  Canada  there  are  wood-distilling  works  at  Quebec,  Ontario  and  Montreal,  where  also 
products  from  other  factories  are  treated.  Altogether  2300  workpeople  are  employed,  the 
annual  output  being  80,000  tons  of  wood  charcoal,  of  the  value  £120,000,  14,000  tons  of  calcium 
acetate,  of  the  value  £100,000, 400  tons  of  acetone,  worth  £240,000,  and  1400  casks  of  formaldehyde, 
worth  £100,000. 

2  Testing  of  Acetic  Acid.     Better  than  by  the  specific  gravity  the  strength  is  determined  by 
titrating  a  weighed  quantity  of  the  acid  with  normal  caustic  soda  solution  (1  c.c.  =  0-06004 
gram  of  acetic  acid)  in  presence  of  phenolphthalein.     When  the  acid  contains  more  than  2  per 
cent,  of  water  it  no  longer  dissolves  cedarwood  oil  or  oil  of  turpentine.     Metallic  impurities  are 
detected  by  diluting  10  c.c.  to  100  c.c.,  neutralising  with  ammonia  and  adding  ammonium  sul- 
phide and  then  ammonium  oxalate  :   the  pure  acid  should  show  no  alteration  or  precipitate. 
If  sulphuric  acid  is  absent,  the  acid,  diluted  with  10  volumes  of  water  and  treated  in  the  hot  with 
barium  chloride,  gives  no  precipitate  even  on  standing  for  some  hours.     In  absence  of  hydro- 
chloric acid,  dilution  and  addition  of  nitric  acid  and  silver  nitrate  produces  no  turbidity.     Absence 
of  empyreumatic  products  is  shown  by  mixing  5  c.c.  of  the  acid  with  15  c.c.  of  water  and  5  c.c. 
of  centinormal  permanganate  solution  :    the  liquid  should  not   become  decolorised  in  fifteen 
mimites.     For  the  detection  of  other  organic  acids  in  acetic  acid  and  other  tests,  see  notes  on 
pp.  338  and  344. 


VINEGAR 


341 


probable  that  vinegar  and  hence  acetic  acid  was  the  first  acid  known  to  man.  The  same 
result  is  obtained  by  treating  alcohol  with  various  oxidising  agents  (chromic  acid,  ozone, 
manganese  dioxide  and  sulphuric  acid,  etc.),  hut  acetaldehyde  is  also  largely  formed  in 
these  cases,  which  hence  do  not  compete  in  practice  with  the  biological  process.  The 
composition  of  vinegar 'was  studied  by  Berzelius  (1814),  and  Kiitzing  in  1837  showed 
the  importance  of  the  living  organism  of  the  mother-of- vinegar  to  the  formation  of  acetic 
acid,  while  Turpin  in  1840  examined  and  characterised  these  micro-organisms  more  exactly. 
According  to  Liebig,  the  transformation  of  alcohol  into  acetic  acid  is  brought  about  by 
the  catalytic  action  of  certain  nitrogenous  substances  capable  of  fixing  oxygen  from  the 
air  and  of  yielding  it  to  the  alcohol.  In  1868,  however,  Pasteur  showed  that  this  pheno- 
menon is  caused  by  a  vegetable  organism,  Mycoderma  aceti,  formed  of  small,  oblong  cells 
(about  3  micro-mm.  long),  slightly  constricted  in  the  middle  (where  segmentation  then 
takes  place)  and  often  arranged  in  chains.  When  these  multiply  at  the  surface  of  the 
alcoholic  liquid,  they  form  first  a  thin  membrane  which  gradually  thickens,  and  when  this 
membrane  is  formed  in  the  body  of  the  liquid  it  becomes  mucilaginous  and  spreads  through 
the  whole  liquid,  giving  a  compact  mass — the  so-called  mother-qf-vinegar — reaching  to 
the  surface.  It  develops  very  well  in  slightly  alcoholic  liquids  (3  to  6  per  cent.,  but  better 
with  13  per  cent,  of  alcohol,  and  still  more  readily  in  presence  of  about  1  per  cent,  of  acetic 
acid  and  0-1  per  cent,  of  phosphate);  the  most  favourable  temperature  is  about  30°,  aceti  - 
fication  ceasing  at  45°  or  below  5°;  the  action  is  retarded  by  light.  When  the  acetic 
membrane  becomes  submerged,  the  fermentation  ceases  and  only  recommences  with  the 
formation  of  a  fresh  superficial  membrane,  which  can  absorb  oxygen  from  the  air  and 
transfer  it  to  the  alcohol :  1 

CH3  •  CH2  •  OH  +  02  =  H20  +  CH3  •  COOH. 

According  to  this  equation,  the  theoretical  yield  is  60  grams  of  acetic  acid  per  46  grams 
of  alcohol,  but  the  practical  yield  is  15  to  20  per  cent,  less  than  this;  under  the  most 
favourable  conditions,  a  liquid  containing  10  per  cent,  of  alcohol  by  volume  yields  a  vinegar 
with  10  per  cent,  of  the  acid  by  weight.  When  almost  all  of  the  alcohol  is  converted  into 
acetic  acid,  part  of  the  latter  begins  to  decompose  into  H20  -4-  C02 ;  this  change  may  be 
avoided  by  continuing  to  add  alcohol  to  the  acetic  liquid  or  by  causing  the  mother-of- 
vinegar  to  sink,  and  decanting  the  liquid.  The  old  or  slow  wine  vinegar  process,  known 
as  the  Orleans  process,2  has  been  replaced  almost  everywhere  by  the  more  rapid  German 

1  This  explains  the  harmful  effect  of  vinegar  worms  (small  worms  belonging  to  the  Nematodes ), 
which  form  a  transparent,  white,  slimy  mass  moving  -along  the  walls  of  the  vessel,  and  breaking 
the  skin  of  Mycoderma  aceti  at  the  surface 

of  the  liquid  and  hence  causing  it  to  sink.  i_ 
Another  enemy  of  vinegar  is  the  vinegar  mite 
(an  insect  J  mm.  in  length ),  which  multiplies 
at  an  enormous  rate  and  accumulates  in 
large  masses  in  the  vinegar,  succeeding  in 
interrupting  the  acetic  fermentation  and 
starting  putrefactive  changes.  In  order  to 
prevent  the  entry  of  these  insects  into  the 
vats  and  casks,  the  latter  are  smeared  out- 
side with  a  ring  of  birdlime,  to  which  the 
mites  become  fixed.  Direct  sunlight  also 
hinders  the  development  of  the  worms. 
Also  Mycoderma  vini  hinders  the  develop- 
ment of  Mycoderma  aceti,  and  equally  harm- 
ful to  acetic  fermentation  are  antiseptic 
substances  in  general,  sulphur  dioxide  and 
empyreumatic  substances  (including  those  of  pyroligneous  acid).  Blue  and  violet  light  (hence 
white  light,  but  not  red  or  yellow  light)  likewise  retard  the  growth  of  Mycoderma  aceti. 

2  This  process  is  one  of  the  oldest,  and  was  formerly,  and  is  still,  carried  out  more  especially 
in  the  town  of  Orleans,  by  filling  a  number  of  superposed  casks  (Fig.  245)  to  the  extent  of  one- 
eighth  of  their  volume  with  good  wine  vinegar  and  then  adding  each  week  about  10  litres  of  wine 
(or  wine-dregs,  containing  8  to  10  per  cent,  of  alcohol,  filtered  through  beech  shavings  in  the  vat, 
E;   white  wines  are  preferable).     When  the  casks  are  about  half -full,  the  vinegar  is  made,  and 
two-thirds  of  it  is  drawn  off  and  either  filtered  through  beech  chips  or  allowed  to  deposit  in  the 
vat,  R',  underneath ;   the  addition  of  10  litres  of  wine  per  week  is  then  continued.     By  means 
of  the  stove,  X,  the  temperature  is  maintained  at  25°  to  30°.     This  method  gives  a  fine,  aromatic 
vinegar,  but  it  is  very  slow  and  cannot  be  interrupted  when  desired.     Pasteur  prepared  vinegar 
of  an  inferior  quality  more  rapidly  by  adding  a  little  vinegar  to  wine  in  wide,  shallow  vats  and 
then  sowing  on  the  surface  a  little  pure  Mycoderma  aceti  from  another  vat. 


FIG.  245. 


342 


ORGANIC    CHEMISTRY 


FIG.  246. 


after  one  or  two  complete  circula- 


process,  proposed  by  Schiitzenbach  in  1823  and  subsequently  greatly  improved.  As  early 
as  1730,  however,  Boer  have  prepared  vinegar — and  in  some  places  his  method  is  used  even 
to-day — by  means  of  two  vats  standing  on  feet  and  communicating  at  the  bottom  by 
means  of  a  tube.  One  vat  is  filled  with  the  wine,  but  the  other  is  only  about  half  filled, 
the  vinasse  not  being  submerged.  Every  twelve  hours  the  full  vat  is  half  emptied  into  the 

other.     If  the  temperature  is  kept  at  25°  to  30°,  acetification 
is  complete  in  12  to  15  days. 

In  the  German  or  quick  vinegar  process,  wooden  vats,  2-5 
to  3  metres  high  and  1-5  to  2  metres  in  diameter,  are  used 
(Fig.  246).  These  are  filled  almost  completely  with  beech 
shavings,  which  are  supported  on  a  perforated  false  bottom, 
L,  and  covered  with  a  wooden  disc  with  perforations 
traversed  by  cords  held  by  knots  so  as  to  form  a  uniform 
spray  of  the  alcoholic  liquid  (8  to  10  per  cent.),  mixed  with 
one-fifth  of  its  volume  of  wine  vinegar,  over  the  wood  chips. 
Six  or  seven  glass  tubes  passing  through  the  upper  disc 
allow  of  a  continuous  circulation  of  air,  which  enters  at 
the  periphery  of  the  lower  part  of  the  vat  through  the 
holes,  Z,  and  through  the  pipe,  R,  passes  through  the 
shavings — which  become  gradually  warmed  as  acetification 
proceeds — and  issues  through  the  apertures,  Zf,  at  the 

top.  The  temperature  is  shown  by  a  thermometer,  T,  inserted  in  a  glass  tube,  reaching 
to  the  middle  of  the  vat.  When  the  temperature  exceeds  40°,  it  is  lowered  by  a  more 
rapid  passage  of  the  alcoholic  liquid,  which  collects  at  E  and  is  discharged  by  the  siphon, 
H,  to  be  conveyed  to  the  top  of  the  vat  and  again  circulated  through  the  shavings,  this 
process  being  continued  until  acetification  is  complete.  In  some  cases  three  such  vats  are 
superposed,  the  liquid  passing  down  through  them  all ; 
tions  the  operation  is  complete,  although  the  amount 
of  acid  formed  is  not  equal  to  that  of  the  alcohol  in 
the  original  liquid. 

The  liquids  thus  obtained  contain  up  to  12  to  13 
per  cent,  of  acetic  acid  (14  per  cent,  cannot  be 
exceeded,  as  the  Mycoderma  would  then  be  killed) 
and,  if  the  operations  are  conducted  with  care,  less 
than  10  per  cent,  of  the  alcohol  used  is  lost ;  other- 
wise, especially  if  the  temperature  becomes  too  high, 
so  that  part  of  the  alcohol  evaporates,  the  loss  may 
amount  to  30  to  50  per  cent. 

Vinegar  of  an  inferior  quality  is  largely  prepared 
nowadays  from  various  alcoholic  liquids  made  from 
cereals,  starch,  beetroot,  or  molasses,  just  as  in- 
dustrial alcohol  is  prepared,  but  such  vinegar  lacks 
the  pleasant  aroma  of  wine  vinegar.  During  recent 
years,  however,  especially  in  Germany,  alcohol 
vinegar  has  been  greatly  improved  by  using  pure 
cultures  of  selected  bacteria.  In  1912,  about  30,000 
hectolitres  of  alcohol  were  converted  into  vinegar  in 
Austria  and  150,000  in  Germany. 

It  has  been  proposed  to  accelerate  acetification 
by  means  of  compressed  air,  but  greater  success 
has  attended  the  Michadis  or  Luxemburg  method,  in  which  acetification  is  carried  out 
in  rotating  casks  (5  to  6  hectolitres)  filled  with  beech  shavings  (washed  first  with  hot 
water  and  then  with  hot  vinegar)  and  traversed  by  two  osier  tubes,  one  along  the  horizontal 
axis  and  the  other  along  the  vertical  axis,  to  allow  of  the  circulation  of  air.  The  shavings 
are  washed  with  wine  vinegar,  and  the  cask  about  half  filled  with  wine  (Fig.  247). 
During  the  first  three  days  the  casks  are  rotated  three  times  a  day  and  subsequently  six 
times  a  day.  Acetification  is  complete  in  about  eight  days. 

An  ingenious,  rapid,  and  continuous  method  for  the  manufacture  of  vinegar  is  that 
of  Villon  (Fig.  248),  which  makes  use  of  two  drums  (2  metres  by  2  metres),  B  B,  arranged 


FIG.  247. 


MANUFACTURE    OF    VINEGAR 


343 


inside  in  the  form  of  a  spiral.  The  iron  spirals  are  covered  or  varnished  with  gutta-percha, 
and  are  30  metres  in  length,  the  coils  being  10  cm.  apart  and  the  spaces  between  filled  with 
beech  shavings  (washed  with  HCI )  or  charcoal.  The  drums  rotate  in  opposite  directions, 
the  left-hand  one  rotating  once  in  five  minutes  and  dipping  up  each  time  8  litres  of  the 
alcoholic  liquid  from  the  vessel,  C,  this  liquid  being  then  passed  through  the  axial  tube  to 


FIG.  248. 

the  second  drum,  which  discharges  it  into  the  other  dish,  C.  The  liquid  then  passes  to  a 
similar  pair  of  drums  and  thence  to  a  third  pair,  on  leaving  which  the  vinegar  is  ready ; 
by  this  means  1000  litres  are  produced  in  twenty  hours.  By  means  of  the  pump,  R,  a 
current  of  air  is  drawn  through  each  drum  to  the  centre,  whence  it  passes~through  the 
tube,  V,  to  a  cooling  coil,  S,  to  condense  the  small  amount  of 
acetic  acid  vapour  it  carries  over. 

Another  continuous  and  very  rapid  method,  which  avoids  loss 
of  acetic  acid  or  aldehyde  and  diminishes  the  labour  necessary 
by  establishing  more  intimate  contact  between  the  alcoholic 
liquid  and  the  subdividing  material,  is  that  in  which  the  stave 
acetifier  (Figs.  249  and  250)  is  used.  This  consists  of  a  wooden 
box,  P,  about  1  metre  wide  and  2  metres  high,  terminating  at 

the  top  in  a  channel,  R.  The  box 
is  filled  with  nine  or  ten  layers  of 
thin  beech  sticks,  placed  vertically 
and  very  close  one  to  the  other. 
The  position  of  the  sticks  in  one 
layer  is  crossed  with  respect  to  that 
of  the  sticks  in  the  next  layer. 
These  sticks  are  held  apart  by 
small  strips  of  wood  so  as  to  allow 
of  the  passage  of  a  thin  film  of 
liquid  downwards  and  of  the  air 
upwards.  The  total  surface  of  the 
sticks  in  an  apparatus  of  the 
dimensions  stated  above  amounts 
to  more  than  1000  sq.  metres,  so 
that  the  oxidation  is  extraordinarily 
rapid,  while  the  working,  which 
may  continue  uninterruptedly  for 
years,  is  extremely  regular  and 
simple.  The  air  enters  at  a  lateral 
slit,  Z,  at  the  bottom,  this  being 
covered  with  gauze  to  prevent 
access  of  harmful  insects,  and  the  draught  is  regulated  by  a  slider  in  the  exit-channel, 
JB;  the  vinegar  is  discharged  at  E.  The  thermometer,  T,  shows  the  temperature  of 
the  air  as  it  leaves.  The  figure  shows  also  the  contrivance  for  feeding  the  apparatus 
regularly  and  continuously  with  the  alcoholic  liquid.  The  latter  is  contained  in  the 
tank,  B,  in  which  is  a  wooden  float,  F ,  moving  along  three  vertical  rods,  L,  and 
carrying  the  glass  siphon,  W,  terminating  in  a  rubber  tube  with  a  regulating  clip,  n. 
The  liquid  from  the  siphon  falls  into  a  tube,  G,  and  thence  through  the  tube,  A  C,  to 
the  vessel,  H  (3  litres  capacity),  and,  when  this  is  full,  it  discharges  through  the 
siphon,  r,  on  to  the  perforated  plate,  V,  which  distributes  the  liquid  as  a  fine  spray  over 


FIG.  249. 


FIG.  250. 


344  ORGANIC    CHEMISTRY 

the  bundles  of  sticks,  and  is  traversed  by  several  glass  tubes  to  allow  of  the  escape  of  the 
ascending  air.  In  this  way  the  flow  of  liquid  from  B  is  independent  of  the  amount  of 
liquid  present  in  it  at  any  instant  (that  is,  of  the  pressure  it  exerts ).  The  clip,  n,  is  regulated 
so  that  the  vessel,  H,  is  refilled  and  discharges  its  3  litres  of  liquid  every  one  or  two  hours 
(or  in  any  other  prearranged  time). 

Attempts  have  been  made  to  replace  the  ordinary  biological  acetification  by  chemical 
oxidation  of  the  alcohol  by  means  of  platinum  black  or  even  of  ozone,  but  neither  method 
has  attained  to  practical  importance. 

Vinegar  is  kept  in  full  casks  in  stores  like  those  used  for  wine,  but  it  is  not  injured 
by  a  high  air-temperature.  An  excess  of  air  in  the  vessels  and  the  continued  presence 
of  the  mother-of- vinegar  lower  its  strength,  and,  when  this  becomes  too  low,  putrefaction 
may  develop.  Its  keeping  properties  and  aroma  may  be  enhanced  by  pasteurisation 
(see  pp.  186,  210)  at  50°  to  60°.  A  weak  vinegar  may  be  strengthened  and  kept  if  a  little 
pure  acetic  acid  is  added  to  it. 

WINE  VINEGAR  (white  or  red)  is  distinguished  from  other  vinegars  by  its  aroma, 
due  partly  to  ethyl  acetate  and  to  small  proportions  of  aldehydes.  It  usually  contains 
6  to  9  per  cent,  of  acetic  acid  and  less  than  1  per  cent,  of  alcohol,  and  has  the  density  1-015 
to  1-020.  The  extract  and  the  ash  have  the  same  compositions  as  those  of  wines,  the 
former  being  rich  in  cream  of  tartar. 

BEER  VINEGAR  contains  4-5  to  6  per  cent,  of  extract  rich  in  maltose,  dextrin, 
albuminoids,  and  phosphates,  and  exempt  from  cream  of  tartar. 

This  vinegar  also  contains  less  acetic  acid  and,  since  it  does  not  keep  so  well  as  that 
from  wine,  is  used  to  break  down  excessively  strong  vinegars. 

ARTIFICIAL  VINEGARS,  prepared  from  purely  alcoholic  liquids  or  from  acetic  acid 
and  a  colouring  material  such  as  caramel,  have  very  little  extract  and  no  cream  of  tartar, 
whilst  the  percentage  of  acetic  acid  sometimes  reaches  12  or  13. 

In  the  ANALYSIS  OF  VINEGAR,  the  density  of  the  extract  and  the  ash  are  deter- 
mined as  with  wine  (p.  186).  The  content  of  acetic  acid  cannot  be  estimated  exactly 
with  standard  alkali  solution,  since  other  acids  (tartaric,  succinic,  etc. )  present  influence  the 
titration;  nor  do  the  graduated  tubes  (acetometers)  give  accurate  results.  A  more  exact 
determination  is  effected  by  distilling  the  acetic  acid  in  a  current  of  steam,  as  in  the  analysis 
of  calcium  acetate  (p.  337). 

Adulteration  of  vinegar,  which  is  somewhat  frequent,  is  detected  by  the  following  tests: 
Real  wine  vinegar  exhibits  certain  relations  between  the  acetic  acid  and  extract.  In  wine 
the  ratio  is  4  parts  of  alcohol  for  about  1  of  extract,  after  deduction  of  the  sugar  present 
in  sweet  wines;  assuming  a  loss  of  15  per  cent,  of  the  alcohol  during  the  conversion  into 
vinegar,  a  pure  wine  vinegar  with  5-31  per  cent,  of  acetic  acid  should  contain  1-08  per 
cent,  of  extract;  one  with  7-15  per  cent,  of  acid,  1-44  per  cent,  of  extract;  one  with  8-9 
per  cent,  of  acid,  1-8  per  cent,  of  extract,  and  one  with  10-7  per  cent,  of  acid,  2-16  per  cent, 
of  extract,  the  ratio  of  acid  to  extract  always  being  about  4-9 :  1.  Addition  of  malt  or 
beer  vinegar  is  recognised  by  its  reduction  of  Fehling's  solution,  or  by  concentrating  80  c.c. 
of  the  vinegar  to  about  2  c.c.  and  then  adding  alcohol :  the  formation  of  a  white  precipitate 
-(dextrin)  soluble  in  much  water  indicates  such  adulteration  with  certainty. 

If  mineral  acids  have  been  added,  4  or  5  drops  of  a  dilute  alcoholic  solution  of  methyl 
violet  (1  :  10,000)  will  give  a  greenish  colour  with  25  c.c.  of  the  vinegar;  also,  with  zinc 
sulphide,  hydrogen  sulphide  is  evolved ;  finally,  after  the  vinegar  has  been  heated  with 
a  trace  of  starch,  it  will  not  give  a  blue  colour  with  iodine.  The  presence  of  sulphuric 
acid  in  vinegar  is  detected  by  the  white  precipitate  formed  with  barium  chloride,  hydro- 
chloric acid  by  that  given  by  silver  nitrate,  and  oxalic  acid  by  the  formation  of  a  white 
precipitate  with  calcium  chloride. 

Artificial  colouring-matters  are  detected  in  the  same  way  as  in  wine  and  beer,  and 
pyroligneous  acid  by  the  furfural  reaction  (see  this). 

The  price  of  good  wine  vinegar  is  little  less  than  that  of  wine,  but  artificial  vinegars  are 
cheaper. 

France  produces  annually  600,000  to  700,000  hectolitres  of  vinegar,  but  in  Italy  the  pro- 
duction is  much  less,  owing  to  the  competition  of  artificial  vinegar  and  to  the  excessive 
duty  of  17s.  6d.  per  hectolitre;  in  1904-1905  the  thirty-eight  Italian  vinegar  factories  con- 
sumed 6160  hectolitres  of  alcohol,  the  output  of  artificial  vinegar  being  60,000  hectolitres.  In 
1912  55,000  hectolitres  of  artificial  vinegar  were  made.  In  Germany  70  per  cent,  of  the 


ACETATES  345 

vinegar  is  made  from  alcohol,  the  consumption  of  the  latter  being  41,110  hectolitres  in 
1911-1912  and  23,000  hectolitres  in  1912-1913. 

DERIVATIVES   OF  ACETIC  ACID 

SALTS  OF  ACETIC  ACID.  These  are  termed  acetates,  and  are  all  soluble 
in  water  (the  least  soluble  are  silver  and  mercurous  acetates).  They  are  readily 
formed  by  neutralising  acetic  acid  with  metallic  oxides  or  carbonates,  previously 
dissolved  in  water.  Pure  anhydrous  acetic  acid  or  its  alcoholic  solution  does  not 
decompose  alkaline  carbonates,  so  that  C02  precipitates  potassium  carbonate 
from  an  alcoholic  solution  of  potassium  acetate,  acetic  acid  being  liberated. 

Even  in  aqueous  solution,  acetic  acid  undergoes  only  slight  dissociation,  but 
the  acetates  are  considerably  dissociated  and  diminish  the  dissociation  and 
hence  the  acid  characters  of  acetic  acid  (see  Vol.  I.,  p.  100). 

POTASSIUM  ACETATE  (Normal),  CH3  •  COOK,  melts  at  229°  and  is  soluble  in  water 
or  alcohol.  It  is  obtained  by  neutralising  potassium  hydrogen  carbonate  (KHCO3)  solution 
with  acetic  acid  and  evaporating  to  dryness.  The  acid  acetate,  CH3  •  COOK,  C2H402,  is 
obtained  by  dissolving  the  normal  acetate  in  acetic  acid  and  separates  from  the  latter  in 
crystals  which  melt  at  148°  and  decompose  at  200°,  liberating  anhydrous  acetic  acid. 

A  Diacid  Potassium  Acetate,  CH3  •  COOK,  2C2H4O2,  melting  at  112°,  is  also  known. 

The  commercial  refined  normal  acetate  costs  about  £3  per  cwt. 

SODIUM  ACETATE,  CH3  •  COONa,  crystallises  from  water  with  3H2O,  melts  at 
100°,  loses  water  and  solidifies  at  a  higher  temperature  and  then  melts  only  at  319°. 

In  the  cold  it  dissolves  to  some  extent  (1 :  23)  in  alcohol  or  in  its  own  weight  of  water, 
giving  a  feebly  alkaline  solution  and  considerable  lowering  of  temperature. 

It  is  prepared  by  neutralising  pyroligneous  acid  almost  completely  with  sodium  carbonate 
and  concentrating  the  solution  (after  removal  of  the  tar  from  the  surface)  to  27°  Be. ;  the 
crystals  which  separate  on  cooling  are  centrifuged,  but  are  always  reddish  brown.  The 
mother-liquors  (which  readily  become  mouldy)  are  taken  to  dryness  and  lightly  roasted 
to  burn  the  tarry  products.  Crude  sodium  acetate  is  preferably  prepared  by  treating 
calcium  acetate  solution  with  sodium  sulphate  and  then  with  a  little  soda  to  precipitate 
all  the  lime ;  the  filtered  or  decanted  solution  is  evaporated  to  dryness,  heated  to  250°, 
redissolved  in  water,  concentrated,  and  allowed  to  crystallise. 

According  to  C.  Bauer,  pure  sodium  acetate,  free  from  the  reddish-brown  colour,  may 
be  prepared  directly  from  pyroligneous  acid  by  neutralising  with  sodium  carbonate,  and 
adding  to  the  solution  concentrated  to  27°  Be.,  2  per  cent,  of  caustic  soda,  the  liquid  being 
then  allowed  to  crystallise  in  wide  and  shallow  wooden  vessels.  The  crystals  are  separated 
by  centrifugation  and  redissolved,  the  small  amount  of  free  caustic  soda  being  then  neutral- 
ised with  commercially  pure  acetic  acid;  the  solution  is  boiled  to  expel  the  excess  of  acetic 
acid,  concentrated  to  27°  B6.,  and  left  to  crystallise. 

Acid  sodium  acetates  are  also  known. 

Sodium  acetate  serves  for  the  preparation  of  pure  acetic  acid,  and  is  used  in  dyeing,  etc. 

Before  the  war,  crude  red  sodium  acetate  was  sold,  according  to  its  degree  of  purity, 
at  145.  to  18s.  per  cwt. ;  the  white  purified  crystals  (pharmaceutical)  at  24s.  to  28s. ;  and 
the  doubly  refined  and  fused  anhydrous  product  at  52s. 

AMMONIUM  ACETATE,  CH3  •  COONH4,  is  obtained  by  neutralising  hot  glacial 
acetic  acid  with  a  current  of  dry  ammonia  or  with  ammonium  carbonate.  The  pure 
crystals  which  separate  melt  at  113°  to  114°  and,  although  not  highly  hygroscopic,  dis- 
solve readily  in  water,  giving  an  alkaline  solution;  the  solution  in  acetic  acid  deposits 
the  acid  acetate  melting  at  66°.  The  salt  acts  as  a  sudorific  and  dissolves  lead  oxalate 
and  sulphate.  It  is  used  to  some  extent  in  dyeing. 

The  commercial  brown  solution  at  10°  Be.  costs  £1  per  cwt.  and  the  pure  solution  of 
the  same  density  25s. ;  chemically  pure  crystals  cost  £5  per  cwt. 

CALCIUM  ACETATE,  (CH3  •  COO)2Ca  +  2H2O.  The  preparation  of  the  commercial 
product  has  already  been  described  on  p.  336.  The  pure  salt  is  obtained  by  repeated 
crystallisation  from  water,  and  costs  up  to  48s.  per  cwt.  Its  solubility  in  water  diminishes 
with  rise  of  temperature  up  to  a  certain  point  and  subsequently  increases.  For  Statistics, 
see  p.  339. 


346  ORGANIC    CHEMISTRY 

FERROUS  ACETATE  (Pyrolignite  of  Iron),  (CH3  •  COO)2Fe.  The  crude  product, 
used  as  a  mordant  in  the  dyeing  and  printing  of  textiles,  is  obtained  from  pyroligneous 
acid  and  iron  filings,  or  from  calcium  pyrolignite  and  a  concentrated  solution  of  ferrous 
acetate ;  the  tarry  substances  present  preserve  it  from  oxidation.  A  solution  of  20°  Be. 
costs  6s.  per  cwt.  and  one  of  30°  Be.  8s.  6d.  The  pure  product  is  prepared  by  dissolving 
freshly  prepared  ferrous  hydroxide  in  30  per  cent,  acetic  acid. 

FERRIC  ACETATE,  (C2H3O2)3Fe,  used  as  a  mordant  in  dyeing,  is  obtained  from 
the  ferrous  salt  and  sodium  acetate.  It  gives  a  reddish-brown  solution  in  the  cold,  but 
in  the  hot  and  in  presence  of  a  large  amount  of  water,  a  reddish- brown  mass  of  basic  ferric 
acetate,  Fe(C2H302)2OH,  separates;  it  is  this  which  fixes  the  colouring- matters. 

ALUMINIUM  ACETATE  (Normal),  Al(C2H3O2)3,is  obtained  from  aluminium  sulphate 
and  the  corresponding  quantity  of  lead  acetate.  It  is  known  only  in  solution,  in  which 
it  gradually  undergoes  spontaneous  decomposition  into  acetic  acid  and  the  basic  acetate  : 
A1(C2H302)3  +  HaO  =  A1(C2H3O2)2OH  +  C2H4O2. 

When  the  solution  of  the  basic  acetate  is  boiled,  aluminium  hydroxide  and  acetic  acid 
separate  :  A1(C2H3O2)2OH  +  2H20  =  A1(OH)3  +  2C2H402. 

It  is  used  in  dyeing,  in  the  printing  of  textiles  and  in  the  preparation  of  waterproof 
fabrics.  For  the  last  purpose,  the  material  is  first  soaked  in  aluminium  acetate  solution 
and  then  heated  or  steamed,  A1(OH)3  thus  being  deposited  in  the  pores  of  the  fabric,  which 
is  rendered  impervious  to  water. 

BASIC  ALUMINIUM  ACETATE,  A1(C2H3O2)2OH  +  1JH2O,  is  obtained  crystalline 
by  evaporating  a  solution  of  the  normal  acetate  cautiously  at  a  temperature  not  exceeding 
38°;  it  is  soluble  in  water.  Dilute  solutions  (4  to  5  per  cent.)  of  the  normal  acetate 
gradually  deposit,  on  the  walls  of  the  containing  vessel,  a  porcelain-like  crust  of  a  basic 
acetate  with  2H20  or  2£H2O  :  this  is  insoluble  in  water. 

It  is  used,  like  the  normal  salt,  in  dyeing,  textile-printing,  etc. 

SILVER  ACETATE,  C2H3O2  •  Ag,  is  obtained  crystalline  by  adding  silver  nitrate 
to  a  concentrated  solution  of  an  acetate  (e.  g.,  that  of  ammonium).  It  is  a  characteristic 
salt,  crystallising  from  water  in  shining  needles  (solubility  1 :  100  at  20°,  2-5  :  100  at  80°). 
When  calcined  in  a  porcelain  crucible,  it  leaves,  like  all  organic  silver  salts,  pure  metallic 
silver. 

NORMAL  LEAD  ACETATE  (Sugar  of  Lead),  (CH3COO)2Pb  +  3H20,  forms 
monoclinic  plates  or  crystals,  has  a  disagreeable,  sweetish  taste,  is  poisonous, 
and  exhibits  a  faintly  acid  reaction.  It  is  slightly  soluble  in  alcohol  and  more 
so  in  water  (1  part  dissolves  in  1*5  parts  of  water  at  15°,  in  1  part  at  40°,  or 
in  0'5  part  at  100°).  It  loses  the  water  of  crystallisation  over  sulphuric  acid 
or  at  100°,and  then  melts  above  200°. 

It  is  used  as  a  mordant  in  the  dyeing  and  printing  of  textiles  and  also  in 
the  preparation  of  various  lead  salts  and  paints  and  certain  pharmaceutical 
products;  further,  for  conferring  hot-drying  properties  on  linseed  oil  to  be 
used  for  varnishes. 

Italy  produced  45  tons  in  1904,  80  in  1906,  140  in  1908,  200  (£5280)  in  1911,  39  in  1914, 
and  200  (£12200)  in  1915.  Germany  exported  1765  tons  in  1905,  2078  (£52,000)  in  1906, 
1677  in  1909,  1288  in  1910,  2080  in  1911,  1664  in  1912,  and  1626  in  1913. 

The  refined  crystalline  product  was  sold  before  the  war  at  24s.  to  28s.  per  cwt.,  and 
the  chemically  pure  at  36s. 

It  is  best  prepared  commercially  by  the  Bauschlicher-Bauer  method  (1892-1905) 
from  commercial  pure  60  per  cent,  acetic  acid  (see  Tests  on  pp.  338  -and  340)  and  pure 
litharge  containing  99  per  cent,  of  PbO.1  A  pitch-pine  vat  is  fitted  with  a  tight  cover 
with  three  apertures :  the  central  one  for  the  shaft  of  a  wooden  stirrer,  another  for  a 
copper  cooling  coil  to  condense  the  acetic  acid  vapours,  and  the  third  for  the  neck  of  a 
large  wooden  hopper,  by  means  of  which  the  litharge  is  dropped  on  to  a  wooden  distribut- 
ing roller  provided  with  teeth  and  placed  under  the  lid.  The  required  quantity  of  acetic 
acid  is  heated  to  60°  by  a  copper  steam  coil  in  the  bottom  of  the  vat,  and  the  litharge 

1  It  should  contain  neither  iron,  which  would  colour  the  crystals,  nor  aluminium,  which 
would  render  filtration  difficult. 


ACETATES  347 

gradually  added  in  the  proportion  of  103  kilos  per  100  kilos  of  60  per  cent,  acetic  acid ; 
each  100  kilos  added  requires  about  an  hour  to  dissolve  if  the  stirrer  is  kept  in  motion  and 
the  temperature  does  not  exceed  65°.  The  solution  has  a  density  of  70°  to  72°  Be.  and, 
if  it  does  not  show  an  acid  reaction,  it  is  slightly  acidified  with  acetic  acid,1  and  the  mother- 
liquor  (35°  to  37°  Be. )  from  a  preceding  operation  added  in  such  amount  that  the  density 
becomes  50°  to  52°  Be.  The  solution  at  65°  is  then  allowed  to  clarify  in  a  couple  of  tightly 
closed  wooden  vats,  each  fitted  with  a  horizontal  rail  carrying  strips  of  lead  dipping  into 
the  liquid  so  as  to  remove  the  small  amount  of  copper  present.  After  five  to  six  hours  the 
solution  is  passed  through  a  cloth  filter-press  with  wooden  channels,  and  is  then  left  to 
crystallise  in  wooden  vessels  for  eight  to  ten  days — until  the  density  of  the  mother-liquor  falls 
to  35°  Be.  in  winter  or  37°  in  summer.  If  the  solution  is  kept  at  60°,  as  crystals  separate 
the  vessel  may  be  fed  with  fresh,  more  concentrated  solution  until  a  thick  layer  of  crystals 
is  obtained ;  it  is  then  allowed  to  cool  for  some  days.  After  the  liquid  has  been  decanted, 
the  mass  of.  small  crystals  (more  concentrated  and  hotter  solutions  give  larger  crystals) 
is  treated  in  a  copper  centrifuge  and  dried  in  wooden  boxes  placed  in  a  vacuum  apparatus 
at  a  temperature  not  exceeding  30°. 2 

MONOBASIC  LEAD  ACETATE  (Subacetate  of  Lead),  (C2H3O2)2Pb  +  PbO  +  H2O, 
and  Dibasic  Lead  Acetate,  (C2H3O2)2Pb  +  2PbO,  are  obtained  by  melting  the  normal 
acetate  with  a  greater  or  less  proportion  of  litharge  (3  :  1  for  the  monobasic  salt)  on  the. 
water-bath;  the  former  is  readily  soluble  and  the  latter  only  slightly  so  (1  :  18  at  20° 
and  1  :  5-5  at  100°)  in  water.  The  lead  acetate  of  the  pharmacopoeia  is  a  2  per  cent,  solution 
of  the  monobasic  salt,  and  is  used  as  a  medicine ;  this  salt  is  used  also  for  weighting  silk, 
for  decolorising  vegetable  juices,  and  for  preparing  white  lead  and  aluminium  acetate. 
The  anhydrous  salt  former'y  cost  52s.  per  cwt. 

NORMAL  CHROMIC  ACETATE,  Cr(C2H3O2)3  +  H2O,  is  obtained  from  calcium  or 
lead  acetate  and  chrome  alum  or  chromic  sulphate.  It  gives  a  violet  solution,  which 
becomes  green,  without  decomposing,  when  heated. 

Basic  Chromium  Sulphate  is  obtained  in  a  similar  way  from  basic  chromium  sulphate 
or  by  adding  ammonia  or  sodium  hydroxide  or  carbonate  to  a  solution  of  the  normal 
acetate.  The  basicity  increases  with  the  amount  of  alkali,  the  compound,  Cr2(C2H302)5OH, 
being  gradually  converted  into  Cr2(C2H3O2)2(OH)4  or  even  more  basic  salts  still.  The 
more  basic  the  acetate  the  more  will  it  decompose  on  boiling  and  the  more  readily  it  will 
serve  as  a  mordant  in  dyeing  or,  better,  in  printing,  since  the  reducing  action  of  the  textile 
fibres  or  of  the  colouring-matters  or  of  other  organic  substances  added,  results  in  the 
separation  of  the  true  mordant,  Cr(OH)3,  which  forms  stable  lakes  with  the  dyes  (alizarin, 
hsematein  from  log- wood,  etc. ). 

Commercial  chromium  acetate  solutions  at  20°  Be.  were  sold  before  the  war  at  16s. 
per  cwt.,  those  of  40°  Be.  at  28s.,  and  the  solid  at  60s. ;  the  chemically  pure  acetate  cost 
8s.  per  kilo. 

STANNOUS  ACETATE,  Sn(C2H3O2)2,  is  obtained  by  treating  stannous  chloride 
with  lead  acetate  or  by  dissolving  freshly  precipitated  stannous  hydroxide  in  dilute  acetic 
acid.  Its  solution  is  used  as  a  mordant  or  corrosive  in  printing  cotton  with  substantive 
dyes  (see  this,  Part  III). 

The  20°  to  22°  Be.  solution  formerly  cost  24s.  per  cwt. 

NORMAL  CUPRIC  ACETATE  (Crystallised  Verdigris),  Cu(C2H3O2)2  +  H2O,  is 
obtained  by  dissolving  the  basic  acetate  (true  verdigris)  in  acetic  acid  or,  better,  by  decom- 
posing copper  sulphate  solution  with  lead  acetate.  It  forms  clinorhombic,  dark  green 
prisms  and  is  readily  soluble  in  hot  water  (1 :  5)  or  in  alcohol.  It  is  used  in  medicine  and 
has  been  suggested  as  a  means  of  combating  the  Peronospora  which  attacks  the  vine. 
Before  the  war  it  cost  2s.  6d.  per  kilo. 

1  The  subsequent  crystallisation  is  rendered  difficult  if  the  solution  contains  basic  acetate, 
the  presence  of  this  being  inferred  from  the  turbidity  produced  on  mixing  a  little  of  the  liquid 
with  an  equal  volume  of  1  per  cent,  corrosive  sublimate  solution. 

2  Analysis  of  lead  acetate  is  effected  by  dissolving  5  grams  of  it  in  water,  precipitating  the 
lead  with  a  known  quantity,  in  slight  excess,  of  normal  sulphuric  acid,  making  up  to  250  c.c., 
and  then  adding  a  volume  of  water  about  equal  to  that  of  the  precipitate.     In  50  c.c.  of  the 
nitrate,  the  sulphuric  acid  is  precipitated  with  barium  chloride,  the  weight  of  the  resulting 
barium  sulphate  giving  the  quantity  of  sulphuric  acid  which  has  remained  in  combination  with 
the  lead.     Another  50  c.c.  of  the  filtrate  is  titrated  with  normal  caustic  potash,  the  total  acidity 
thus  found  being  due  to  acetic  acid  and  excess  of  sulphuric  acid ;  deduction  of  the  latter  then 
gives  the  amount  of  acetic  acid  existing  in  combination  in  the  lead  acetate' 


348  ORGANIC    CHEMISTRY 

BASIC  COPPER  ACETATE  (Verdigris),  [2Cu(C2H3O2)OH]  +  5H2O,  is  obtained 
by  arranging  sheets  of  copper  with  flannel  saturated  with  hot  vinegar,  acetic  acid,  or  acid 
vinasse,  in  between.  The  crust  of  acetate  is  detached  from  the  plates  and  sold  in  cakes 
either  dry  or  with  30  to  40  per  cent,  of  moisture.  It  forms  blue  needles  or  scales,  which 
effloresce  in  the  air  and  become  green,  owing  to  loss  of  water. 

It  dissolves  only  slightly  in  water  and,  when  heated  in  the  dry  state,  gives  off  acetic 
acid  and  water.  When  pure,  it  is  completely  soluble  in  excess  of  ammonium  carbonate 
solution. 

Jt  was  formerly  used  as  a  colouring-matter,  but  is  now  used  for  the  preparation  of 
SchweinfurtK1  s  green  (copper  aceto-arsenite),  Cu(C2H302)2,  3CuAs204,  by  mixing  with  the 
requisite  proportion  of  arsenious  anhydride  solution ;  this  gives  a  beautiful  green  colouring- 
matter,  which  is  still  used  to  some  extent,  although  it  is  very  poisonous  owing  to  the 
evolution  of  hydrogen  arsenide  in  the  air. 

In  cakes  or  balls,  the  basic  acetate  formerly  cost  £3  per  cwt.,  whilst  the  refined  powder 
cost  £4  to  £5. 

PROPIONIC  ACID,  C3H602  or  CH3  •  CH2  •  COOH 

This  acid  is  obtained  by  hydrolysing  ethyl  cyanide  (see  p.  238),  or  by  oxidising  propyl 
alcohol  with  chromic  acid,  or  by  the  action  of  certain  micro-organisms  on  calcium  lactate. 
It  is,  however,  usually  prepared  by  fermenting  wheat-bran,  or  is  extracted  from  crude 
pyroligneous  acid,  being  formed  in  small  quantity  (2  to  4  per  cent. )  in  the  dry  distillation 
of  wood.  For  some  years  it  has  been  manufactured  by  the  Effront  process  (see  p.  183) 
from  the  residues  of  beetroot  molasses  :  1000  kilos  of  molasses  yield  75  kilos  of  ammonium 
sulphate  and  95  to  120  of  fatty  acids  consisting  largely  of  propionic  acid  (see  also  section  on 
Sugar). 

It  occurs  in  perspiration,  in  the  fruit  of  GingJco  biloba,  and  in  colophony  tar. 

It  is  a  liquid  of  sp.  gr.  0-996  at  19°  and  resembles  acetic  acid  in  odour  and  in  physical 
and  chemical  properties.  It  is,  indeed,  not  possible  to  separate  these  two  acids  by  dis- 
tillation and  rectification,  but  this  may  be  done  by  means  of  the  lead  salts,  basic  lead  pro- 
pionate,  3Pb(C3H502)2,  4PbO,  being  very  slightly  soluble  in  hot  water,  although  soluble  in 
cold.  It  boils  at  141°  and  solidifies  at  -22°.  It  forms  crystalline  salts  soluble  in  water, 
and  its  esters  have  a  fruity  aroma.  Chemically  pure  propionic  acid  formerly  cost  32s.  per 
kilo,  and  the  commercial  acid  14s.  6d.,  but  nowadays  the  Effront  process  yields  a  much 
cheaper  commercial  acid,  which  in  practice  may  be  used  to  replace  formic  and  acetic  acids, 
these  being  more  difficult  to  purify. 

BUTYRIC   ACIDS,   C4H8O2 

Two  isomerides  are  known  of  different  structures,  their  constitutional 
formulae  being  deduced  from  their  methods  of  synthesis. 

(1)  NORMAL  BUTYRIC  ACID  (Butanoic  or  Propylcarboxylic  Acid  or  Buty- 
ric Acid  of  Fermentation),  CH3  •  CH2  •  CH2  •  COOH,  is  the  more  important  of  the 
two  isomerides  and  exists  in  butter  in  the  form  of  glyceric  ester  to  the  extent 
of  4  to  5  per  cent.  It  is  formed  also  in  sweat  and  occurs  in  solid  excreta  and 
in  decomposing  cheese,  as  well  as  among  the  products  of  fermentation  of 
glycerine. 

It  is  obtained  practically,  not  by  synthesis  (see  p.  320),  but  by  the  butyric 
fermentation  of  starch-paste  in  presence  of  a  little  tartaric  acid,  putrefied  meat 
or  cheese  being  added  after  a  few  days  (pure  cultures  of  special  bacteria  are  also 
used  at  the  present  time) ;  it  is  obtained  also  from  acid  skim  milk  by  treatment 
with  powdered  marble  and  converting  the  calcium  lactate  into  calcium  butyrate, 
then  into  the  sodium  salt,  and  finally,  by  means  of  H2SO4,  into  the  free  acid. 
It  is  also  obtained  from  molasses  residues  by  Eff rent's  process  (see  above). 

It  forms  an  oily  liquid,  sp.  gr.  0'958  at  14°,  boib'ng  at  162°  and  solidifying 
in  scales  at  19°.  It  dissolves  in  water,  alcohol,  or  ether,  burns  with  a  bluish 
flame,  and  gives  crystalline,  slightly  soluble  salts. 

Calcium  Butyrate,  (C4H702)2Ca  -f  H2O,  is  less  soluble  in  hot  than  in  cold 
water. 


HIGHERACIDS  349 

The  esters  have  pleasant,  fruity  odours,  and  are  used  to  produce  artificial 
rum.  Commercial  concentrated  butyric  acid  cost  before  the  war  4s.  per  kilo  ; 
the  50  per  cent,  acid,  2s.  Qd.  ;  and  the  chemically  pure  (100  per  cent.),  5s.  IQd. 
The  concentrated  esters  were  sold  at  2s.  Qd.  to  5s.  per  kilo. 

CH 
(2)  ISOBUTYRIC  ACID  (2-Methylpropanoic  or  Dimethylacetic  Acid), 


COOH,  resembles  the  preceding  acid,  but  is  less  soluble  in  water.  It  boils  at  154° 
and  solidifies  at  —  79°,  and  occurs  free  in  arnica  and  carob  roots  and  as  ester  in  chamo- 
mile  oil.  .  It  may  be  obtained  by  the  ordinary  synthetic  processes  and  is  less  resistant  than 
the  normal  acid  to  oxidising  agents.  The  pure  acid  formerly  cost  40s.  per  kilo  and  the 
commercial  acid  about  one-half  as  much. 

The  Calcium  Salt,  Ca(C4H7O2)2,  is  more  soluble  in  hot  water  than  in  cold. 

VALERIC   ACIDS,   C5H10O2 

The  four  isomerides  predicted  by  theory  are  known. 

(1)  NORMAL  VALERIC  ACID  (Pentanoic  or  Propylacetic  Acid),  CH3  .  [CH2]3  . 
COOH,  is  a  dense  liquid  (sp.  gr.  0-956  at  0°),  boiling  at  185°  and  solidifying  at  —  58-5°.     It 
is  obtained  synthetically  from  propylmalonic  acid  or  butyl  cyanide,  and  is  met  with  in 
pyroligneous  acid  ;  it  is  slightly  soluble  in  water.     The  pure  product  cost  before  the  war 
5d.  per  gram. 

(2)  ISOVALERIC  ACID,  £n3>CH  '  CH2  '  COOH>  is  found  free  or  in  the  form  of 

3 

esters  in  animals  (fat  of  the  dolphin,  sweat  of  the  feet,  etc.)  and  vegetables  (roots  of 
Valeriana  officinalis),  and  from  the  latter  may  be  extracted  by  boiling  with  solutions  of 
soda  or  by  distilling  with  water  containing  phosphoric  acid.  It  is  a  liquid  (sp.  gr.  0-947 
at  0°),  boiling  at  174°  and  solidifying  at  -51°;  it  has  a  disagreeable  odour  of  stale  cheese. 
It  is  often  obtained  by  oxidising  fusel  oil  with  dichromate  and  sulphuric  acid.  The  pure 
acid  costs  96s.  per  kilo. 

Its  esters  are  used  as  artificial  fruit  essences,  and  cost  from  10s.  to  16s.  per  kilo. 

(3)  ETHYLMETHYLACETIC  ACID  (Methyl-2-butanoic  or  Active  Valeric  Acid), 

CH 

_,    3  >CH  •  COOH,  is  optically  active,  as  it  contains  an  asymmetric  carbon  atom  (see 

SH5 

p.  19)  ;  it  occurs  naturally  with  iso  valeric  acid.  The  inactive  mixture  of  the  two  oppositely 
active  acids  may  be  resolved  into  its  active  components  by  means  of  the  brucine  salts. 
It  boils  at  174°. 

(4)  TRIMETHYLACETIC    ACID    (Dimethyl  -  2  -  propanoic     or     Pivalic     Acid), 
(CH3)3  :  C  •  COOH,  is  a  solid,  m.-pt.  35°,  b.-pt.  163°.     It  has  an  odour  resembling  that  of 
acetic  acid,  and  it  may  be  obtained  from  tertiary  butyl  cyanide. 

HIGHER  ACIDS 

Of  the  numerous  isomerides  theoretically  possible  and  of  the  many  actually 
known,  mention  will  be  made  only  of  some  of  the  more  important  which  occur 
naturally  and  are  usually  of  the  normal  structure  and  with  even  numbers  of 
carbon  atoms. 

NORMAL  CAPROIC  ACID,  C6H1202  or  CH3  •  [CH2]4  •  COOH,  is  a  liquid  boiling  at 
205°  and  solidifying  at  -1-5°.  It  is  volatile  in  steam,  has  an  unpleasant  odour  like  rancid 
butter,  and  is  found  free  in  Limburger  cheese  and  coco-nut  oil,  and  as  glyceride  in  goats' 
butter.  It  is  formed  on  oxidising  proteins  or  higher  fatty  acids  (unsaturated). 

HEPTOIC  ACID  (CEnantic  Acid),  C7H14O2  or  CH3  •  [CH2]5  •  COOH,  is  formed  on 
oxidation  of  castor  oil  or  cenanthaldehyde.  It  is  a  liquid  boiling  at  220°  and  solidifying 
at  —  20°.  It  differs  from  its  lower  homologues  by  exhibiting  a  slight  odour  of  fat. 

CAPRYLIC  ACID  (Octoic  Acid),  C8H]6O2  or  CH3  •  [CH^  •  COOH,  solidifies  at  16-5° 
and  boils  at  237-5°  ;  it  is  found  in  coco-nut  oil  and  as  glyceride  in  ordinary  butter  and  that 
of  goats. 

NONOIC  ACID  (Pelargonic  Acid),  C9H18O2  or  CH3  •  [CH2]7  •  COOH,  is  a  liquid  boiling 
at  254°.  It  is  formed  by  oxidising  oleic  acid  or  by  decomposing  the  ozonide  of  oleic  acid 
(Molinari  and  Soncini,  1905)  with  dilute  alkali.  In  nature  it  occurs  in  Pelargonium  roseum. 


350  ORGANIC    CHEMISTRY 


DECOIC  ACID  (Capric  Acid),  C^H^C^  or  CH3  •  [CH^  •  COOH,  is  a  solid,  melting 
at  31-4°  and  boiling  at  200°  under  100  mm.  pressure.  It  also  is  found  in  coco-nut  oil  and 
goats'  butter. 

UNDECOIC  ACID,  CnH22O2  or  CH3  •  [CH2]9  .  COOH.  Distillation  of  castor  oil  under 
reduced  pressure  yields  the  unsaturated  undecenoic  acid,  CUH2002,  which  gives  undecoic 
acid  on  reduction  with  hydrogen.  It  melts  at  28°  and  boils  at  212°  (100  mm.). 

LAURIC  ACID,  C12H24O2  or  CH3  •  [CH^,,  •  COOH,  is  a  solid,  melting  at  44°  and 
boiling  at  225°  (100  mm.);  it  occurs  in  the  form  of  glyceride  in  laurel  berries. 

MYRISTIC  ACID,  ^H^Gg  or  CH3  -,[CH2]12  .  COOH,  melts  at  54°  and  boils  at  248° 
(100  mm.).  It  is  found  as  glyceride  (myristin)  in  the  nutmeg  (Myristica  moschata)  and 
in  ox-gall,  and  abounds  in  the  seeds  of  Virola  Venezuelensis. 

PALMITIC  ACID  (Hexadecoic  Acid),  C16H32O2  or  CH3  •  [CH2]14  •  COOH, 
forms  a  moderately  transparent  white  mass,  which  readily  softens  and  melts 
at  62*6°.  It  is  insoluble  in  water  and  crystallises  from  alcohol  in  scales  or 
needles.  It  boils  unchanged  at  268°  under  100  mm.  pressure,  or,  with  partial 
decomposition,  at  339°  to  356°  under  the  ordinary  pressure. 

It  is  one  of  the  normal  components  of  animal  and  vegetable  fats,  in  which 
it  occurs  as  a  glyceride  (palmitin),  and  is  easily  obtained,  together  with  oleic 
acid,  from  palm  oil  by  hydrolysing  and  then  decomposing  the  soap  formed; 
the  palmitic  acid  is  then  isolated  by  fractional  crystallisation.  Japanese 
vegetable  wax  or  Carnaiiba  wax  consists  almost  exclusively  of  palmitin.  The 
industrial  treatment  of  fats  and  oils  for  the  extraction  of  the  corresponding 
fatty  acids  (palmitic,  stearic,  and  oleic)  will  be  described  in  the  section  dealing 
with  the  manufacture  of  soap  and  candles. 

Commercial  palmitic  acid  is  also  known  by  the  inaccurate  name  of  'palmitin 
and  is  likewise  manufactured  by  melting  oleic  acid  with  potassium  hydroxide 
(Varrentrapp's  reaction)  :  C18H34O2  +  2KOH  =  H2  +  CH3  •  C02K  -f-  C^H^OaK 
(potassium  palmitate,  which  gives  palmitic  acid  under  the  action  of  mineral 
acid). 

Its  alkali  salts  (soaps)  are  soluble  in  alcohol  or  water,  but  considerable 
dilution  of  the  aqueous  solutions  results  in  the  separation  of  an  acid  salt  and 
liberation  of  alkali.  Whilst  in  alcoholic  solution  these  soaps  show  virtually 
normal  molecular  weights,  the  aqueous  solutions  show  no  rise  in  the  boiling- 
point,  the  soaps  thus  behaving  as  colloids  in  these  solutions  (see  Vol.  I.,  p.  105). 
The  Bother  salts  (palmitates)  are  insoluble  in  water  and,  in  some  cases,  soluble 
in  alcohol  ;  mineral  acids  liberate  palmitic  acid  from  them. 

Before  the  war,  the  commercial  acid  cost  £2  per  cwt.,  the  refined  product 
£4,  and  the  doubly  refined  25s.  Qd.  per  kilo. 

MARGARIC  ACID,  C17H34O2  or  CH3  •  [CH2]15  •  COOH,  was  for  a  long  time 
thought  to  exist  in  fats,  but  it  has  been  shown  that  a  mixture  of  palmitic 
(C16)  and  stearic  (C18)  acids  was  being  dealt  with.  Synthetically  it  is  obtained 
by  hydrolysing  cetyl  cyanide,  C16H33  •  CN,  and  by  other  methods.  It  melts 
at  60°  and  distils  unchanged  at  277°  under  100  mm.  pressure. 

STEARIC  ACID,  C18H36O2  or  CH3  .  [CH2]16  .  COOH,  which  is  improperly 
known  commercially  as  stearine  (and  is  then  mixed  with  palmitic  acid),  and 
its  separation  from  oleic  acid,  will  be  described  when  dealing  with  candles. 

As  glyceride,  it  occurs  with  that  of  oleic  acid  as  one  of  the  principal  con- 
stituents of  fats  and  oils,  and  is  usually  prepared  industrially  from  beef 
suet. 

Synthetically  it  may  be  obtained  by  the  reducing  action  of  hydrogen  on 
oleic  acid  (see  this),  and  the  constitution  of  the  latter  being  known,  that  of 
stearic  acid  follows  directly.  Industrial  application  is  now  made  of  this 
process  (see  Oleic  acid). 

It  forms  a  somewhat  soft  white  mass,  melting  at  69'3°,  and  crystallises 
from  alcohol  in  shining  scales.  It  boils  unchanged  at  287°  under  100  mm. 


UNSATURATED    ACIDS 


351 


pressure  or  with  partial  decomposition  at  359°  to  383°  under  the  ordinary 
pressure. 

It  is  insoluble  in  water,  soluble  slightly  in  light  petroleum,  and  more  readily 
in  alcohol,  ether,  benzene,  or  carbon  disulphide. 

Its  salts  behave  like  those  of  palmitic  acid.  The  lead  salts  of  these  high 
fatty  acids  are  obtained  by  boiling  the  fats  or  oils  with  lead  oxide  and  water. 
This  lead  soap  is  used  for  the  preparation  of  lead  plaster,  which  is  used  in 
medicine  and  in  the  manufacture  of  varnish.  Stearic  acid  made  into  a  paste 
with  gypsum  forms  a  kind  of  artificial  ivory. 

Italy  imported,  especially  from  France,  England,  and  Belgium,  the  following 
amounts  of  stearic  acid  : 


1908 

Tons      .     1,250 
Value,  £       — 


1910 

1,445 

63,560 


1912 
621 


1913 

920 
32,020 


1914 
698 


1915 

423 


1916 

119 


1917         1918 
58  152 

—     19,773 


CEROTIC  or  CEROTINIC  ACID,  C27H54O2,  is  found  free  in  beeswax  (together  with 
Melissic  Acid,  C30H60O2),  as  ester  in  Chinese  wax  and  as  glyceride  in  the  fat  of  raw 
wool.  It  melts  at  78'5°  and  is  converted  by  oxidising  agents  into  various  acids  with 
lower  molecular  weights. 


II.  UNSATURATED  MONOBASIC  FATTY  ACIDS 
A.  OLEIC  or  ACRYLIC  SERIES,  CnH2n_2O2  (Olefine-carboxylic  Acids) 


Empirical 
formula 

Name  of  acid 

Constitutional  formula 

Melting- 
point 

Boiling- 
point 

°3H4°2 

Acrylic  acid         ...                             .         . 

OH,  :  CH  •  CO2H 

13° 

140° 

(Vinylacetic  acid  . 

CH,,  :  CH  •  OK  •  C02H 

—  39° 

163° 

04H602 

Solid  crotonic  acid 
Liquid  crotonic  acid 

CH,  •  CH  :  CH  •  CO2H  (cis) 
CH,  •  OH  :  CH  •  C02H  (tram) 

72° 
15-5° 

181° 
169° 

Metacrylic  acid    . 

CK  :  C(CH3)  •  CO.H 

16° 

161° 

(  Angelic  acid    . 

CH'—  C—  CO,H 

06H802 

(8  structural  isomerides  and  one  J 
stereoisomeride)                 j 
l.Tiglic  acid 

II 
OH3—  C—  H 
CH,C—  CO,H 

45° 

185° 

II 

65° 

198-5° 

H—  C—  CH3 

p6TT10r>2 
C,H^02 

(Not  all  stereoisomerides  known)  Pyroterebic  acid  . 
Do.                         y-Allylbutyric  acid 
Do.                         Teracrylic  acid 

(CHgV  :  0  :  OH  •  CH2  •  CO2H 
(CnV).:  0  :  COOS4,,)  •  CH2  •  COoH 

—  15° 

207° 
226° 
218° 

C,0H18O2 

Do.                        Citronellic  acid     . 

CH^  :  0(CH3)  •  [CHJs  •  OH(CH3)  •  CHj  •  CO2H 

— 

152° 

(18  mm.) 

OHO 

Do.                        Undecenoic  acid  . 

CH«  :  OH  '  [CHojo  •  CO2H 

24-5° 

213-5° 

11     20    2 

"2 

(100  mm.) 

Ol6H3<>02 

Do.                        Hypogaeic  acid 
fOleicacid    . 

CH,  •  [OH,]7  •  CH  :  CH  •  [CHJ5  •  CO2H 
OH,  •  [CH^  •  OH  :  CH  •  [CHjj  •  CO2H  (ri*) 

14° 

223° 

Ol8H3402 

Do. 
l.Elaidicacid 

CH3  •  [OH2]7  •  CH  :  CH  •  \GB£1  '  C02H  (trans') 

51° 

(10  mm.) 
225° 

(10  mm.) 

Ol8H3402 

T,                        /  Iso-oleic  acid 
1  Aaj3-oleic  acid       . 

CH,  •  [CHJa  •  OH  :  CH  •  [CHJg  •  CO2H  (  ?) 
OH3  •  [CHJ14-  CH  :  CH  •  CO2H 

44° 

58° 

— 

/  Erucic  acid 

CH3  •  [CH^lj  *  CH  :  CH  •  [CH^jjj  •  C02H 

34° 

254-5° 

(10  mm.) 

OHO 

Do.                    -vBrassidic  acid 

CH,  •  [OHJ,  •  CH  :  CH  •  [CHJ,,  •  C02H 

65° 

256° 

22    42    2 

I 

* 

(10  mm.) 

I  Isoerucic  acid 

CH3  •  [CHJg-  CH  :  OH  •  [CHjlj,,'  CO2H  (  ?) 

55° 

~ 

The  importance  of  these  acids  is  due  to  the  fact  that  certain  of  them  occur 
as  glycerides  in  many  fats  and  oils. 

GENERAL  PROCESSES  OF  FORMATION.  The  following  are  the  most 
important  of  these  : 

(1)  The  unsaturated  halogen  derivatives  of  unsaturated  alcohols  may  be 
transformed  into  cyanogen  derivatives,  which  give  the  corresponding  acids 
on  hydrolysis  (see  p.  238)  : 

CH9  :  CH  •  CH9  •  OH  ->  CH,  :  CH  •  CH9  •  Br-> 


CH2  :  CH  •  CH2  •  CN 


CH2  :  CH  •  CH2  •  COOH. 


352  ORGANIC    CHEMISTRY 

(2)  Oxidation  of  unsaturated  alcohols  and  aldehydes  with  mild  oxidising 
agents  (silver  oxide  or  the  oxygen  of  the  air)  which  do  not  attack  the  double 
linking  ;  allyl  alcohol  and  acrolei'n  give  acrylic  acid. 

(3)  Of  general  use  is  Perkin's  reaction,  applicable  especially  to  the  aromatic 
series,  but  of  service  also  for  the  fatty  series  :    when  an  aldehyde  is  heated 
with  the  sodium  salt  of  a  saturated  fatty  acid  in  presence  of  an  anhydride 
(e.  g.,  acetic  anhydride)  and  then  treated  with  water,  the  resulting  products 
are  the  saturated  acid  corresponding  with  the  aldehyde  used  and  an  unsaturated 
acid,  which  always  has  the  double  linking  between  the  a-  and  ^-carbon  atoms, 
the  a-carbon  atom  being  that  adjacent  to  the  carbonyl  group,  CO.      If  the 
chain  united  to  the  aldehyde  group  is  denoted  by  R,  the  intermediate  phases 
of  this  reaction  are  probably  as  follow  : 

(a)  R  •  CHO  +  CH3  •  CO  •  0  •  CO  •  CH3  give,  by  aldol  condensation, 
R  •  CH(OH)  •  CH2  •  CO  •  O  •  CO  •  CH3  ;  this  unstable  compound  immediately 
separates  water,  giving  R  •  CH  :  CH  •  CO  •  0  •  CO  •  CH3,  treatment  of  this 
product  with  water  yielding  the  unsaturated  acid  : 

(6)  R-  CH  :  CH  •  CO  •  0  •  CO-CH3+H20  =  CH3'COOH  +  R-CH:CH-COOH. 

It  is  evident  that,  if  only  one  hydrogen  atom  is  united  to  the  carbon  atom 
adjacent  to  the  carbonyl  group  of  the  original  anhydride,  the  first  phase  of 
the  reaction,  but  not  the  second,  will  be  possible,  so  that  only  a  saturated 
hydroxy-acid  will  be  obtained  : 

R  •  CHO  +  CH  •  CO  •  O  •  0  •  CH  +  H2O  = 


R  •  CH(OH)  •  C  •  COOH  +  (CH3)2  :  CH  •  COOH. 


The  presence  of  the  sodium  salt  of  the  fatty  acid  is  indispensable  to  all 
these  reactions,  but  its  function  has  not  yet  been  explained. 

(4)  Similar  to  Perkin's  synthesis  is  the  reaction  between  an  aldehyde  (or 
an  a-ketonic  acid,  R  •  CO  •  COOH,  which  possibly  loses  C02  and  thus  gives 
an  aldehyde)  and  malonic  acid  in  presence  of  glacial  acetic  acid,  a  mixture 
of  unsaturated  monobasic  acids  with  the  double  linking  in  the  a  /?-  or  /?  y- 
position  being  obtained  and  C02  split  off  : 


(a)  R  •  CH2  -  CHO  +  CH2<  =  R  •  CH2  •  CH(OH) 

Malonic  acid 

(b)  2R  •  CH2  •  CH(OH)  •  CH<^^  = 

2C02  +  2H20  +  R  •  CH2  •  CH  :  CH  •  COOH  +  R  •  CH  :  CH  •  CH2  •  COOH. 

a  j3-acid  £  y-acid 

It  should  be  noted  that  this  reaction  always  gives  also  a  condensation 
product  of  1  mol.  of  the  aldehyde  and  2  mols.  of  malonic  acid,  this  product 
then  losing  C02  and  yielding  a  saturated  dibasic  acid  : 

R  •  CH<CH(COOH)2  -  9CO   4-  R  •  CH<CH2  '  COOH 
L^CH(COOH)2  -  2LU2  1  ^CH2  •  COOH 

(5)  When  monohalogenated  saturated  fatty  acids  (especially  those  with 
the  halogen  in  the  /3-position)  are  heated  with  alcoholic  potash,  or  sometimes 
even  with  water  alone,  a  molecule  of  halogen  hydracid  is  eliminated  and  the 
unsaturated  acid  formed  (similar  to  the  reaction  giving  unsaturated  hydro- 
carbons, p.  108)  : 

CH2I  •  CH2  •  COOH  =  HI  +  CH2  :  CH  •  COOH. 

/S-Iodopropionic  acid  Acrylic  acid 


OLEFINE-CARBOXYLIC    ACIDS  353 

(6)  By  separating  a  molecule  of  water  from  monohydroxy-acids  by  means 
of  distillation  or  a  dehydrating  agent  (H2S04,  PC15,  P205)  or  sometimes  by 
merely  heating  with  caustic  soda  solution,  the  unsaturated  monobasic  fatty 
acids  are  formed  : 

CH3  •  CH(OH)  •  CH2  •  COOH  =  H20  +  CH3  •  CH  :  CH  •  COOH. 

/3-Hydroxybutyric  acid  Crotonic  acid 

GENERAL  PROPERTIES.  The  number  of  double  bonds  is  ascertained 
by  the  same  methods  as  are  applied  to  unsaturated  hydrocarbons  (see 
p.  107) — by  addition  of  either  halogen  or  ozone.  These  unsaturated  acids 
are  more  energetic  than  the  corresponding  saturated  acids  with  the  same 
numbers  of  carbon  atoms,  as  may  be  seen  from  their  ionisation  constants 
(Vol.  I.,  pp.  102  et  seq.).  They  are  more  easily  oxidisable  than  the  corresponding 
saturated  acids,  powerful  oxidising  agents  rupturing  the  carbon  atom  chain  at 
the  double  linking,  the  position  of  which  may  hence  be  established  by  a  study 
of  the  compositions  of  the  two  acids  formed. 

When  boiled  with  10  per  cent,  caustic  soda  solution,  unsaturated  acids 
with  a  double  linking  (A )  in  the  /ty-position  undergo  displacement  of  this 
linking  with  the  partial  formation  of  unsaturated  acids  with  a  double  bond 
in  the  apposition  (Fittig,  1891-1894);  this  is  formed  from  an  intermediate 
hydroxy-acid,  an  equilibrium  being  established  as  indicated  below  : 

R  •  CH  :  CH  •  CH2  •  COOH  +  H2O  ^t  R  •  CH2  •  CH(OH)  •  CH2  •  COOH  <£ 

(3  -y-acid  /3-Hydroxy-acid 

H20  -f  R  •  CH2  •  CH  :  CH  •  COOH. 

a  (3-acid 

In  general  this  reaction  preponderates  towards  the  formation  of  the  a/?-acid 
and  not  vice  versa,  the  carboxyl  group  apparently  exerting  an  attraction  on 
the  double  linking. 

When  an  unsaturated  acid  is  fused  with  caustic  soda  or  potash,  the  double 
linking  is  displaced,  giving  an  a/?-acid,  the  new  molecule  immediately  splitting 
at  the  double  bond,  the  resultant  products  being  acetic  acid  and  another 
saturated  acid.  This  displacement  of  the  double  linking  was  unknown  until 
a  few  years  ago,  so  that  oleic  acid,  for  example,  which  gives  palmitic  and 
acetic  acids  quantitatively  when  fused  with  potash,  was  regarded  as  an 
ap -unsaturated  acid.  It  has,  however,  been  shown  (see  later)  that  the  double 
bond  of  oleic  acid  is  in  the  middle  of  the  molecule,  the  action  of  the  potash 
causing  displacement  of  this  bond  before  the  molecule  is  resolved  : 

CH3  •  [CH2]7  •  CH  :  CH  •  [CH2]7  •  COOH  -*  CH3  •  [CH2]14  •  CH  :  CH  •  COOH 

Oleic  acid  a  /3-Oleic  acid 

CH3  •  [CH2]14  •  CH  :  CH  •  COOH  +  2KOH  -f  0  = 
CH3  •  [CH2]14  •  COOK  +  H20  +  CH3  •  COOK. 

Potassium  palmitate 

The  acids  of  the  oleic  or  acrylic  series,  and  unsaturated  compounds  in 
general,  exhibit  a  tendency  to  polymerise ;  the  mere  action  of  sodium  alkoxide 
on  the  crotonic  esters  produces,  in  addition  to  other  reactions,  the  following 
change : 

CH3  C02-CH3  CH3  C02-CH3 

II  II 

CH  CH  CH  CH2 

II                        II                                        II  I 

CH  CH  C—       CH 

II  II 

C02'CH3         CH3  C02-CH3          CH3 

Methyl  crotonate  Methyl  dicrotonate 

VOL.  ii.  23 


354  ORGANIC    CHEMISTRY 

Instances  of  stereoisomerism  among  unsaturated  compounds  have  already 
been  described  on  pp.  21  and  22,  and  it  is  only  necessary  to  state  here  that,  of 
the  two  stereoisomerides  corresponding  with  one  and  the  same  formula,  one 
is  less  stable  than  the  other,  into  which  it  is  easily  and  directly  transformed 
(the  inverse  change  only  takes  place  indirectly)  by  mere  heating  or  by  the 
action  of  concentrated  sulphuric  acid,  caustic  soda,  a  little  nitrous  acid,  or 
a  trace  of  bromine  in  the  presence  of  light. 


ACRYLIC   ACID    (Propenoic  Acid) 
C3H4O2  or  CH2  :  CH  •  COOH 

This  acid  was  prepared  for  the  first  time  (Redtenbacher,  1843)  by  oxidising  acrolein, 
CH2  :  CH  •  CHO,  with  silver  oxide.  It  is  now  more  readily  obtained  indirectly,  by  the 
action  of  gaseous  hydrogen  chloride,  which  gives  /3-chloropropaldehyde,  CH2C1  •  CH2  •  CHO, 
this  being  converted  by  nitric  acid  into  the  corresponding  /3-chloropropionic  acid, 
CH2C1  •  CH2  •  COOH  ;  when  the  last  compound  is  boiled  with  a  solution  of  alkali,  it  loses 
HC1,  yielding  acrylic  acid. 

Another  convenient  synthesis  is  the  following  :  allyl  alcohol  (a,  see  below)  with  bromine 
gives  dibromopropyl  alcohol  (b),  which,  on  oxidation,  yields  a/3-dibromopropionic  acid  (c), 
and  this,  by  the  action  of  either  zinc  in  presence  of  dilute  sulphuric  acid  (or  water)  or 
reduced  copper  (containing  iron)  loses  bromine  and  gives  acrylic  acid  (d)  : 

CH2  CH2Br  CH2Br  CH2 

II  I  I  II    ' 

CH  -»  CHBr        ->          CHBr         ->         CH 

I  I  I  I 

CH2-OH  CH2-OH  COOH  COOH 

abed 

Acrylic  acid  is  a  liquid  soluble  in  water  and  having  a  pungent  odour  almost  like  that 
of  acetic  acid  :  it  has  the  sp.  gr.  1-0621  at  16°,  boils  and  polymerises  at  about  140°,  and 
when  cooled  forms  tabular  crystals  melting  at  13°.  With  nascent  hydrogen,  it  is  trans- 
formed into  propionic  acid,  whilst,  when  fused  with  potash,  it  gives  acetic  and  formic 
acids. 

CROTONIC  ACIDS,  C4H602 

Isomeric  unsaturated  acids  of  this  formula  are  possible  theoretically  —  two  stereo- 
isomerides and  the  others  structural  isomerides.  The  following  acids  have  actually  been 
prepared  : 

(a)  CH2  :  CH  •  CH2  •  COOH,  vinylacetic  add  ; 

H—  C—  C02H 

(ba)          ||  ,  cis  /3-methylacrylic  acid  (solid  crotonic  acid); 

H—  C—  CH3 

H—  C—  CO2H 

(b(3)  ,  trans  /2-methylacrylic  acid  (liquid  crotonic  acid); 

CH3—  C—  H 

OH 
(c)  CH2  :  C<OyvQTT,  methylmethyleneacetic  or  a-methylacrylic  acid. 


With  the   general   formula,    C4H602,   there   corresponds   also   ethyleneacetic   or   tri- 

CH 
methylenecarboxylic  acid,    |         ^CH  •  COOH,  but   this   does  not  belong  to  the  olefine- 

CH/ 

carboxylic  acids  as  it  contains  no  double  linking,  and  it  will  therefore  be  studied  with 
the  cylic  compounds. 


CROTONIC    ACIDS  355 

(a)  VINYLACETIC  ACID,  CH2 :  CH  •  CH2  •  C02H,  has  been  prepared,  only  recently, 
by  distilling  /?-hydroxyglutaric  acid  in  a  vacuum  : 

CH2  •  C02H  CH2 

I  tt 

CH  •  OH  =      C02  +  H20  +  CH 

CH2  •  C02H  CH2  •  COfeH 

and  also  by  first  brominating  (with  bromine  dissolved  in  CS2)  allyl  cyanide,  hydrolysing 
the  product,  and  finally  removing  the  bromine  by  means  of  zinc  dust  and  alcohol,  thus : 

CH2  CH2Br  CHijBr1  CH2 

ii  '  I  L  I 

CH       — >         CHBr        — >        CHBr >         CH 

I  I  I  I 

CH9  CH9  CH,,  •      CH0 

I  I  I 

CN  CN  CO2H  C02H 

Vinylacetic  acid  is  a  very  hygroscopic  liquid,  which  solidifies  when  cooled  to  a  low 
temperature;  it  melts  at  —  39°  and  boils  at  163°.  Its  calcium  salt,  (C4H5O2)2Ca,  H2O, 
crystallises  from  water  in  shining  needles. 

When  boiled  with  5  per  cent,  sulphuric  acid  solution,  it  is  transformed  into  the  solid 
crotonic  acid,  CH2  :  CH  •  CH2  •  COOH  ->  CH3  •  CH  :  CH  •  COOH. 

This  transposition  of  the  double  linking  is  effected  also  by  boiling  with  caustic  soda 
solution,  but  in  fhis  case  a  preponderance  of  /3-hydroxybutyric  acid  is  formed  at  the  same 
time. 

H— C— C02H 

(60)  ORDINARY  or  SOLID  CROTONIC  ACID,          ||  (cis  fi-methylacrylic 

H— C— CH3 

acid  or  cis  ethylideneacetic  acid  ;  also  wrongly  known  as  u-crotonic  acid).  Its  constitution 
follows  from  its  synthesis  from  a-bromobutyric  acid  (or  rather  its  ester)  by  the  elimination 
of  HBr  under  the  action  of  alcoholic  potash  : 

CH3  •  CH2  •  CHBr  •  C02H  =  HBr  +  CH3  •  CH  :  CH  •  C02H. 

From  water  (solubility  1  in  12)  the  acid  crystallises  in  shining  needles  melting  at  71° 
to  72°;  it  boils  at  181°  to  182°,  has  an  odour  resembling  that  of  butyric  acid,  and  is  found 
free  in  crude  pyroligneous  acid.  Its  calcium  and  barium  salts  contain  no  water  of  crystal- 
lisation and  are  very  soluble  in  water. 

When  gently  oxidised  in  alkaline  solution  with  permanganate,  it  gives  aft-dihydroxy- 
butyric  acid,  CH3  •  CH(OH)  •  CH(OH)  •  C02H,  which  cannot  form  a  lactone,  so  that 
neither  of  its  hydroxyl  groups  is  in  the  y-position ;  the  double  linking  of  the  crotonic  acid 
must  hence  be  between  the  a-  and  /3-carbon  atoms.  When  halogen  hydracids  are  added 
to  it,  the  halogen  goes  to  the  /2-positiou.  With  nascent  hydrogen  it  gives  butyric  acid. 

H— C— CO2H 

(6/3)  LIQUID  CROTONIC  ACID,  ||  (trans  (3-methylacrylic  acid  or  iso- 

CH3— C— H 

crotonic  or  allocrotonic  acid  ;  known  improperly  as  /3-crotonic  acid).  This  acid  is  prepared 
from  ethyl  acetoacetate,  which,  with  PC15,  gives  probably  a  chloracetic  ester,  the  latter 
losing  a  molecule  of  HC1  and  yielding  the  two  stereoisomeric  chloroisocrotonic  acids  (or 

1  This  /8  y-dibromobulyric  acid,  when  boiled  with  water,  gives  a  fi-bromdbutyrolaclone  : 
CH2Br  CH2 0 

CHBr     =   HBr  +  CHBr 

CH2  •  COOH  CH2 CO 

Lactones  are  not  usually  formed  by  acids  brominated  in  the  a-  or  fl-position,  but  only  with 
those  where  the  bromine  atom  is  in  the  y-position.  It  may  hence  be  concluded  that  the  double 
linking  in  vinylacetic  acid  is  also  in  the  #  y-position,  since  its  brominated  derivative  gives  a 
lactone,  which  is  formed  only  when  there  is  halogen  in  the  y-position. 


356  ORGANIC    CHEMISTRY 

the  corresponding  ethyl  esters);  these  two  isomerides  may  be  separated,  the  one  formed 
in  greater  proportion  being  readily,  and  the  other  difficultly,  distilled  in  steam.  The 
latter  gives  solid,  and  the  other  liquid,  crotonic  acid  on  reduction  with  sodium  amalgam  : 

(a)    CH3  •  CO  •  CH2  •  CO  •  OC2H5  +  PC15  =  CH3  •  CC12  •  CH2  •  CO  •  OC2H5  +  POC13. 

Ethyl  acetoacetate  Intermediate  product 

(6)    CH3  •  CC12  •  CH2  •  CO  •  OC2H6  =  CH3  •  CC1  :  CH  •  CO  •  OC2H5  +  HC1. 

,  Two  stereoisomerides 

(c)    CH3  •  CC1  :  CH  •  CO  •  OC2H5  +  H2  =  CH3  •  CH  :  CH  •  CO  •  OC2H5  +  HC1. 

Ethyl  ester  of  crotonic  acid 

The  isocrotonic  acid  thus  obtained  is  liquid,  but  is  not  pure,  as  it  always  contains 
ordinary  crotonic  acid  and  a  little  tetrolic  acid,  CH3  •  C  •  C  •  C02H.  Only  within  recent 
years  (1895  and  1904)  has  it  been  separated  from  these  admixtures,  either  by  means  of 
its  sodium  salt,  which  is  more  soluble  in  alcohol,  or  by  means  of  its  quinine  salt,  which  is 
less  soluble  in  water,  than  that  of  crotonic  acid. 

After  such  purification  it  is  found  that  pure  liquid  crotonic  acid  forms  crystals  melting 
at  15-5°  and  boiling  at  169°  under  the  ordinary  pressure  or  at  74°  under  a  pressure  of 
15  mm.  The  calcium  salt,  (C4H502)2Ca,  3H20,  forms  large  prisms,  and  the  barium  salt, 
(C4H5O2)2Ba,  H20,  large  plates. 

When  heated  above  100°,  it  is  converted  partially  into  normal  crotonic  acid,  and  in 
order  to  avoid  this  change  during  distillation  the  operation  is  carried  out  in  a  vacuum  ; 
the  transformation  is  instantaneous  and  quantitative  in  presence  of  a  trace  of  bromine 
in  aqueous  solution  or  of  carbon  disulphide  under  the  influence  of  direct  sunlight. 

That  the  structure  of  isocrotonic  acid  is  the  same  as  that  of  crotonic  acid  and  not  of 
vinylacetic  acid  is  supported  by  the  fact  that  isocrotonic  acid  gives  no  lactonic  derivative 
(see  above)  and  also  by  the  fact  that  the  peroxyozonides  of  these  two  acids,  obtained  by 
Harries  and  Langheld  (1905)  by  the  action  of  ozonised  oxygen  and  having  the  structure 


CH3  •  CH  —  CH  •  C  ,  give  with  water  the  same  decomposition  products,  namely, 

|         N>:0 
0-0-0 
hydrogen  peroxide,  acetaldehyde,  and  glyoxylic  acid,  CHO  •  C02H. 

(c)  METHYLMETHYLENEACETIC  ACID  (a-Methylacrylic,  Metacrylic  or  Me- 

CH 
thylpropenoic  Acid),  CH2  :  C<Crr)3tj>  mav  ^e  obtained  by  separation  of  water  from 

a-hydroxyisobutyric  acid  and    also    by   elimination  of  a  molecule  of   HBr  from  a- 
bromoisobutyric  acid  : 

PTT 

CH3  •  CBr  •  C02H  =  HBr  +  CH2  :  C<^3H 

CH3 

This  synthesis  indicates  the  constitution  of  metacrylic  acid,  which  is  confirmed  by  the 
observation  that  reduction  of  this  acid  by  means  of  sodium  amalgam  gives  isobutyric 
acid,  this  having  a  known  constitution. 

Metacrylic  acid  crystallises  readily  from  water  in  shining  prisms  which  melt  at  +  16° 
and  boil  at  161°,  or  at  60°  to  63°  under  12  mm.  pressure.  It  has  a  strong  but  not 
unpleasant  odour  of  bad  mushrooms  and  occurs  in  Roman  chamomile  ;  it  dissolves  very 
readily  in  alcohol  or  ether.  It  exhibits  a  marked  tendency  to  polymerise,  more  especially 
at  130°,  but  also  in  the  cold  when  in  contact  with  concentrated  hydrochloric  acid.  The 
calcium  salt  forms  crystals  very  soluble  in  water. 

PENTENOIC  ACIDS,   C5H802 

Several  isomeric  pentenoic  acids  are  known,  those  which  have  been  most  closely  studied 
being  : 

(a)  ANGELIC  ACID  (a-Ethylidenepropionic,  a/3-Dimethylacrylic  or  2-Methyl-2- 

CH3—  C—  CO2H 
butenoic-i  Acid),  .      The  double  linking  in  this  acid  must  be  in  the 

CH3—  C—  H 

a  /3-position,  and  not  in  the  y-position,  since  lactonic  derivatives  are  unknown.     On 
protracted  heating  it  is  transformed  into  the  stereoisomeric  tiglic  acid. 


PENTENOIC    ACIDS  357 

Angelic  acid  was  first  found  in,  and  is  still  obtained  from,  the  roots  of  Angelica 
arcangelica,  and  occurs  as  ester  in  Roman  chamomile  oil.     The  pure  crystals  melt  at  45°, 
boil  at  185°,  and  are  only  slightly  soluble  in  water  or  volatile  in  steam. 
CH3— C— CO2H 

(b)  TIGLIC  ACID,  ||  ,  often  occurs  with  angelic  acid  and  is  formed  in  the 

H— C-CH3 

decomposition  of  various  more  complex  organic  compounds.  It  can  be  prepared 
synthetically  from  acetaldehyde  and  ethyl  a-bromopropionate  in  presence  of  zinc,  a 
hydroxy-acid  being  formed  as  an  intermediate  compound.  It  forms  transparent  crystals, 
m.-pt.  65°,  b.-pt.  198-5°,  and  is  slightly  soluble  in  cold  and  readily  in  hot  water;  it  has 
a  pleasant  smell  and  is  volatile  in  steam. 

PYROTEREBIC  ACID  (2-Methyl-2-pentenoic-5  Acid),  SJ?3>C:  CH-  CH2-  COOH, 

Lrl3 

is  formed  by  the  distillation  of  an  oxidation  product  (terebic  acid)  of  oil  of  turpentine 
(together  with  the  lactone  of  isocaproic  acid,  see  below). 

(CH3)2 :  C  •  CH(C02H)  •  CH2 

'|  |    "    =     C02  +  (CH3)2 :  C :  CH  •  CH2  •  COOH. 

O —  — CO  Pyroterebic  acid 

Terebic  (yy-dimethylparaconic)  acid 

That  pyroterebic  acid  really  has  this  constitution  is  shown  by  the  fact  that, 
on  reduction  with  hydriodic  acid,  it  gives  isocaproic  acid  of  the  known  constitution 
(CH3)2 :  CH  •  CH2  •  CH2  •  COOH.  The  position  of  the  double  linking  is  confirmed  by  the 
great  ease  with  which  it  is  converted  into  isocaproic  lactone  on  prolonged  boiling  or  by 
the  action  of  a  small  quantity  of  hydrobromic  acid  : 

(CH3)2  :  C  :  CH  •  CH2  •  COOH    ->     (CH3)2:  C— CH2— CH2 

O—      —CO 

Pyroterebic  acid  is  a  colourless  liquid  solidifying  at  —  15°  and  boiling  at  207°;  it  is 
lighter  than  water,  which  dissolves  it  with  difficulty." 

y-ALLYLBUTYRIC  ACID  (i-Heptenoic-y  Acid),  CH2  :  CH  •  [CH2]4  •  C02H,  is 
obtained  from  cycloheptanone  (or  suberone)  by  Wallaces  reaction,  passing  through  the 
oxime,  amine,  etc. : 

CH2  •  CH2  •  CH2v  CH2  •  CH2  •  CH2  •  COOH 

I    '  /C0  -*    I 

CH,j  •  CH<j  •  CHtj  CH2  •  CH  :  CH2  / 

Oycloheptanone  y-Allylbutyric  acid 

It  is  a  liquid  boiling  at  226°  and,  on  oxidation,  is  converted  into  adipic  acid, 
COOH  •  CH2  •  CH2  •  CH2  •  CH2  •  COOH. 

TERACRYLIC  ACID  (2  :  3-Dimethyl-2-pentenoic-5  Acid),  (CH3)2  :  C  :  C(CH3)  • 
CH2  .  COOH,  is  homologous  with  pyroterebic  acid  and  is  also  obtained  by  distilling  an 
oxidation  product  (terpenylic  acid)  of  oil  of  turpentine  : 

CH^  •  COjjH 
(CH3)2  :  C  •  CH  •  CH2        =  •       CO2  +  (CH3)2  :  C  :  C(CH3)  -  CH2  •  C02H. 

Teracrylic  acid 

O—    —CO 

Terpenylic  acid 

It  is  a  liquid,  b.-pt.  218°,  and  is  slightly  soluble  in  water;  with  HBr  it  forms  hepta- 
lactone,  the  y-position  of  the  double  linking  being  thus  confirmed. 

CITRONELLIC  ACID  (Dextro-rotatory),  C10H18O2.  It  has  not  yet  been  definitely 
decided  which  of  the  two  following  formulae  must  be  attributed  to  this  acid : 

\C  •  [CH2]3  •  CH(CH3)  •  CH2  •  C02H  (2  :  G-Dimethyl-l-octenoic-8  acid). 
CH/ 

S3>C  :  CH  •  [CH2]2  •  CH(CH3)  •  CH2  •  CO2H  (2  :  6-Dimethyl-2-octenoic-8  acid). 


358  ORGANIC    CHEMISTRY 

It  is  a  liquid  boiling  at  152°  under  18  mm.  pressure,  has  a  faint  odour  of  capric  acid 
and  is  obtained  by  the  oxidation  of  citronellal  (an  aldehyde,  C10H18O,  abundant  in  ethereal 
oils). 

One  of  the  two  formulae  must  be  attributed  to  Rhodinic  Acid  (laevo  -rotatory),  obtained 
by  oxidising  rhodinol,  C10H20O. 

An  inactive  i-Rhodinic  Acid  is  also  known,  this  being  obtained  by  the  reduction  (sodium 
in  amyl  alcohol)  of  geranic  acid,  (CH3)2  :  C  :  CH  •  CH2  •  CH2  •  C(CH3)  :  CH  •  C02H,  the 
hydrogen  being  added  only  at  the  a/3-double  linking. 

UNDECENOIC  ACID,  CH2  :  CH  •  [CH2]8  •  CO2H.  The  position  of  the  double  linking 
in  this  acid  is  confirmed  by  the  fact  that,  on  oxidation,  the  acid  yields  considerable  quantities 
of  Sebacic  Acid,  CO2H  •  [CH2]8  •  C02H. 

It  is  obtained  (about  10  per  cent.  )  on  distilling  castor  oil  under  reduced  pressure.  It 
forms  crystals  melting  at  24-5°  and  boils  unchanged  at  213-5°  (100  mm.).  When  reduced 
with  hydrogen  iodide,  it  gives  normal  undecoic  acid,  the  non-branched  character  of  the 
carbon  atom  chain  being  thus  proved. 

HYPOG^IC  ACID,  CH3  •  [CH2]7  •  CH  :  CH  •  [CH2]5-  CO2H,  was  formerly  thought  to 
exist  in  Arachis  hypogcea,  but  the  acid  there  present  has  been  shown  to  be  another  acid 
(arachic  acid).  It  may  be  prepared  by  fusing  stearolic  acid  with  potash,  an  intermediate 
product  with  two  double  bonds  being  probably  formed  : 

CH3  •  [CH2]7  •  C  I  C  •  [CHjg  •  CH2  •  CH2  •  CO2H  -> 

Stearolic  acid 


CH3  •  [CH2]7  •  CH  :  CH  •  [CH^  •  CH  :  CH  •  C02H  -> 

Hypothetical  intermediate  acid 

CH3  •  CO2H  +  CH3  •  [CH2]7  •  CH  :  CH  •  [CH2]5  •  C02H. 

Acetic  acid  Hypogseic  acid 

OLEIC   ACID,   C18H34O2 
(CH3  •  [CH2]7  •  CH  :  CH  •  [CH2]7  •  CO2H) 

This  acid  is  very  abundant  in  nature  in  the  form  of  glyceride  (triolein), 
especially  in  vegetable  and  animal  oils  and  fats.  After  hydrolysis  of  the  fat, 
the  fatty  acids  are  liberated  and  from  these  the  oleic  acid  separates,  as  it  is 
liquid,  whilst  the  others  are  solid.  Although  Chevreul  discovered  oleic  acid 
at  the  beginning  of  the  nineteenth  century,  it  was  only  in  1846  that  its 
composition  was  definitely  established  by  Gottlieb. 

In  the  subsequent  section  dealing  with  soap  and  candles,  the  method 
of  preparing  commercial  oleic  acid  or  "  oleine  "  on  a  large  scale  will  be  described 
in  detail;  at  the  present  juncture,  only  the  constitution  and  the  methods  of 
obtaining  pure  oleic  acid  will  be  considered.  Oils  rich  in  olein  (olive  oil,  almond 
oil,  lard,  etc.)  are  hydrolysed  with  caustic  potash  in  the  hot,  the  fatty  acids 
being  separated  from  the  transparent  soap  thus  obtained  by  means  of  hydro- 
chloric acid  ;  these  acids  are  then  heated  for  several  hours  with  lead  oxide  at 
100°,  and  the  resulting  lead  salts  dried  and  extracted  with  ether.  This  solvent 
dissolves  only  the  lead  oleate,  the  oleic  acid  being  freed  from  the  lead  by  means 
of  hydrochloric  acid.  The  oleic  acid  thus  obtained  is  purified  by  transforming 
it  into  the  barium  salt  and  crystallising  this  from  dilute  alcohol,  or  by  repeatedly 
freezing  (at  —  6°,  —  7°)  and  squeezing  the  solid  oleic  acid,  which,  when  pure, 
melts  at  14°  and  has  the  specific  gravity  0'900  in  the  liquid  state  ;  it  has  neither 
smell  nor  taste  and,  in  alcoholic  solution,  shows  no  reaction  towards  litmus. 
In  the  air  and  when  kept  for  a  long  time,  the  acid  turns  brown,  assumes  an 
acid  reaction  and  taste,  and  undergoes  partial  oxidation.  Under  a  pressure 
of  10  mm.,  it  boils  unchanged  at  223°;  it  may  also  be  distilled  without 
alteration  by  means  of  steam  superheated  at  250°. 

The  salts  of  oleic  acid  (and  of  other  high  fatty  acids)  form  the  soaps  ;  the 
alkali  salts  are  soluble  in  water  and  separable  from  this  by  salt  (NaCl),  in 


OLEIC    ACIDS  359 

saturated  solutions  of  which  they  are  completely  insoluble.  The  calcium, 
barium,  lead,  etc.,  salts  or  soaps  are  insoluble  in  water. 

The  action  of  concentrated  sulphuric  acid  is  mentioned  later  (see  Iso-oleic 
Acid). 

An  important  and  characteristic  reaction  of  oleic  acid  is  its  almost  quantita- 
tive transformation,  by  a  little  nitrous  acid  (also  by  heating  at  200°  with 
sulphurous  acid  or  sodium  bisulphite),  into  the  stereoisomeric  Elaidic  Acid, 
which  separates  from  alcoholic  solution  in  white  scales  melting  at  51°  to  52° 
and  boiling  unchanged  at  225°  under  a  pressure  of  10  mm.1 

That  these  two  isomeric  acids  have  direct  (normal)  carbon-atom  chains  is  shown  with 
certainty  by  the-  fact  that,  on  reduction  (e.  g.,  with  hydriodic  acid  and  phosphorus  or 
directly  with  hydrogen,  as  in  the  industrial  hardening  of  oils  :  see  later,  section  on  Hydrolysis 
of  Fats),  each  of  them  takes  up  two  hydrogen  atoms  giving  stearic  acid,  which  is  known  to 
have  an  unbranched  carbon-atom  chain  ;  also  with  bromine,  they  give  dibromo-derivatives 
of  stearic  acid,  and,  with  permanganate,  dihydroxyslearic  acid,  C18H34O2(OH)2.2 

ISO-OLEIC  ACID,  CjgH^Og.  With  concentrated  sulphuric  acid,  elaidic  and  oleic 
acids  give  Stearinsulphuric  Acid,  C^H^O  •  SO3H)  •  CO2H,  which,  with  hot  water,  loses 
sulphuric  acid  and  gives  hydroxy  'stearic  acid,  C^Hg^OH)  •  CO2H  (with  the  OH  at  the 
position  10).  When  distilled  under  reduced  pressure  (100  mm.)  or  with  superheated 
steam,  this  acid  loses  water  and  gives  a  considerable  quantity  of  a  white,  solid  acid  — 
iso-oleic  acid  —  which  is  readily  soluble  in  alcohol  and  slightly  so  in  ether,  from  which 
it  crystallises  in  plates,  melting  at  44°  to  45°.  The  addition  of  the  molecule  of  water  to 
oleic  or  elaidic  acid  should  take  place  at  the  central  double  linking  (provided  the  sulphuric 
acid  does  not  previously  displace  this  linking)  and  the  subsequent  separation  of  water 
should  occur  at  two  carbon  atoms  adjacent  to  the  double  linking,  so  that  the  probable 
constitution,  of  iso-oleic  acid  is,  CH3  •  [CH2]8  •  CH  :  CH  •  [CH2]6  •  C02H.  Various  facts 
are,  however,  known  which  throw  doubt  on  the  accuracy  of  this  formula. 

ACID    (2-Octadecenoic-i    Acid),    CH3  •  [CH2]14  •  CH  :  CH  •  CO2H,  is 


1  From  an  industrial  point  of  view  the  transformation  of  a  liquid  fatty  acid  into  a  solid  one 
is  of  interest,  but  this  change  is  not  utilisable  in  practice  as  it  proceeds  well  only  with  fairly 
pure  and  fresh  oleic  acid,  and  not  with  the  commercial  acid,  which  may  be  old  and  possibly 
polymerised  (see  also  later,  section  on  Hydrolysis  of  Fats). 

2  The  position  of  the  double  linking  in  the  molecule  was  under  discussion  for  a  number  of 
years,  and  until  quite  recently  this  linking  was  held  to  be  at  the  end  of  the  chain  next  the  carboxyl 
group,  i.  e.,  in  the  o  /3-position,  CH3  •  [CH2]14  •  CH  :  CH  •  COOH,  since  fusion  of  these  two  acids 
with  caustic  potash  resulted  in  the  formation  of  palmitic  acid  (Varrentrapp's  reaction,  p.  350). 
This  proof  no  longer  seemed  sufficient,  however,  when  it  was  shown  that  fusion  with  potash 
generally  displaced  the  double  bond.     On  the  other  hand,  Baruch  (1894)  succeeded  in  eliminating 
hydrogen  bromide  from  the  dibromidc  of  oleic  acid,  thus  obtaining  stearolic  acid,  which  has  a 
triple  bond  in  the  middle  of  the  molecule.     Also  the  products  of  oxidation  (by  permanganate) 
of  oleic  acid  consist  partly  of  pelargonic  and  azelaic  acids,  which  contain  nine  carbon  atoms, 
this  reaction  hence  indicating  that  the  oleic  acid  molecule  breaks  in  the  middle  of  the  chain,  at 
the  position  of  the  double  linking. 

The  most  certain  proof  of  the  constitution  of  oleic  acid  has  been  advanced  only  recently 
as  a  result  of  the  study  of  the  ozonide  of  oleic  acid  and  of  its  decomposition  products  (E.  Molinari 
and  Soncini,  1905  and  1906;  C.  Harries,  1906).  The  ozone  is  added  quantitatively  at  the 
position  of  the  double  bond  (see  p.  107),  and,  according  as  ozonised  air  (E.  Molinari)  or  ozonised 
oxygen  (Harries  )  is  employed,  so  the  simple  ozonide  : 


CH3  •  [CH2]7  •  CH  -  CH  •  [CH2]7  •  COOH 


or  a  peroxide  of  the  ozonide  : 


CH3  •  [CH2]7  •  CH—  CH  •  [CH2]7  •  C  •  OH 

I! 
O 


II 
O  -  0 


0 

is  obtained. 

Decomposition  of  these  ozonides  (of  oleic  and  elaidic  acids)  with  dilute  alkali  or  water  in 
the  hot  results  in  the  formation  of  acids  (nonoic,  azelaic,  and  others)  or  aldehydes  (nonyl  and 
semiazelaic)  with  nine  carbon  atoms,  showing  that  the  molecule  is  ruptured  at  the  position  of 
the  central  double  linking. 


360 


ORGANIC    CHEMISTRY 


prepared  by  the  removal  of  1  mol.  of  halogen  hydracid  from  the  a-halogen  derivative  of 
stearic  acid.  It  forms  white  crystals  melting  at  58°  to  59°,  does  not  take  up  ozone  in  cold 
chloroform  solution,  and  gives  palmitic  acid  when  treated  with  permanganate. 

ERUCIC  ACID  (9-Docosenoic-22  Acid),  CH3  •  [CH2]7  •  CH  :  CH  •  [CH2]n  •  CO2H,  is 
found  as  glyceride  in  the  oils  of  black  and  white  mustard,  and  in  those  of  grape-seed  and 
ravison,  from  which  it  is  readily  extracted.  It  is  obtained  crystalline  from  alcohol  in 
shining  needles  melting  at  34°,  and  boils  at  254-5°  under  a  pressure  of  10  mm. 

It  forms  a  lead  salt  soluble  in  hot  ether,  as  does  oleic  acid,  and,  like  the  latter,  it  is 
readily  transformed  into  its  stereoisomeride,  Brassidic  Acid,  by  the  action  of  a  little  nitrous 
acid  or  of  sulphurous  or  hydrobromic  acid  in  glacial  acetic  acid  solution.  This  isomeride 
crystallises  from  alcohol  in  leaflets  melting  at  65°,  and  boils  at  256°  under  a  pressure  of 
10  mm. ;  its  lead  salt  is  slightly  soluble  in  hot  ether. 

These  two  isomerides  are  not  reduced  by  sodium  amalgam,  but  with  hydriodic  acid 
they  yield  the  saturated  behenic  acid,  C22H44O2.  When  fused  with  potash,  they  give 
arachic  (C20H40O2)  and  acetic  acids.  They  yield  various  oxidation,  bromination,  and 
esterification  products.  They  have  normal  carbon-atom  chains  and  the  position  of  the 
double  linking  is  indicated  by  the  fact  that  nonoic  acid,  CH3  •  [CH2]7  •  COOH,  and  brassylic 
acid,  C02H  •  [CH2]U  •  CO2H  (and  also  a  little  arachic  acid ),  are  among  the  products  of 
oxidation  by  nitric  acid,  while  elimination  of  HBr  from  the  dibrominated  product  gives 
the  corresponding  behenolic  acid,  which  has  a  triple  bond  and  is  of  known  constitution. 

ISOERUCIC  ACID,  CH3  •  [CH2]8  •  CH  :  CH  •  [CH2]10  •  CO2H  (  ?  ),  is  obtained  by  adding 
hydrogen  iodide  to,  and  then  removing  it  from,  erucic  acid  (just  as  with  iso-oleic  acid), 
and  it  appears  that  the  double  linking  is  not  displaced  during  these  changes,  since  decom- 
position of  the  dibromide  of  this  acid  (i.  e.,  elimination  of  HBr)  gives  the  same  behenolic 
acid  as  is  given  by  erucic  acid,  while  oxidation  with  nitric  acid  also  gives  nonoic  and  brassylic 
acids.  Isoerucic  acid  should  hence  have  the  same  constitution  as  erucic  and  brassidic 
acids,  so  that,  contrary  to  theoretical  indications,  three  isomerides  would  seem  to  exist; 
this  requires  confirmation.  This"  acid  melts  at  54°  to  56°. 

B.  UNSATURATED  MONOBASIC  ACIDS   OF  THE 
SERIES,   CnH2n_402 

The  members  of  this  series  may  be  divided  into  two  groups,  as  is  the  case 
with  the  hydrocarbons  of  the  diolefine  and  acetylene  series  (see  p.  109)  :  acids 
having  a  triple  linking  (propiolic  series)  and  those  having  two  double  linkings 
(diolefine  series). 

(a)  ACIDS  WITH   TRIPLE  LINKING 
(Propiolic  or  Acetylenecarboxylic  Series) 


Name 

Constitutional  formula 

Melting- 
point 

Boiling-point 

C3H2C>2     Acetylenecarboxylic       (propiolic') 

acid      ....... 

HO  •  C  •  C02H 

9° 

83°  (50  mm.) 

0411402      Methylacetylenecarboxylic 

(tetrolic)  acid          .... 

CH3  •  0  i  C  •  C02H 

76-5° 

v203° 

C5HgO2      Ethyl-acetylenecarboxylic  acid 

C..HB  -c    c  •  CO.H 

50° 

— 

C«H8O2      Propyl- 

C3H7  -0     0  •  C02H 

27° 

125°  (20  mm.) 

C6H802      Isopropyl- 

C3H7  •  C     0  •  COjH 

38° 

115°       „ 

C7H1D02    n-Butyl- 

CiH9  -0     C  •  CO2H 

.  —  - 

135°       „ 

C7H10O2    tert.-Butyl- 

C4H9  -0      0  •  CO2H 

47° 

116°       „ 

CgH12O2    n-Amyl- 

C6HU  -0     0  •  CO2H 

5° 

149°       „ 

CjH^Ojj    n-Hexyl- 

C6H13  •  C     C  •  CO2H 

—10° 

c  . 

CwHwOjj  n-Heptyl- 

07H15  •  C     C  •  C02H 

6°-10° 

166°  (20  mm.) 

Ci2H2o02  n-Nonyl- 

C9H19  -0     0  '  CO2H 

30° 

— 

CjjHxgOjj   Dehydroundecenoic  acid 

OH  :  C  '  [CH-jg]  •  UO2H 

42-8° 

175°  (15  mm.) 

CuHigO2   Undecolic  acid 

CH8  •  C  i  C[CH2],  •  C02H 

59-5° 

— 

Ci8H82O2   Stearolic  acid 

OHS  •  [CH2],  •  C  ;  C  '  rOH2]7  •  CO2H 

48° 

CisH32O2  Tariric  acid 

CH3  '  [CH2]10  '  C  •  C  •  [CH2]4  '  CO2H 

50-5° 

— 

C^tUoOj  Behenolic  acid 

CH3  •  [CHjj]7  •  C  =  C  •  [UHJii  '  CO2H 

57-5° 

— 

PREPARATION.     These  acids  may  be  obtained  by  the  following  reactions  : 
From  a  sodium  alkyl  acetylidfe  (suspended  in  ether),  by  the  action  of  CO2 
(a)  or  of  ethyl  chloroformate  (b)  : 


PROPIOLIC    ACIDS  361 

(a)  CH3  •  C  •  C  •  Na  -f  CO2  =  CH3  •  C  :  C  •  CO2Na. 

Sodium  met.hylpropiolate 

(6)  C3H7  •  C  i  C  •  Na  +  Cl  •  CO  •  OC2H5  =  NaCl  +  C3H7  •  C  •  C  •  CO  •  OC2H5. 

Ethyl  propylacetylenecarboxylate 

Various  other  acids  of  this  series  having  the  triple  linking  at  a  distance 
from  the  carboxyl  group  (and  hence  much  more  stable  than  the  preceding, 
which,  when  heated,  lose  CO2  and  give  acetylene  hydrocarbons)  are  obtained 
by  the  elimination  of  2HBr  (by  the  action  of  alkali)  from  acids  of  the  oleic 
series,  this  reaction  being  similar  to  that  taking  place  with  unsaturated 
hydrocarbons  (see  p.  110)  : 

CH3  •  [CH2]7  •  CHBr  •  CHBr  •  [CH2]7  •  C02H  = 

Dibromide  of  oleic  acid 

2HBr  +  CH3  •  [CH2]7  •  C  :  C  •  [CH2]7  •  C02H. 

Stearolic  acid 

PROPERTIES.  Acids  of  the  type  R  •  C  !  C  '  C02H,  when  treated  with 
sodium  in  absolute  alcoholic  solution,  take  up  4  atoms  of  hydrogen,  giving 
acids  of  the  saturated  series ;  they  also  combine  easily  with  2  atoms  of  bromine, 
but  the  second  pair  of  bromine  atoms,  required  to  produce  saturation,  are 
added  only  with  difficulty  (the  action  of  light  facilitates  the  reaction) ;  when 
boiled  with  alcoholic  potash,  they  take  up  a  molecule  of  water,  forming  saturated 
/?-ketonic  acids  : 

R  •  C  !  C  •  C02H  +  H20  =  R  •  CO  •  CH2  •  C02H; 

with  aqueous  potash,  however,  they  yield  methyl  ketones,  R  •  CO  •  CH3, 
separation  of  C02  also  taking  place;  tert.-butyltetrolic  acid  does  not  react. 
The  amines  and  hydrazine  also  give  characteristic  reactions  with  these  acids. 
The  esters  of  the  acids  have  pleasant  odours  and  are  used  in  perfumes. 

Acids  with  a  triple  bond  do  not  unite  with  the  ozone  of  a  current  of  ozonised 
air  (E.  Molinari,  1907  and  1908),  but  yield  peroxyozonides  with  ozonised 
oxygen  (Harries,  1907;  seep.  359). 

PROPIOLIC  ACID  (Propinoic,  Propargylic,  or  Acetylenecarboxylic  Acid), 
CH  :  C  .  C02H,  is  obtained  by  heating  the  aqueous  solution  of  potassium  acetylene- 
dicarboxylate  : 

C  -  C02H  C  -  H 

III  =        C02+     III 

C-C02K'  C-C02K 

Propiolic  acid  is  a  liquid  with  a  more  intense  odour  than  acetic  acid;  "it  has  the  sp. 
gr.  1-139,  is  soluble  in  water,  alcohol,  or  ether,  solidifies  at  4°,  melts  at  9°,  and  distils 
unchanged  at  a  pressure  of  50  mm. 

The  alkali  and  alkaline-earth  salts  are  extremely  soluble  in  water. 

From  its  esters,  metallic  acetylides  (p.  112)  are  readily  prepared.  Under  the  action  of 
light  and  in  a  vacuum,  it  undergoes  partial  polymerisation,  yielding  benzenetricarboxylic 
acid. 

TETROLIC  ACID  (2-Butinoic  or  Methylpropiolic  Acid),  CH3  •  C  :  C  •  CO2H,  is 
obtained  by  eliminating  HC1  from  the  /3-chloro-derivative  of  crotonic  or  isocrotonic  acid. 
It  crystallises  from  water  in  rhombic  plates,  melting  at  76-5°  and  boils  unchanged  at  203°, 
but  it  distils  only  with  difficulty  in  a  current  of  steam. 

Under  the  action  of  sodium  in  alcoholic  solution  (but  not  with  sodium  amalgam  in 
aqueous  solution),  it  takes  up  hydrogen  with  formation  of  butyric  acid.  When  oxidised 
with  permanganate  in  alkaline  solution,  it  yields  acetic  and  oxalic  acids. 

DEHYDROUNDECENOIC  ACID  (i-Undecinoic-n  Acid),  HC  i  C  •  [CH2]8  •  CO2H, 
obtained  by  heating  dibromoundecenoic  acid  with  alcoholic  potash,  melts  at  42-8°.  On 
oxidation,  it  forms  sebacic  acid,  C02H  •  [CH2]8  •  C02H.  It  readily  forms  acetylides. 
Treatment  with  alcoholic  potash  at  180°  converts  it  into  the  isomeric  Undecolic 
Acid  (2-undecinoic-ll  acid),  CH3  •  C  j  C  •  [CH2]7  •  C02H,  melting  at  59-5°;  the  latter 


362  ORGANIC    CHEMISTRY 

is  hence  formed  with  the  dehydroundecenoic  acid,  if  the  reaction  referred  to  above 
takes  place  at  a  high  temperature.  Oxidation  of  undecolic  acid  yields  azelaic  acid, 
CO2H  •  [CH2]7  •  C02H ;  it  does  not  give  acetylides,  owing  to  the  absence  of  the  charac- 
teristic acetylenic  hydrogen  atom  (see  p.  110). 

STEAROLIC  ACID  (9-Octadecinoic-i  Acid),  CH3  •  [CH2]7  •  C  !  C  •  [CH2]7  •  C02H,  is 
readily  obtained  by  boiling  dibromostearic  acid  (prepared  by  brpminating  oleic  or  elaidic 
acid)  with  alcoholic  potash.  It  melts  at  48°,  and  under  the  influence  of  sulphuric  acid 
takes  up  water,  giving  a  ketostearic  acid.  When  oxidised  with  permanganate,  it  takes 
up  2  atoms  of  oxygen,  giving  diketostearic  acid,  whilst  with  nitric  acid  it  is  resolved  into 
nonoic  and  azelaic  acids  (it  is,  however,  stable  in  the  air,  and  thus  differs  from  oleic  and 
linolic  acids) : 

C  -  [CH2]7  •  CH3  CO  •  [CH2]7  •  CH3 

III  ->          1  7*    CH3  •  [CH2]7  •  C02H  +  C02H  •  [CH2]7-C02H. 

C  —  [CH2]7  •  C02H         .     CO  •  [CH2]7  •  CO2H  Nonoic  acid  Azelaic  acid 

Stearolic  acid  Diketostearic  acid 

Stearolic  acid  unites  with  2HI,  and  the  resulting  diiodostearic  acid,  when  heated  with 
alcoholic  potash,  gives  stearolic  acid  again,  but  in  two  isomeric  forms,  having  the  triple 
linking  in  the  8  to  9  and  10  to  11  positions  respectively. 

The  constitution  of  stearolic  acid  was  confirmed  by  Harries  (1907)  by  decomposing 
the  peroxyozonide  of  the  acid,  obtained  by  the  action  of  ozonised  oxygen  (ozonised  air 
does  not  yield  an  ozonide,  see  pp.  107,  359) : 

.0-C-[CH2]7.CH3 
Of    |        |  /OH       +  2H20  - 

N>  -  C  •  [CH2]7 .  C/ 

xo  =  o 

Peroxyozonide  of  stearolic  acid 

H202  +  CH3  •  [CH2]7  •  C02H  +  C02H  •  [CH2]7  •  C02H. 

Nonoic  acid  Azelaic  acid 

TARIRIC  ACID  (6-Octadecinoic-i  Acid),  CH3  •  [CH2]10  •  C  •  C  •  [CH2]4  •  CO2H,  is 
isomeric  with  stearolic  acid  and  melts  at  50-5° ;  as  glyceride,  it  forms  the  principal  com- 
ponent of  the  fat  of  the  fruit  of  Picramnia  camboita.  It  is  the  first  compound  with  a 
triple  bond  resulting  from  the  vital  process  of  an  organism.  It  is  stable  in  the  air  and 
yields  stearic  acid  on  reduction  with  hydriodic  acid,  so  that  its  molecule  contains  a  normal 
carbon  atom  chain.  Energetic  oxidation  with  permanganate  or  nitric  acid  yields  lauric 
acid,  CH3  •  [CH2]10  •  C02H,  and  adipic  acid,  CO2H  •  f  CH0]4  •  C02H. 

BEHENOLIC  ACID  (9-Docosinoic-22  Acid),  CH3  •  [CH2]7  •  C  •  [CH2]U  •  CO2H, 
melting  at  57-5°,  is  obtained  from  the  dibromide  of  erucic  or  brassidic  acid,  in  the  same 
way  as  stearolic  acid  is  formed  from  oleic  acid.  Its  constitution  follows  from  its  behaviour 
towards  reducing  and  oxidising  agents  and  from  the  transformation  of  its  oxime 
(Beckmann). 

(b)  ACIDS  WITH  TWO   DOUBLE   BONDS,   CKH2rt_4O2 
(Diolefinic  or  Sorbinic  Series) 

These  acids  are  prepared  synthetically  by  methods  analogous  to  those  used 
for  obtaining  a/?-unsaturated  acids,  for  example,  by  treating  a/3-unsaturated 
aldehydes  with  malonic  acid  in  presence  of  pyridine  : 

CH2  :  CH  •  CHO  +  CO2H  •  CH2  •  C02H  = 

Acroleln 

C02  +  H20  +  CH2 :  CH  :  CH  :  CH  •  C02H. 

/3-Vinylacrylic  acid 

The  acids  of  the  sorbinic  series,  in  which  the  two  double  linkings  are  con- 
jugated— that  is,  one  in  the  aft-  and  the  other  in  the  ^5-position  and  there- 
fore separated  by  a  simple  linking — may  be  reduced  by  sodium  amalgam  in 


DIOLEFINIC    ACIDS  363 

aqueous  solution  (in  presence  of  a  stream  of  CO2  to  fix  the  alkali ) ;  only  two 
hydrogen  atoms  are  then  added,  one  for  each  double  linking,  and  a  new  double 
linking  remains  in  the  place  of  the  simple  linking  previously  separating  the 
two  original  double  bonds  : 

X  •  CH  :  CH  •  CH  :  CH  •  C02H  +  H2  =  X  •  CH2  •  CH  :  CH  •  CH2  •  C02H. 

When  these  sorbinic  acids  are  oxidised  with  permanganate,  two  hydroxyl 
groups  enter  at  the  a/S-double  linking,  while  the  chain  is  broken  at  the  yd- 
double  linking  with  formation  of  an  aldehyde  (which  then  undergoes  oxidation) 
and  racemic  acid  : 

X  •  CH :  CH  •  CH :  CH  •  C02H  ->  X  •  CHO  +  C02H  •  CH(OH)  •  CH(OH)  -C02H. 

Racemic  acid 

When  they  are  heated  with  aqueous  ammonia,  2  mols.  of  the  latter  are 
added  at  the  double  linking  and  two  diamino-acids  formed. 

On  heating,  acids  of  the  sorbinic  series  readily  polymerise ;  hence,  when 
they  are  heated  with  lime  or  baryta,  not  only  is  C02  removed  and  diolefine 
hydrocarbons  obtained,  but  di-  and  tri-molecular  condensation  occurs,  giving 
more  complex  hydrocarbons  which  are  probably  of  cyclic  structure. 

yg-VINYLACRYLIC  ACID  (i  :  3-Pentadienoic  Acid),  CH2  :  CH  •  CH  :  CH  •  CO2H, 

is  synthesised  by  the  method  given  above.  It  forms  prisms  showing  a  grey  reflex,  and 
dissolves  slightly  in  cold  water,  but  readily  in  hot.  At  80°  it  melts  to  a  mobile  liquid, 
which,  at  100°  to  115°,  becomes  dense  and  syrupy  and  then  suddenly  decomposes  with 
evolution  of  gas.  In  carbon  disulphide  solution  it  unites  with  four  atoms  of  bromine. 

SORBINIC  or  SORBIC  ACID  (2  :  4-Hexadienoic  Acid),  CH3  •  CH  :  CH  •  CH  :  CH  • 
C02H,  occurs  in  considerable  quantities  in  mountain-ash  berries.  It  melts  at  134-5°,  boils 
at  228°  with  partial  decomposition,  is  odourless  and  dissolves  readily  in  alcohol  or  ether. 

DIALLYLACETIC  ACID  (i  :  6-Heptadiene-4-methyloic  Acid),  CH2  :  CH  •  CH2  • 
CH(CO2H)  •  CH2  •  CH  :  CH2,  is  obtained  synthetically  from  acetoacetic  acid  by  two  separate 
introductions  of  the  allyl  residue.  It  is  a  liquid,  sp.  gr.  0-950,  b.-pt.  219°  to  222°,  and  has 
an  unpleasant  smell.  Oxidation  with  nitric  acid  leads  to  the  rupture  of  the  carbon  atom 
chain  at  the  two  double  linkings  and  formation  of  tricarballylic  acid  : 


GERANIC  ACID  (2  :  6-Dimethyl-2  :  6-octadienoic-8  Acid),  (CH3)2  :  C  :  CH  •  CH2  • 
CH2  •  C(CH3)  :  CH  •  C02H,  is  obtained  either  by  oxidation  of  the  corresponding  aldehyde 
(citral)  with  silver  oxide,  or  by  elimination  of  water  from  citraloxime  by  the  action  of  acetic 
anhydride  and  hydrolysis  of  the  resulting  nitrile  with  alcoholic  potash.  It  has  also  been 
obtained,  by  a  series  of  reactions,  from  methylheptenone,  (CH3)2 :  C  :  CH  •  CH2  •  CH2  •  CO-CH3. 

It  is  a  colourless  liquid  of  not  very  pleasing  odour  and  boils  at  153°  under  a  pressure 
of  13  mm.  When  shaken  with  70  per  cent,  sulphuric  acid  it  yields,  among  other  products, 
the  isomeric  a-cyclogeranic  acid,  melting  at  106°  : 

\>    3  \/   3 

HC        CH  •  C02H  — >        H2C        CH  •  CO2H 

Hr<         r*    r*TT  IT  r<         r*    /~<TT 

2^  J™-%  *VJ  ^"3 

\C/  \rS 

\j  \j 

HTT 
2 

Geranic  acid  a-Cyclogeranic  acid 

LINOLIC  ACID,  C18H32O2.  In  the  form  of  glyceride,  this  acid  is  an  important 
constituent  of  drying  oils  (linseed,  sunflower-seed,  etc.).  From  these  oils  a  mixture  of 


364  ORGANIC    CHEMISTRY 

unsaturated  fatty  acids  may  be  obtained  which  gives  the  nitrous  acid  reaction  (solidifica- 
tion, owing  to  the  formation  of  elaidic  from  oleic  acid)  only  to  a  slight  degree ;  it  contains 
less  hydrogen,  but  not  less  carbon  than  oleic  acid,  and  is  readily  oxidised  and  thickened 
by  the  oxygen  of  the  air.  The  salts  of  these  drying  acids  are  still  more  readily  oxidisable 
than  the  acids  themselves,  and  their  lead  salts,  like  that  of  oleic  acid,  are  soluble  in  ether. 
The  various  components  of  this  mixture  of  fatty  acids — with  two  or  three  double  linkings 
— have  not  been  completely  separated,  but  as  they  fix  2  mols.  of  ozone  (Molinari  and 
Soncini,  1905),  give  a  tetrabromostearic  acid,  C18H32O2Br4,  with  bromine,  and  with  alkaline 
permanganate  yield  a  tetrahydroxystearic  (sativic)  acid,  C18H3202(OH)4,  which  gives  stearic 
acid  with  hydrogen  iodide,  the  mixture  must  contain  an  acid  with  two  double  bonds. 
This  is  linolic  acid,  C18H3202,  which  has  not  been  obtained  pure,  although  its  stereo- 
isomerides — a-Elaeostearic  Acid,  melting  at  43°  to  44°,  and  Telfairic  Acid,  obtained 
from  telfairia  oil,  m.-pt.  6°  andb.-pt.  220°  to  225°  under  13  mm.  pressure — have  been 
prepared  crystalline.  Distillation  of  ricinelaidic  acid  gives  a  further  isomeride,  which 
has  a  normal  structure,  contains  two  double  linkings,  and  melts  at  53°  to  54°. 

(c)  ACIDS  WITH  THREE  DOUBLE   BONDS,   CBH2n_6O2 

CITRYLIDENEACETIC  ACID  (2  :  6-Dimethyl  -2:6:  8-decatrienoic-io  Acid), 
CH3  •  C(CH3)  :  CH  •  CH2  •  CH2  •  C(CH3)  :  CH  .  CH  :  CH  .  C02H,  is  a  mobile  oil,  distilling 
at  175°  under  a  pressure  of  18  mm.,  and  is  formed  by  condensing  1  mol.  of  citral  with  1 
mol.  of  malonic  acid  in  presence  of  pyridine  : 

CH3  •  C(CH3) :  CH  •  CH2  •  CH2  •  C(CH3) :  CH  •  CHO  +  C02H  •  CRj  •  CO2H  = 

Citral  Malonic  acid 

H20+C02+C12H1802. 

Oitrylideneacetic  acid 

LINOLENIC  AND  ISOLINOLENIC  ACIDS,  C18H30O2,  are  components  of  the 
mixture  of  drying  acids  referred  to  above,  but  have  not  yet  been  isolated  in  a  pure  state. 
With  bromine,  however,  two  hexabromostearic  acids,  C18H30O2Br6,  and  with  permanganate 
two  hexahydroxystearic  acids,  C18H3002(OH)C,  have  been  obtained,  and  these  must  be  derived 
from  two  acids  containing  three  double  bonds.  The  fatty  acids  of  linseed  oil  contain 
50  per  cent,  of  these  two  acids,  together  with  linolic  and  oleic  acids,  whilst  the  other  drying 
oils  contain  linolic  acid  in  preponderating  amount. 

The  constitution  of  Linolenic  Acid  was  definitely  established  by  E.  Erdmann, 
Bedford,  and  Raspe  (1909)  by  decomposing  the  corresponding  tri-ozonides.  The  three 
double  bonds  occur  in  a  normal  chain  : 

CH3  •  CH2  •  CH  :  CH  •  CH2  •  CH  :  CH  •  CH2  •  CH  :  CH  •  [CH2]7  •  C02H. 

The  ozonides  of  two  stereoisomerides  were  prepared,  their  products  of  decomposition 
being  :  propaldehyde,  malonic  dialdehyde,  and  azelaic  semialdehyde. 

Fish  oil  contains  another  isomeride,  Jecorinic  Acid,  C18H30O2,  which  has  been 
little  studied. 

III.  POLYBASIC  FATTY  ACIDS 
A.   SATURATED   DIBASIC   ACIDS,    CnH2n(CO2H)2 

These  acids  are  dibasic,  since  they  contain  two  carboxyl  groups  and  form 
two  series  of  derivatives  :  acid  and  normal. 

In  general  they  are  crystalline  substances,  which  distil  unchanged  in  a 
vacuum  (beyond  C3)  and  are  soluble  in  water.  The  members  with  even 
numbers  of  carbon  atoms  have  lower  melting-points  than  their  immediate 
neighbours  in  the  series  with  odd  numbers  of  carbon  atoms,  and  the  differences 
thus  shown  diminish  as  the  number  of  carbon  atoms  increases.  The  solu- 
bility in  water  is  greater  with  the  acids  containing  an  odd  number  of  carbon 
atoms  than  for  the  others,  and  in  both  cases  it  diminishes  with  increase  of 
molecular  weight.  The  dissociation  constant  is  very  high  for  oxalic  acid, 
and  diminishes  considerably  in  the  higher  homologues,  which  are  hence  less 
energetic  acids. 


DIBASIC    ACIDS 

TABLE  OF  THE  NORMAL  SATURATED  DIBASIC  ACIDS 


365 


Empirical 
formula 

Name 

Structural  formula 

Melting-point 

C2H204 

• 

Oxalic  acid          .... 

COOH  •  COOH 

189°  (anhyd.) 

C3H404 

Malonic  ,, 

C02H  •  CH2  •  CO2H 

132° 

C4H604 

Succinic  „            .... 

C02H  •  [CH2]2  •  CO2H     182° 

C5H804 

Glutaric  „            .... 

CO2H  •  [CH2]3  •  C02H 

97-5° 

C6H10°4 

Adipic     ,',            .         . 

C02H  •  [CH2]4  •  CO2H 

149° 

C7H12O4 

Pimelic  „ 

C02H  •  [CH2]5  •  CO2H     103° 

C8H14O4 

Suberic   „            .... 

C02H  •  [CH2]6  •  OC2H     141° 

C9H16°4 

Azelaic    „            .... 

C02H  •  [CH2]7  •  C02H     106° 

C10H18°4 

Sebacic   „ 

C02H  •  [CH2]8  •  C02H     133° 

C12H22°4 

Decamethylenedicarboxylic  acid   . 

C02H  •  [CH2]10  •  C02H    125° 

C13H24°4 

Brassylic  acid     .... 

C02H  •  [CH2]U  •  CO2H    112° 

C14H26°4 

Dodecamethylenedicarboxylic  acid 

C02H  •  [CH2]12  •  C02H    123° 

C17H32°4 

Roccellic  acid      .... 

C02H  •  [CH2]15  •  C02H    132° 

METHODS  OF  PREPARATION.  In  addition  to  the  usual  methods  of 
oxidising  monobasic  fatty  acids,  primary  hydroxy-acids,  alcohols,  and  glycols, 
an  important  and  general  method  consists  in  hydrolysing  the  nitriles  (see 
p.  238)  or  cyano-derivatives  of  the  acids,  these  being  obtained  from  halogen 
alkyls  with  a  less  number  of  carbon  atoms. 

Dibasic  acids — always  of  higher  molecular  weight — are  also  obtained  by 
the  condensation  of  2  mols.  of  the  esterified  monopotassium  salt  of  a  lower 
dibasic  acid  by  electrolysis  of  Hofer's  apparatus  : 


CH2  •  COOC2H5 


CH2  *  COOK 


CH2  • COOK 


CH,  •  COOC9Hfi 


H  •  OH 
H  •  OH 


CH, 


COOC2H5 


CH2  •  COOC2H5  CH2 

2  mols.  Potassium  ethyl  succinate  Ethyl  adipate 

PROPERTIES.  The  constitution  is  deduced  from  the  synthesis  in  which 
compounds,  especially  the  nitriles,  of  known  constitution  are  employed. 
Structural  isomerism  commences  with  the  acids  containing  four  carbon  atoms. 
Those  acids  which  have  the  two  carboxyls  united  to  different  carbon  atoms 
(i.  e.,  other  than  oxalic  and  malonic  acids  and  their  derivatives),  in  presence 
of  dehydrating  substances  (PC15,  COC12,  etc.),  or  on  heating,  lose  a  molecule  of 
water  and  form  a  kind  of  cyclic  compound,  known  as  an  internal  anhydride  : 


CH2  • COOH 
CH2  • COOH 

Succinic  acid 

CH2  • COOH 

CH2 

CH2  •  COOH 

Glutaric  acid 


CH  •  CO 


H20 


=  H20 


. 

|  >0 

CH2—  COX 

Succinic  anhydride 

CH2—  CO 
CH      O 


CH2— CO 


Glutaric  anhydride 

The  ready  formation  of  these  anhydrides  by  the  reaction  of  the  two  terminal 
carboxyl  groups  («,  a/)  is  readily  explained  by  arranging  the  carbon  atoms 


366 

in  space  (see  pp.  19  et  seq.),  with  their  valencies  in  the  directions  of  the  angles 
of  regular  tetrahedra.  Thus,  with  succinic  acid,  which  contains  four  carbon 
atoms,  the  two  hydroxyls  of  the  carboxyl  groups  are  found  to  be  moderately 
close  together  (Fig.  251),  whilst  in  glutaric  acid  the  two  hydroxyls  are  almost 
superposed,  so  that  water  readily  separates,  forming  a  closed  ring  (Fig.  252). 

Similarly  the  amides   (which  see)  or  the  ammonium  salts  of  these  acids 
readily  form  imides  (see  later),  which  may  be  hydrolysed  like  the  amides  : 

CH2  •  COONH4  CH2  •  C(\ 

=    2H20+     |  >NH 

CH2  •  COOH  CH2  •  COT 

Monoammonium  succinate  Succinimide 

COOH 
-  OXALIC  ACID  (Ethandioic  Acid),  |  ,  has  been  known  from  the 

COOH 
earliest  times,  since  it  occurs  frequently  in  nature  in  plants,  especially  in 


FIG.  251.  FIG.  252. 


sorrel,  in  the  form  of  acid  potassium  oxalate,  and  also  as  incrustations  of  calcium 
oxalate  in  plant-cells  and  in  the  roots  of  rhubarb. 

It  is  often  formed  in  the  oxidation  of  organic  substances  (sugar,  wood, 
starch,  etc.)  by  nitric  acid  or  permanganate,  orl)y  fused  caustic  potash. 

It  is  obtained  synthetically  by  heating  sodium  or  potassium  formate 
rapidly  (best  in  a  vacuum  at  280°)  :  2H  •  COONa  =  Na2C204  -j-  H2  (the 
reverse  change,  from  oxalic  to  formic  acid,  has  already  been  referred  to  on 
p.  324),  or  by  passing  carbon  dioxide  over  metallic  sodium  heated  to  about 
350°  :  2Na  +  2C02  =  Na2C204. 

Its  industrial  manufacture  was,  until  recently,  carried  out  exclusively 
by  the  method  devised  by  Gay-Lussac  in  1829  and  applied  by  Dale  in  1856  : 
sawdust  (1  part)  moistened  with  caustic  potash  solution  (2  parts,  sp.  gr.  1'4) 
or  a  mixture  of  4  parts  of  KOH  and  6  parts  of  NaOH  is  heated  at  about  240° 
and  frequently  stirred  on  iron  plates  until  a  greenish-yellow  mass  is  formed. 
While  still  hot,  this  is  dissolved  in  water  and  the  solution  filtered  and  con- 
centrated to  38°  Be.  When  cold,  the  solution  deposits  crude  sodium  oxalate, 
which  is  dissolved  in  a  small  quantity  of  boiling  water  and  precipitated  as 
insoluble  calcium  oxalate  by  means  of  lime.  The  precipitate  is  made  into  a 
paste  with  water  and  the  oxalic  acid  liberated  by  addition  of  sulphuric  acid. 
The  liquid  is  decanted  and  concentrated  until  the  whole  of  the  calcium  sulphate 


•  OXALIC    ACID  367 

separates,  the  oxalic  acid  being  then  allowed  to  crystallise  out  and  subsequently 
purified  by  repeated  recrystallisation.  When  sugar  (saccharose)  is  obtainable 
at  a  very  low  price,  it  may  be  oxidised  with  nitric  acid  (sp.  gr.  T4)  in  the  cold 
in  presence  of  O'l  per  cent,  of  vanadic  oxide,  V2O5,  but  for  the  process  to  pay, 
the  nitrous  vapours  evolved  must  be  recovered  for  the  regeneration  of  the 
nitric  acid.  From  100  kilos  of  sugar  140  kilos  of  oxalic  acid  may  be  obtained, 
while  Molinari  and  Fedeli  (1914)  obtained  more  than  160  kilos  of  the  acid 
(see  also  Naumann,  Moeser,  and  Lindenbaum's  Ger.  Pat.  183,022,  1907,  and 
Ger.  Pat.  208,999). 

At  the  present  time,  the  acid  and  also  the  various  alkaline  oxalates  are 
prepared  by  Goldschmidt's  process  (see  p.  324),  which  consists  in  heating  a 
mixture  of  potassium  or  sodium  formate  with  a  little  potassium  carbonate 
in  presence  of  a  small  proportion  of  potassium  oxalate  and  a  slight  excess  of 
alkali  (3  to  4  per  cent. ).  According  to  Ger.  Pat.  229,853  of  1908  about  30  parts 
of  sodium  formate  and  0'3  part  of  borax  or  boric  acid  are  heated  together 
at  400°  in  an  iron  vessel  and  well  stirred  for  thirty  to  forty  minutes.  Another 
method  of  manufacture  (Fr.  Pat.  413,947,  1910)  consists  in  allowing  the  formate 
to  fall  into  an  empty  pot  maintained  at  550°  to  600°  by  means  of  a  metal-bath ; 
if  the  temperature  of  the  mass  introduced  is  kept  for  half  an  hour  above  400° 
the  formate  is  converted  almost  quantitatively  into  pulverulent  oxalate  (150 
kilos  per  sq.  metre  of  heated  surface);  see  also  Kirchner's  Ger.  Pat.  269,833, 
1914.  From  the  oxalate  thus  obtained  the  oxalic  acid  is  liberated  by  means 
of  sulphuric  acid  (see  above) ;  the  final,  somewhat  impure  mother-liquors  may 
be  utilised  to  make  iron  oxalate,  which,  on  calcination,  yields  an  excellent 
English  red. 

PROPERTIES.  Oxalic  acid  crystallises  in  odourless,  colourless,  trans- 
parent prisms,  H2C2O4  -f-  2H20,  which  have  a  marked  acid  taste,  effloresce 
in  the  air,  and  have  the  sp.  gr.  1*64.  The  solubility  at  various  temperatures, 
expressed  as  grams  of  the  acid  dissolving  in  100  grams  of  water,  is  as  follows  : 

Temperature  .       0°       10°      20°      30°      40°      50°      60°        70°        80°        90° 
Solubility        .    5-2          8     13-9        23        35     51-2        75     117-7     204-7        345 

The  crystals  lose  their  water  of.  crystallisation  partly  at  30°  and  completely 
at  110°  to  120°,  but  melt  at  99°  in  the  residual  water;  the  anhydrous  acid 
melts  and  decomposes  at  187°  and  sublimes  at  a  higher  temperature.  When 
heated  moderately  strongly  or  treated  with  concentrated  sulphuric  acid,  oxalic 
acid  decomposes  into  CO,  C02,  and  H20.  It  is  somewhat  poisonous. 

USES.  It  is  used  in  the  dyeing  and  printing  of  woollen  textiles  and  yarns ; 
it  serves  for  bleaching  straw,  removing  rust  stains  from  fabrics,  purifying 
glycerine,  stearine,  tartaric  acid,  and  cream  of  tartar  from  the  last  traces  of 
lime,  cleaning  brass,  etc.  To  some  extent  it  is  used  for  the  manufacture,  by 
electrolytic  reduction,  of  glycollic  acid  (see  later),  which  is  used  in  dyeing  and 
printing  textiles.  Large  quantities  of  the  acid  are  used  for  the  extraction  of 
rare  earths  from  monazite  (see  Vol.  I.,  p.  504). 

STATISTICS  AND  PRICES.  Commercial  crystallised  oxalic  acid  1  was  sold  before 
the  war  at  28s.  to  30s.  per  cwt.,  while  the  purified  acid  cost  40s.,  and  the  chemically  pure 
64s.  During  the  war  the  price  rose  to  £20. 

The  Italian  imports  of  oxalic  acid  are  as  follows  : 

1  Testing  of  Oxalic  Acid.  The  acid  is  estimated  by  means  either  of  normal  caustic 
soda  solution  in  presence  of  phenolphthalein,  or  of  decinormal  potassium  permanganate  solution 
in  presence  of  sulphuric  acid  in  the  hot : 

2KMn04  +  5H2C2O4  +  3H.J304  =  K2S04  +  10C02  +  8H20  +  2MnS04. 

Ammoniacal  impurities  are  detected  with  Nessler's  reagent  (Vol.  I.,  p.  690),  and,  when  pure, 
the  acid  should  leave  no  ash,  and  0-5  gram  of  it  should  dissolve  completely  when  shaken  with 
100  c.c.  of  ether. 


368  ORGANIC    CHEMISTRY 

1908  1910  1912  1913  1914  1915  1916  1917  1918 

Cwts.  .   1,920      3,780      5,470      5,784      4,104      2,452       1,184        2,958       1,788 
Value  £    —         6,424        —          8,097        —         8,582        —         50,286          — 

The  United  States  imported  1650  tons  of  oxalic  acid  in  1911  and  1800  tons  in  1913. 

In  Russia,  four  factories  produced  about  850  tons  of  oxalic  acid  in  1909,  by  heating 
sawdust  with  alkali.  In  1908  Germany  exported  5100  tons  of  oxalic  acid  and  potassium 
oxalate,  4470  tons  (£128,000)  in  1909,  5015  tons  in  1911,  and  5693  tons  in  1913. 

SALTS  OF  OXALIC  ACID.  Owing  to  the  presence  of  two  carboxyl  groups  in  the 
molecule,  oxalic  acid  gives  both  acid  and  neutral  salts.  The  alkaline  oxalates  are  soluble 
in  water  and  are  often  used  instead  of  the  acid,  especially  in  dyeing. 

NORMAL  POTASSIUM  OXALATE,  K2C2O4,  used  to  be  obtained  by  neutralising 
the  acid  with  potassium  carbonate,  concentrating  and  allowing  to  crystallise.  Nowadays 
it  is  prepared  by  Goldschmidt's  method  (see  above).  It  dissolves  in  three  parts  of  water, 
crystallises  with  1H20,  and  readily  effloresces  in  the  air.  It  costs  42s.  to  44s,  per  cwt., 
or,  when  chemically  pure,  £3. 

ACID  POTASSIUM  OXALATE  (or  Potassium  Hydrogen  Oxalate),  KHC2O4,  is 
obtained  by  dissolving  the  neutral  oxalate  (1  mol.  )  and  oxalic  acid  (1  mol.)  in  water, 
concentrating  and  allowing  to  crystallise,  when  it  separates  with  1H2O.  It  has  a  bitter, 
acid  taste,  is  poisonous,  and  dissolves  in  14  parts  of  hot  water. 

POTASSIUM  TETROXALATE  (Commercial  Salt  of  Sorrel),  KHC2O4  -f  H2C2O4  -f 
2H20,  does  not  effloresce  or  lose  its  water  of  crystallisation  in  the  air.  It  is  obtained  by 
mixing  a  hot,  saturated  solution  of  potassium  oxalate  with  the  calculated  amount  of 
saturated  oxalic  acid  solution.  It  costs  42s.  to  44s.  per  cwt.,  or,  if  chemically  pure,  64s. 

CALCIUM  OXALATE,  CaC2O4,  crystallises  with  2H20  and  is  obtained  from  a  solution 
of  a  soluble  oxalate,  containing  either  ammonia  or  acetic  acid,  by  addition  of  a  soluble 
calcium  salt.  It  is  insoluble  in  water  or  acetic  acid. 

FERROUS  OXALATE,  FeC2O4,  or,  better,  Ferrous  Potassium  Oxalate, 
K2Fe(C2O4)2  +  H2O,  gives  a  yellow  aqueous  solution  owing  to  the  colour  of  its  cation, 
FeC2O4".  It  possesses  strong  reducing  properties  and  is  largely  used  on  this  account, 
while  it  serves  also  as  a  good  photographic  developer. 

POTASSIUM  FERRIC  OXALATE,  K2Fe3(C2O4)3,  gives  a  green  aqueous  solution 
owing  to  the  colour  of  its  cation,  Fe(C2O4)3'".  In  the  light  it  yields  C02  and  potassium 
ferrous  oxalate,  and  it  is  used  in  the  platinotype  method  of  photography. 

CO  H 
MALONIC  ACID  (Propandioic  Acid),  H4C304  or  CH2<^2^>  forms  crystals  melting 

at  132°  and  is  readily  soluble  in  water  (1  :  14  at  15°),  alcohol,  or  ether.  It  occurs  in  the 
beetroot  and  is  obtained  synthetically  by  hydrolysing  cyanoacetic  acid  prepared  from 
a  hot  aqueous  solution  of  potassium  chloroacetate  and  potassium  cyanide  : 


Ohloroacetic  acid  Cyanoacetic  acid  Malonic  acid 

Like  all  compounds  containing  two  carboxyl  groups  united  to  the  same  carbon  atom, 
it  evolves  CO2  when  heated  above  its  melting-point,  acetic  acid  being  formed.  Higher 
monobasic  acids  are  similarly  obtained  from  alkylated  malonic  acids  . 

CH3  .  CH2  •  CH2  •  CH<^H  =  co^  +  CHg  .  CHg  .  ^  .  ^  .  CQ^ 

Normal  propylmalonic  acid  Normal  valeric  acid 

ro    r  H 

Malonic  acid  forms  an  ester,  ETHYL  MALON  ATE,  CH2<::r  2  '  :&**,  which  is  of  great 

cu2  •  L2±±5 

importance,  since  it  allows  of  the  synthetical  preparation  of  the  most  varied  higher  dibasic 
acids,  and  from  these,  by  loss  of  carbon  dioxide,  of  the  corresponding  monobasic  acids. 
This  ester  is  obtained  by  passing  gaseous  hydrogen  chloride  into  cyanoacetic  acid  dissolved 
in  absolute  alcohol  ;  it  is  then  separated  by  distillation,  as  it  boils  at  198°.  At  15°  it 
has  the  sp.  gr.  1-061. 

The  hydrogen  atoms  of  the  methylene  group  of  this  ester  may  be  replaced  by  one  or 
two  atoms  of  sodium  (or  halogens  )  giving  highly  reactive  sodiomalonic  esters.  The  sodium 
in  these  may  be  substituted  by  one  or  two  alkyl  groups  simply  by  treatment  with  an  alkyl 
iodide,  sodium  iodide  being  separated  at  the  same  time.  The  resulting  products  are 


ETHYL  MALONATE  SYNTHESES 


369 


higher  homologues  of  the  malonic  ester,  and  hence  yield  the  corresponding  homologues 
of  malonic  acid  on  hydrolysis.  The  hydrolysis  of  the  esters  of  dibasic  acids  by  alkali 
takes  place  in  two  stages,  the  second  ester  group  being  hydrolysed  more  slowly  than  the 
first. 

HOMOLOGUES   OF  MALONIC  ACID 


Name  of  acid 

Formula 

Melting- 
point 
of  acid 

Boiling-point 
of  the 
diethyl  ester 

Methylmalonic 

CH3-CH(C02H)2 

about  130° 

190°-193° 

Dimethylmalonic     . 

(CH3)2:C(C02H)2 

192°-]  93° 

196° 

Ethylmalonic 

C2H5-CH(C02H), 

112° 

210° 

Diethylmalonic 

(C2H5)2:C(C02H)2 

124° 

2306 

Propylmalonic 

C2H5-CH2-CH(C02H)2 

93-5° 

219°-222° 

Dipropylmalonic 

(CaH5.CH2)2:C(C02H)2 

156° 

248°-250° 

Isopropylmalonic 

(CH3)2:CH-CH(C02H)2 

86° 

213°-214° 

Methylethylmalonic 

(CH3)(C2H5)C(C02H)2 

118° 

207°-208° 

Butylmalonic 

C2H5-CH2-CH2-CH(C02H)2 

98-5° 

— 

sec.  Butylmalonic    . 

C2H5.CH(CH3)-CH(C02H)2 

76° 

224°-225° 

Isobutylmalonic 

(CH3)2:CH-CH2.CH(C02H)2 

107° 

225°-226° 

Diisobutylmalonic   . 

[(CH3)2:CH-CH2]2C(C02H)2 

145°-150° 

245°-255° 

Methylpropylmalonic 

(CH3)(C2H5-CH2)C(C02H)2 

106°-107° 

220°-223° 

Methylisopropylmalonic   . 

[(CH3)2CH](CH3):C(C02H)2 

124° 

221° 

Pentylmalonic 

C2H5  •  CH2  •  CH2  •  CH2  •  CH(C02H)a 

82° 

— 

Tsoamylmalonic       .         .      (CH3),CH  •  CH2  •  CH2  •  CH(CO2H)2 

98° 

240°-242° 

Diisoamylmalonic    . 

[(CH3)2CH  •  CH2  •  CH2]2C(C02H)2 

147°-148° 

278°-280° 

2-Methylbutylmalonic 

(CH3)(C2H5)CH  •  CH2  •  CH(C02H)2 

90°-91° 

244°-246° 

tert.  Amylmalonic  . 

(CH3)2(C.H5)C  •  CH(C02H)2 

— 

238° 

sec.  Amylmalonic    . 

(C2H5)2CH-CH(C02H)2 

52°-53° 

242°-245° 

Methyliso  butylmalonic 

(CH3)2CH  -€H2  •  C(CH3)(C02H)2 

122° 

230°-235° 

Ethylisopropylmalonic 

(CH3)2CH-C(C2H5)(C02H)2 

131°-131-5° 

232°-233° 

Cetylmalonic  . 

CH3.[CH2]15-CH(C02H)2 

121-5°-122° 

— 

Dicetylmalonic 

[CH3-(CH2)15]2:C(C02H)2 

86°-87° 

— 

Dioctylmalonic 

[CH3-(CH2)7]2:C(C02H). 

75° 

338°-340° 

Treatment  of  ethyl  malonate  (1  mol.)  with  sodium  (1  or  2  atoms)  results  in  the  evolu- 
tion of  hydrogen  and  the  formation  of  the  solid  mono-  or  di-sodiomalonic  ester  : 


The  sodium  of  the  monosodio-compound  may  be  replaced  by  an  alkyl  group  and  the 
remaining  methylene  hydrogen  then  replaced  by  sodium,  which  may  subsequently  be 
substituted  by  an  alkyl  group  different  from  the  first. 

An  example  of  this  synthesis  is  as  follows  (see  also  later  :  Glutaric  Acid)  : 


Na 


' 


CH3I  =  Nal 


CH 


C2H5 


CH 


C2H5I  «  Nal 


CH 


Hydrolysis  of  the  final  ester  yields  Methylethylmalonic  Acid. 
Homologues  of  succinic  acids  may  be  obtained  as  follows  : 


*2  '  C2H5 


Ethyl  sodiomethylmalonate 


NaBr  +  CH- 


Ethyl  a-bromopropionate 


C02-C2H5 


C2H5 


COC 


VOL.  II. 


24 


370  ORGANIC    CHEMISTRY 

When  this  complex  ester  is  saponified  and  the  acid  thus  formed  heated  to  expel  CO., 
from  one  of  the  carboxyl  groups  united  to  the  same  carbon  atom,  symmetrical  dimethyl- 
succinic  acid  is  obtained  : 


C02H  CO2H    CO2H 


Also  2  mols.  of  ethyl  sodiomethylmalonate  (or  ethyl  sodiomalonate  or  its  homologues) 
may  be  condensed  in  ethereal  solution  by  means  of  bromine  or  iodine  : 

C02-C2H6C02-C2H5 

r*n    -P  TT 
2CH3  •  CNa<^2  '^  +  I2  =  2NaI  +  CH3  •  C  -         -  C  •  CH3 

C02.C2H5C02.C2H5 

Ethyl  dimethylethanetetracarboxylate 

Hydrolysis  of  this  ester  gives  the  corresponding  acid  and  the  latter  loses  2C02  on  heat- 
ing, yielding  dimethylsuccinic  acid.  Similarly  succinic  acid  may  be  obtained  from 
ethyl  sodiomalonate,  and  homologous,  symmetrical  alkylsuccinic  acids  by  condensing 
2  mols.  of  ethyl  sodioalkylmalonate  containing  alkyl  groups  higher  than  methyl  : 

CO,H     C09H  CO..H    CO,H 

r    r  i  '    r 

CH3  •  C  -  C  •  CH3  =  2C02  -j-  CH3  •  CH  -  CH  •  CH3 

Dimethylsuccinic  acid 

C02H     C02H 

SUCCINIC   ACIDS,   C4H6O4  (Two  Isomerides) 

(a)  ORDINARY  SUCCINIC  ACID  (Butandioic  or  Ethylenesuccinic  Acid), 
C02H  •  CH2  •  CH2-  CO2H,  occurs  in  nature  in  various  plants,  in  the  unripe  grape,  in  certain 
lignites,  and,  more  especially,  in  amber,  from  which  it  is  obtained  by  distillation  or 
fermentation.1 

Alcoholic  fermentation  also  yields  a  small  amount  of  succinic  acid,  which  thus  forms 
a  normal  constituent  of  wine.  Ehrlich  (1909)  has  shown  that,  in  the  alcoholic  fermenta- 
tion of  sugar,  the  succinic  acid  is  formed  from  the  glutamic  acid  resulting  from  the 
decomposition  of  the  cells  of  the  ferment.  Numerous  syntheses  also  lead  to  the  formation 
of  succinic  acid;  e.  g.,  the  reduction  by  hydrogen  of  fumaric  or  maleic  acid,  these  being 
unsaturated  dibasic  acids,  C4H4O4  ;  hydrolysis  of  ethylene  cyanide,  CN  •  CH2  •  CH2  •  CN, 
obtained  from  ethylene  bromide,  C2H4Br2  (see  above);  reduction  of  the  hydro  xy-acids, 

1  Amber  is  found  on  the  shores  of  Denmark  and  along  the  coast  of  the  Baltic,  in  the  neigh- 
bourhood of  Konigsberg,  Holstein,  and  Mecklenburg,  in  Finland,  Siberia,  and  the  Urals  (  Jekater- 
inenberg  ),  and  rarely  in  Sicily  and  Spain.  It  consists  of  fossil  resins  (succinite,  allingite,  beckerite, 
glessite,  geclanite,  etc.).  That  thrown  up  on  to  the  seashore  is  transparent,  shiny,  yellowish, 
pale  (gedanite  and  succinite)  or  yellowish  -brown  (beckerite  and  stantienite  ),  while  that  mined 
is  covered  with  an  opaque,  hard  crust.  It  is  odourless  and  tasteless,  and  when  rubbed  with  a 
cloth  becomes  electrified.  It  is  insoluble  or  almost  so  in  ether,  cold  alcohol  and  other  ordinary 
solvents,  but  it  gradually  dissolves,  to  the  extent  of  30  per  cent.,  in  boiling  alcohol  ;  in  chlor- 
hydrin  it  dissolves  somewhat  and  turns  brown.  By  boiling  alkalies  it  is  partially  saponified. 
It  softens  and  swells  at  150°  to  180°,  melts  at  250°  to  300°,  and  dry-distils  at  above  400°,  giving 
succinic  acid  and  yellow  amber  oil  (of  repulsive  smell;  sp.  gr.  0-95;  soluble  in  alcohol,  ether  or 
petroleum  ether;  used  for  varnishes)  and  leaving  a  residue  termed  amber  colophony,  used 
for  making  varnishes.  Amber  has  the  sp.  gr.  1-050  to  1-090,  the  acid  value  15  to  34, 
the  saponification  number  86  to  150,  and  the  iodine  number  57  to  58.  It  consists  of  70  per 
cent,  of  the  succinic  ester  of  succinoresinol  and  28  per  cent,  of  abietinsuccinic  acid;  some- 
times it  contains  a  little  sulphur  (succinite).  It  is  sometimes  adulterated  with  copal  resin  (which 
is,  however,  soluble  in  various  solvents).  An  excellent  substitute  for  it  is  baekelite  (see  Phenol). 
Amber  is  used  for  ornaments,  especially  for  the  mouthpieces  of  pipes  and  cigar-holders.  Scrap 
amber  is  either  distilled,  or  used  for  making  varnish,  or  softened  in  the  hot  with  carbon  disulphide 
and  pressed,  or  pressed  directly  at  200°  under  400  atmospheres'  pressure  to  make  block  amber. 
The  output  in  Prussia  before  the  war  was  400  to  450.  tons  per  annum.  Italy  imported,  before 
the  war,  300  to  400  kilos  per  year  at  a  price  varying  from  £2  to  £12  per  kilo. 


SUCCINIC    ACIDS 


371 


malic  and  tartaric  acids,  by  means  of  hydriodic  acid  ;  heating  of  ethyl  ethanetricarboxylate 
above  its  melting-point  : 


CO^H 


Various  alkylsuccinic  acids  are  obtained  by  syntheses  with  ethyl  malonate. 


HOMOLOGUES   OF   SUCCINIC  ACID 


Kama  of  Acid 

Composition 
of  acid 

V-'-'     --•   -.'-  - 

of  acid 

Melting  point  of 
1     the  anhydride 

^ 

Methylsuccinic           ..... 

C5HA 

112° 

37° 

Ethylsuccinie  ...... 

CgH10O4 

99° 

Liquid 

symm.  Dimethylsuccinic  (fumaroid)  . 

C6H10O4 

209° 

43° 

„                    „               (maleinoid)  . 

C6H1004 

129° 

91° 

asymm.             „                 .... 

CjHjA 

140°-141° 

31° 

Propylsuccinic           ..... 

C7H12O4 

91° 

Liquid 

Isopropylsuccinic      ..... 

CjHu04 

114° 

„ 

symm.  Methylethylsuccinic  (fumaroid) 

C^A 

180° 

— 

„                        „                 (maleinoid) 

C^BjA 

101°-102° 

Liquid 

asymm.                 „                        ... 

C^HjA 

104° 

„ 

Trimethylsuccinic     ..... 

C7H1204 

152° 

38° 

Butylsuccinic  ...... 

CgH14O4 

81° 

— 

Isobutylsuccinic        ..... 

CgHjA 

109° 

•    Liquid 

symm.  Methylpropylsuccinic  (fumaroid) 

CgH14O4 

158°-160° 

„ 

„                       „                  (maleinoid)     . 

CgHjA 

92°-93° 

„ 

„      Methylisopropylsuccinic  (fumaroid) 

CgHjA 

174°-175; 

46° 

„                      „                        (maleinoid) 

CgH14O4 

125°-126° 

Liquid 

„      Diethylsuccinic  (fumaroid) 

CgH14O4 

189°-190° 

„ 

„                   „              (maleinoid)     . 

CgH14O4 

129° 

„ 

asymm.             „                   .... 

CgH14O4 

86° 

„ 

oa-Dimethyl-a-ethylsuccinic 

CgHjA 

139°-140° 

„ 

Tetramethylsuccinic                                ; 

CgH14O4 

•Mf 

147° 

Isoamylsuccinic         ..... 

CgHjA 

75°-76° 

— 

n-Hexylsuccinic         ..... 

C10H18O4 

87° 

57° 

symm.  Dipropylsuccinic  (fumaroid)    . 

C10H1804 

182°-183° 

Liquid 

„                    „              (maleinoid)  . 

C10H1804 

119°-12r 

H 

n-Heptylsuccinic       ..... 

CU^^A 

90°-91° 



symrn.  Difsobutylsuccinic  (fumaroid) 

C12H22O4 

195° 

Liquid 

„                     „                (maleinoid) 

CjaHgA 

97°-98° 

„ 

Tetraethylsuccinic     ..... 

C12H22O4 

149° 

86° 

Tetrapropylsuccinic            .          .          .         . 

C'l6H30°4 

137° 

— 

Pure  succinic  acid  crystallises  in  monoclinic  plates,  m.-pt.  182°,  b.-pt.  235°,  having 
a  disagreeable  acid  taste.  When  subjected  to  distillation,  it  loses  water  and  yields  succinic 
anhydride.  Its  solubility  in  water  is  1  :  20  at  the  ordinary  temperature,  and  it  is  highly 
resistant  to  the  action  of  oxidising  agents. 

Calcium  succinate  is  soluble  in  water ;  ferric  succinale  is  used  in  the  estimation  of  iron. 

(6)  ISOSUCCINIC     ACID      (Ethylidenesuccinic      or    Methylpropandioic     Acid^, 

CO  H 
CH3  •  CH<^p_.2TT,  forms  needles  or  prisms  which  melt  at  130:  with  evolution  of  CO2  and 

formation  of  propionic  acid.  It  is  more  soluble  in  water  than  its  isomeride,  but  yields 
no  anhydride.  It  is  obtained  by  synthesis  from  ethyl  malonate,  or  by  treatment  of 
a-bromopropionic  acid  with  KCX  and  subsequent  hydrolysis. 


2Na  •  CH<2  +  CH2I2  =  2NaI  +  CH2 


CH2  =  2C02 


372  ORGANIC    CHEMISTRY 

PYROTARTARIC  ACIDS,   C5H8O4  (Four  Isomerides) 

(a)  GLUTARIC     ACID      (Normal      Pyrotartaric     or     Pentadioic     Acid), 
C02H  •  CH2  •  CH2  •  CH2  •  CO2H,  forms  crystals  melting  at  97'5°  and  is  readily 
soluble  in  water.      It  is  obtained  from  1  mol.  of  methylene  iodide  and  2  mols. 
of  ethyl  sodiomalonate,  the  intermediate  product  being  hydrolysed  and  2  mols. 
of  C02  then  eliminated  by  heating  : 

/-m  ^      „      _    . 
C02  *  C2H5 

j '  C2H5 
c*c\   •  r*  TI 

<^2     ^2n5 

CH2  •  C02H 
CH2 

P*TT     •  C*f\  TI 
v^-tL2      Uwtjil 

Glutaric  acid 

p 

(b)  PYROTARTARIC  ACID  (Methylbutandioic  Acid), 

C02H  •  CH2  •  CH  •  CO2H 

CH3 

is  formed,  together  with  pyruvic  acid,  when  ordinary  tartaric  acid  is  subjected 
to  dry  distillation;  synthetically  it  is  prepared  from  ethyl  acetoacetate.  It 
forms  small  tri clinic  crystals  melting  at  117°  and  its  anhydride  is  known. 
Since  it  contains  an  asymmetric  carbon  atom,  it  exists  in  two  optically  active 
stereoisomerides . 

HIGHER  HOMOLOGUES 

The  dialkylsuccinic  acids  (see  above)  contain  two  asymmetric  carbon  atoms 
and  give  rise  to  important  cases  of  stereoisomerism.  Together  with  the  horno- 
logues  of  glutaric  and  adipic  acids,  they  are  found  among  the  products  of  decom- 
position of  the  terpenes  and  hence  serve  to  establish  the  composition  of  these. 

/3-METHYLADIPIC  ACID,  C02H  •  CH2  •  CH(CH3)  •  CH2  •  CH2  •  C02H,  melts 
at  85°  and  occurs  along  with  menthol,  etc.,  in  the  oxidation  products  of 
numerous  ethereal  oils. 

SUBERIC  ACID  (Octandioic  Acid),  C02H  •  [CH2]6  •  C02H,  is  obtained  by  boiling 
cork  waste  or  fatty  oils  with  nitric  acid ;  it  melts  at  141°  and  its  anhydride  at  62°,  while 
its  ethyl  ester  boils  at  281°.  Distillation  of  the  calcium  salt  yields  suberone  (ketoheptamethy- 
lene). 

AZELAIC  ACID,  C02H  •  [CH2]7  •  CO2H,is  now  obtained  easily  and  cheaply  by  decom- 
posing the  ozonides  of  oils  and  of  the  corresponding  unsaturated  fatty  acids,  especially 
of  oleic  acid  (E.  Molinari,  Soncini,  and  Fenaroli,  1906-1908).  The  acid  oiiginally  cost 
£24  per  kilo,  but  can  now  be  sold  for  a  few  shillings.  -It  is  obtained  well  crystallised  from 
benzene  or  from  water,  in  which  it  dissolves  easily  in  the  hot  but  only  slightly  in. the  cold 
(1-648  per  cent,  at  55°,  "0-817  per  cent,  at  44-5°,  0-214  per  cent,  at  22°,  and  0-212  per  cent, 
at  15°);  it  is  soluble  also  in  alcohol  or  ether,  melts  at  106°,  and  gives  a  calcium  salt  which 
dissolves  in  cold  but  not  in  hot  water. 

SEBACIC  ACID  (Decandioic  Acid),  CO2H  •  [CH2]8  •  CO2H,  melts  at  133°  and  is  formed 
when  oleic  acid  is  dry-distilled  or  when  stearic  or  ricinoleic  acid  is  oxidised  with  nitric 
acid.  Its  anhydride  melts  at  78°  and  its  diethyl  ester  boils  at  196°. 

Sebacic  acid  is  now  used  industrially  for  the  separation  of  thorium  from  the  rare  earths 
(see  Vol.  I.,  p.  505). 


OLEFINEDICARBOXYLIC    ACIDS  373 

HIGHER   HOMOLOGUES  OF   OLEFINEDICARBOXYLIC   ACIDS 


Name  of  Acid 

Structure 

Melting-point 
of  acid 

Melting-point 
of  the 
anhydride 

Boiling-point 
of  the 
anhydride 

Dimethylfumaric      (a-methyl- 

mesaconic) 

CH,  •  CX  :  CX  •  OH, 

239°-240° 

— 

— 

Ethylfumaric    (y-methylmesa 

conic) 

CH,  •  OH,  •  OX  :  CHX 

194°-196° 

— 

— 

Ethylmaleic      (y-methylcitra 

conic) 

CH,  •  CH,  •  OX  :  CHX 

100° 

Liquid 

229° 

a-Methylitaconic    . 

CH,  :  OX  •  OHX  •  CH, 

150°-1518 

62°-63° 

.  —  . 

y-Methylitaconic    . 

OH,  •  OH  :  CX  •  CH,X 

166°-167° 

— 

— 

Propylfumaric 

CH,  •  CH2  •  CH,  •  CX  :  CHX 

174°-175° 

— 

.  —  . 

Propylmaleic 

OH,  •  CH,  •  CH,  •  CX  :  CHX 

93°-95° 

— 

243°-245° 

y-Ethylitaconic 

CH,  •  OH,  •  OH  :  CX  •  OH2X 

162°-167° 

— 

— 

Allylsuccinic 
Isopropylfumaric  . 

CH,  :  CH  •  CH,  •  CHX  •  CH,X 
(CH8),OH  •  CX  :  OHX 

92°-93° 
185°-186° 

Liquid 

About  20° 

Isopropylmaleic     . 

(CH8)2CH  •  CX  :  CHX 

91°-93° 

+  5° 

138°  (61  mm  ) 

yy-Dimethylitaconic  (te  aconi  ) 

/pTT   \  r~i  .  p"V"  .  pTT  "Y" 

160°—  161° 

44° 

197°  (22  mm.) 

y-Methylene-y-methylpj  ro- 

tartaric 

CH,  :  C(CH3)  •  OHX  •  CH,X 

146°-147° 

Liquid 

-  —  . 

Methylethylmaleic 

CH,  •  CH,  •  OX  :  CX  •  CH, 

— 

,, 

230° 

a-Ethylitaconic 

OH,  :  CX  •  CHX  •  CH2  •  CH, 

150° 

52° 

— 

ay-Dimethylitaconic 

OH,  •  CH  :  CX  •  CHX  •  CH, 

202° 

Liquid 

131°  (16  mm.) 

aa-Dimethylitaconic 

OH,  :  OX  •  OX(CH,), 

142-5° 

210°-215° 

Butylfumaric 

0,H6  •  CH,  •  CH,  •  CX  :  CHX 

170° 

— 

— 

Butylmaleic  . 

02HS  •  CH,  •  CH.  •  CX  :  OHX 

80° 

.  —  • 

— 

y-Propylitaconic    . 

CjHs  •  CH2  •  CH  :  CX  •  CH2X 

159°-160° 

.  —  . 

Isobutylfumaric     . 

(CH,)2CH  •  OH,  •  CX  :  CHX 

183° 

— 

— 

Isobutylmaleic 

(CH3)2CH  •  CH2  •  OX  :  OHX 

78°-81° 

— 

— 

y-Isopropylitaconic 

(OH8\CH  •  OH  :  OX  •  CH,X 

189°-192° 

.  —  . 

— 

Methylpropylmaleic 
Methylisopropylmaleic 

CH,  •  OH,  •  OH,  •  OX  :  OX  •  CH. 
(CH,),CH  •  CX  :  OX  •  CH, 

— 

Liquid 

241°-242° 
240°-242° 

Diethylmaleic 
y-Methyl-a-ethylitaconic 

0,H,  •  OX  :  CX  •  02H6 
CH,  •  CH  :  CX  •  OHX  •  02H6 

136° 

" 

239°-240° 
143°  (12  mm.) 

CHO      Fumaric  acid 


444 


B.  UNSATURATED   DIBASIC   ACIDS 

I.  OLEFINEDICARBOXYLIC   ACIDS,   CnH2n_4O4 

C02H-CH 


CH  •  CO..H 


C6H804 


CCHCO 


Maleic  acid 
Mesaconic  acid 
Citraconic  acid 
Itaconic  acid 


Glutaconic  acid    . 
Pyrocinchonic  acid 


HC  •  C02H 


HC  •  C02H 
C02H  •  C  •  CH3 


CH  •  CO2H 
CH,  •  C  •  CO,H 


x    .  CH-C02H 

CH2  :  C  •  C02H 

CH2  •  CO2H 

C02H  •  CH  :  CH  •  CH2  •  CO2H 
CH3  •  C  •  C02H 


melts  at  200°  (sublimes) 
„       130°  boils  at  160° 
„       202° 
„         91° 
„       161° 

132°          — 


CH3  •  C  •  C02H 


Pyrocinchonic  an- 
hydride 


CH,  •  C— CO 


o 


CH,  •  C— CO' 


C6H8O4  a/3-Hydromucic  acid  CO2H  •  CH2  •  CH2  •  CH  :  CH  •  C02H 


96°  boils  at  223° 

169°  (stable) 
C02H  •  CH2  •  CH  :  CH  •  CH2  •  CO2H      „      195°  (labile) 

As  far  as  the  carboxyl  groups  are  concerned,  these  acids  have  chemical 
properties  similar  to  those  of  the  saturated  dibasic  acids  (see  p.  364),  whilst, 
as  they  are  unsaturated  compounds,  they  are  able  to  combine  with  2  atoms 
of  hydrogen  or  halogen  or  with  1  mol.  of  a  halogen  hydracid. 


374  •     ORGANIC    CHEMISTRY 

They  are  usually  prepared  from  the  mono-  and  di-halogen  substitution 
products  of  succinic  acid  and  its  homologues  by  removing  either  1  mol.  of 
halogen  hydracid  (by  heating  with  KOH)  or  2  atoms  of  halogen  : 

CH2  •  CO2H  HBr  +  CO2H  •  CH 

I  -  II 

CHBr  •  C02H  CH  •  C02H 

Monobromosuccinic  acid  Fumaric  acid 

Distillation  of  the  saturated  dibasic  hydroxy-acids  results  in  the  removal 
of  1  mol.  of  H2O  and  the  formation  of  unsaturated  acids. 

The  most  interesting  cases  of  stereoisomerism  were  considered  on  p.  21. 
When  fumaric  acid  is  either  heated  or  treated  with  PC15,  POC13,  or  P2O5,  it 
is  converted  into  maleic  anhydride.  Maleic  acid  is  transformed  into  fumaric 
acid  by  heating  at  200°  in  a  sealed  tube  or  by  the  action  of  bromine  or  of  various 
acids  in  presence  of  sunlight. 

FUMARIC    ACID    (trans-Butendioic    Acid),    C4H404    or    C02H  •  CH, 

II 

HC  •  CO2H 

forms  small  white  prisms  which  have  a  marked  acid  taste  and  are  almost 
insoluble  in  water;  it  does  not  melt,  but  sublimes  at  about  200°,  subsequently 
losing  water  and  becoming  converted  largely  into  maleic  anhydride. 

It  is  moderately  widespread  in  certain  vegetable  organisms,  e.  g.,  in  fungi, 
truffles,  Iceland  moss,  and  especially  in  Fumaria  officinalis.  It  may  be  pre- 
pared by  the  ordinary  synthetical  methods  and  also  by  the  action  of  phosphorus 
and  bromine  on  succinic  acid,  the  product  obtained  being  decomposed  by 
heating  with  water. 

It  is  stereoisomeric  with  maleic  acid  (see  p.  22)  and  its  reduction  to  normal 
succinic  acid  by  means  of  nascent  hydrogen  confirms  its  constitution,  which 
is  also  deduced  from  the  decomposition  of  the  corresponding  ozonide  (Harries). 

The  Silver  Salt,  C4H2O4Ag2,  is  slightly  soluble  in  water,  and  the  same  is  the 
case  with  the  barium  salt,  C4H204  Ba  +  3H2O,  which  in  boiling  water  becomes 
insoluble  and  separates  in  the  anhydrous  form,  C4H2O4Ba. 

MALEIC  ACID  (cis-Butendioic  Acid),  C4H4O4  or   CH  •  CO2H,  forms  large 

CH  •  C02H 

prisms  melting  at  130°  and  having  an  unpleasant  taste ;  it  boils  at  160°,  losing 
water  and  becoming  converted  partially  into  maleic  anhydride.  It  is  readily 
soluble  in  water.  .  • 

Its  ready  transformation  into  maleic  anhydride  is  explained  by  the  stereo- 
chemical  relations  considered  on  pp.  21  et  seq.,  and  in  many  general  methods 
of  preparing  the  acid,  the  anhydride  is  first  obtained. 

The  Barium  Salt,  C4H204Ba  +  H2O,  is  soluble  in  hot  water,  from  which 
it  crystallises  well. 

Electrolysis  of  the  alkali  salts  of  fumaric  and  maleic  acids  yields  acetylene. 
When  heated  with  sodium  hydroxide  at  100°,  these  two  acids  are  converted 
into  inactive  malic  acid. 

ITACONIC  ACID  (Methylenesuccinic  Acid),  C5H6O4  or  CH2  :  C  •  C02H,  is  a  white 

CH2  •  C02H 

substance  melting  at  161°  and  non-volatile  in  steam.  It  is  obtained  by  the  action  of 
water  on  its  anhydride,  the  latter  being  formed  by  the  interaction  of  citraconic  anhydride 
and  water  at  150°.  Hydrogen  converts  it  into  pyrotartaric  acid  and  permanganate  into 
hydroxyparaconic  acid.  On  electrolysis  it  yields  allene,  CH2 :  C :  CH2. 

MESACONIC  ACID  (Methylfumaric  Acid),  C5H6O4  or  CO2H  •  C  •  CH3,  is  formed  by 

II 

HC  •  CO,H 


GLUTACONICACID  375 

heating  citraconic  or  itaconic  acid  with  water  at  200°  or  by  treatment  of  citraconic  acid 
with  dilute  HNO3  or  concentrated  NaOH,  or  with  traces  of  bromine  in  sunlight.  It  is 
difficultly  soluble  in  water,  melts  at  202°,  and  does  not  distil  in  steam.  When  electrolysed 
it  forms  allylene,  CH3  •  C  |  CH,  while  with  hydrogen  it  gives  pyrotartaric  acid  and  with 
permanganate,  pyrotartaric  and  oxalic  acids.  It  forms  a  barium  salt,  C5H4O4Ba  +  4H  O. 
CITRACONIC  ACID  (Methylmaleic  Acid),  C5H604  or  CH3  •  C  •  CO2H,  is  formed  from 

II 
HC  •  CO2H 

the  corresponding  anhydride  and  water.  It  melts  at  91°,  differs  from  the  two  preceding 
acids  by  being  very  soluble  in  water,  distils  in  steam  and  readily  gives  the  anhydride 
again.  On  electrolysis  it  yields  allylene,  while  with  hydrogen  it  forms  pyrotartaric  acid. 

GLUTACONIC  ACID,  C5H6O4  or  C02H  •  CH  :  CH  •  CH2  •  CO2H,  is  isomeric  with  the 
three  preceding  acids,  and  is  obtained  by  hydrolysing  the  corresponding  ester  with  HC1  ; 
it  melts  at  132°  and  the  hydrogen  of  its  CH2-  group  is  replaceable  by  sodium  (see  p.  368). 

Of  the  higher  homologues  of  these  acids  mention  may  be  made  of  the  alkylitaconic 
acids,  with  which,  on  heating  with  NaOH  solution,  the  position  of  the  double  linking 
changes,  gives  alkylmesaconic  and  alkylaticonic  acids  (Fittig),  e.  g.,  isobutylaticonic  acid, 
(CH3)2CH  •  CH  :  CH  •  CH(C02H)  •  CH2  •  C02H,  which  melts  at  93°  ;  with  alkalis  these 
acids  undergo  the  reverse  change  to  some  extent. 

The  calcium  and  barium  salts  of  the  alkylmesaconic  acids  are  readily  soluble  in  water, 
and  those  of  the  alkylitaconic  acids  slightly  soluble. 

Of  these  homologous  acids,  the  following  deserve  mention  : 

PYROCINCHONIC  ACID  (Dimethylmaleic  or  Dimethylfumaric  Acid),  C6H8O4  or 
CO2H  •  C  =  C  •  CO2H.  Of  the  two  stereoisomerides,  only  dimethylmaleic  acid  was  until 

CH3  CH3 

recently  known,  and  then  only  as  the  anhydride,  namely,  pyrocinchonic  anhydride  (m.-pt. 
96°,  bi-pt.  223°).     Dimethylmaleic  acid  cannot  exist  in  the  free  state,  as  it  immediately 
gives  up  water,  forming  the  anhydride  ;  its  esters  are,  however,  known. 
CH3  •  C  •  COv 

The  anhydride,  M),  may  be  prepared  in  various  ways,  e.  g.,  by  distilling  in 

CH3  •  C  •  CO/ 

steam  the  product  of  the  interaction  of  pyrotartaric  acid  and  sodium  succinate,  but  a 
better  yield  is  obtained  by  first  preparing  the  nitrile  of  methylacetoacetic  acid  and  distilling 
this  in  a  vacuum. 

According  to  A.  Bischoff,  the  stereoisomeride,  Dimethylfumaric  Acid,  CH3  •  C  •  C02H. 

C02H  •  C  •  CH3 

could  not,  owing  to  stereochemical  considerations,  be  formed  in  the  free  state,  but  Fittig 
and  Kettner  (1899)  and  also  E.  Molinari  (1900)  have  succeeded  in  isolating  it  in  various 
ways.1  It  forms  white  crystals,  m.-pt.  152°  ;  its  amido-derivatives  have  also  been  prepared. 
Bauer  (1904)  made  the  interesting  observation  that  dimethylfumaric  acid  and,  in 
general,  compounds  containing  carboxyl  or  alkyl  or  phenyl  groups  or  bromine  atoms 
united  to  two  carbon  atoms  connected  by  a  double  linking,  do  not  unite  with  bromine. 


1  Fittig  and  Kettner,  making  use  of  the  property  of  various  acids,  homologous  with  citraconic 
acid,  of.  yielding  the  corresponding  fumaroid  isomeride  when  simply  heated  with  alkali,  obtained  from 
yrocinchonic  anhydride  the  two  acids  :  one  melting  at  151°,  to  which  is  ascribed  the  constitution 
Ha  :  G  •  C02H  (&-methylitaconic  acid),  and  another  melting  at  240°  and  regarded  as  CH3  •  C  •  C02H 


p 
C 


• 
CH;  •  CH  •  C02H  C02H  •  C  •  CH3 

(dimethylfumaric  acid).     It  is  highly  probable,  for  the  following  reasons,  that  the  latter  constitu- 
tion should  be  attributed  to  the  acid  melting  at  151°  : 

By  a  long  series  of  investigations  (1881  to  1896),  Korner  and  Menozzi  showed  that,  in  general, 
the  treatment  of  a-amino*acids  with  methyl  iodide  in  presence  of  caustic  potash  yields  the  corresponding 
betaines  (condensed  alkyl-substituted  amines),  but  the  fi-amino-acids,  if  similarly  treated,  always 
yield  the  corresponding  unsaturated,  non-nitrogenous  acids  of  the  fumaroid  type  (betaines  being 
probably  formed  as  intermediate  products).  As  the  same  &-amino-acid  can  be  obtained  from  the 
two  stereoisomeric  unsaturated  acids,  this  general  reaction  renders  it  possible  to  pass  from  a  maleinoid 
unsaturated  acid  to  the  corresponding  fumaroid  stereoisomeride.  By  applying  this  reaction  to 
pyrocinchonic  anhydride,  E.  Molinari  arrived  at  the  expected  stereoisomeride  (dimethylfumaric 
acid),  melting  at  152°. 


376  ORGANIC    CHEMISTRY 

HYDROMUCONIC  ACIDS,  C6HgO4.  Of  these  are  known  ( 1 )  the  a^-unsaturated  acid, 
C02H  •  CH2  •  CH2  •  CH  :  CH  •  CO2H,  which  is  stable  and  melts  at  169° ;  with  permanganate 

S  y  ft  a 

it  yields  succinic  acid.  (2)  The  unstable  £y-acid,  C02H  •  CH2  •  CH  :  CH  •  CH2  •  C02H, 
which  melts  at  195°  and  is  obtained  by  reducing  muconic  acid;  when  heated  with  alkali, 
it  is  converted  into  the  stable  isomeride,  whilst  with  permanganate  it  gives  malonic  acid, 
C02H  •  CH2  •  C02H. 

Of  the  DIOLEFINEDICARBOXYLIC  ACIDS,  only  Muconic  Acid,  CO2H  •  CH  . 
CH  •  CH  :  CH  •  CO2H,  melting  above  260°,  need  be  referred  to. 

Of  the  ACETYLENEDICARBOXYLIC  ACIDS,  mention  will  be  made  only  of 
Acetylenedicarboxylic  (Butindioic)  Acid,  C02H  •  C  •  C  •  C02H,  which  melts  and 
decomposes  at  175°;  it  crystallises  with  2H2O.  It  is  obtained  on  removing  HBr  from 
dibromo-  or  isodibromo-succinic  acid  by  means  of  potash. 

Diacetylenedicarboxylic  Acid,  CO2H  •  C  :  C  •  C  :  C  •  CO2H  +  H2O,  turns  dark  red  in 
the  light  and  explodes  at  177°.  When  reduced  with  sodium  amalgam,  it  yields  hydro- 
muconic  acid. 

Tetracetylenedicarboxylic  Acid,  CO2H  -C:C-C:C-CiC-C:C-  C02H,  forms 
white  crystals  which  blacken  rapidly  in  the  light  and  explode  violently  on  heating. 

C.  TRIBASIC   ACIDS 

These  have  usually  been  obtained  synthetically,  and  are  not  very  stable, 
since  they  readily  yield  carbon  dioxide  and  dibasic  acids  when  heated ;  their 
esters,  however,  exhibit  increased  stability.  Their  properties  and  methods  of 
preparation  vary  according  as  the  carboxyl  groups  are  united  to  one  or  to 
various  carbon  atoms. 

Of  the  many  such  acids  known,  the  following  may  be  mentioned  : 

TRICARBALLYLIC  ACID  (symm.  wato'-Propanetricarboxylic  or  Pentanedioic-3- 
methyloic  Acid)  CH2  .  CO2H,  occurs  in  the  deposits  left  on  concentrating  beet-sugar  juices 

CH  •  CO2H 

CH2  •  C02H 

in  vacuo.  Synthetically  it  is  obtained  by  converting  glycerol  into  the  tribromohydrin 
or  allyl  tribromide,  which  is  treated  with  potassium  cyanide  to  give  the  corresponding 
tricyano-compound,  the  latter  being  then  hydrolysed  to  tricarballylic  acid;  the  con- 
stitution of  the  acid  is  thus  proved.  This  acid  forms  white,  prismatic  crystals  melting 
at  166°.  It  may  also  be  prepared  by  reducing  unsaturated  tricar boxylic  acids  (e.  g.,  aconitic 
acid ). 

C02H  C02H  C02H 

CAMPHORONIC  ACID  (aa^-Trimethylcarballylic  Acid),  CH3  •  C C CH2 

CH3     CH3 

is  formed  on  oxidising  camphor,  of  which  it  serves  to  indicate  the  constitution ;  it  melts 
at  135°. 

ACONITIC  ACID  is  an  unsaturated  tribasic  acid  of  the  constitution  CO2H  •  CH2  • 
C(C02H) :  CH  •  C02H,  and  is  found  in  beetroot,  sugar-cane,  Aconitum  napellus,  etc.  It  is 
obtained  synthetically  by  eliminating  C02  from  citric  acid  by  the  action  of  heat  or  of 
various  reagents.  It  melts  at  191°,  losing  CO2,  and  forming  itaconic  anhydride.  It 
dissolves  readily  in  water  and  with  nascent  hydrogen  generates  tricarballylic  acid,  its 
structure  being  indicated  by  this  reaction. 

D.  TETRABASIC   ACIDS 

These  are  formed  from  ethyl  sodiomalonate  (see  p.  368)  by  means  of  an  unsaturated 
ester,  e.  g.,  of  fumaric  acid.  When  heated,  they  lose  C02,  forming  tribasic  and,  better, 
dibasic  acids. 

Olefinetetracarboxylic  Acids  are  also  known. 


HALOGENATED    ACIDS  377 

FF.    DERIVATIVES    OF   THE   ACIDS 
I.  HALOGEN   DERIVATIVES 

One  or  more  of  the  hydrogen  atoms  of  an  alkyl  group  united  with  carboxyl 
may  be  replaced  by  halogens,  the  carboxyl  group  being  left  intact.  The 
halogen  derivatives  of  the  acids,  thus  obtained,  are  more  markedly  acid  in  character 
than  the  original  substances.  They  are  obtained  by  the  action  of  chlorine  or 
bromine  in  sunlight  or,  better,  by  heating  the  acid  with  the  halogen  in  presence 
of  a  little  water  or  sulphur. 

On  the  other  hand,  the  hydroxyl  of  the  carboxyl  group  may  be  replaced, 
forming  acid  halides  :  —  CO  —  X  (by  treating  the  acid  with  phosphorus  chloride 
or  bromide).  That  the  halogen  has  replaced  the  hydroxyl  group  is  shown 
by  the  fact  that  these  acid  halides  yield  the  original  acids  when  treated  with 
cold  water,  whilst  halogens  are  not  displaced  from  alkyl  residues  in  this  way. 
These  acid  chlorides  and  bromides  readily  give  the  monochloro-  and  mono- 
bromo-  acids  when  treated  further  with  chlorine  or  bromine. 

(a)  HALOGENATED   ACIDS 

When  the  carbon  atom  (a),  to  which  the  carboxyl  group  is  attached,  is 
not  united  directly  with  hydrogen  [e.  g.,  in  trimethylacetic  acid,  (CH3)3C  •  C02H], 
bromine  is  not  taken  up  (see  p.  375).  The  constitution  of  a  halogenated  acid, 
or  rather  the  position  of  the  halogen  atom,  is  deduced  from  that  of  the  corre- 
sponding hydrpxy-acid  (containing  a  hydroxyl  group  in  place  of  the  halogen) 
obtained  by  heating  the  halogenated  acid  with  sodium  carbonate  solution  or 
with  water  and  lead  oxide. 

On  the  other  hand,  the  passage  from  hydroxy-acid  to  the  corresponding 
halogenated  acid  may  be  effected  by  treatment  with  phosphorus  chloride  or 
bromide. 

The  acid  character  becomes  more  marked  on  passing  from  the  iodo-  to  the 
bromo-  and  then  to  the  chloro-compounds,  and  also  increases  with  the  number 
of'halogen  atoms  in  the  molecule. 

While  the  a-halogenated  acids  readily  yield  the  corresponding  hydroxy- 
acids,  the  /S-acids  yield  the  corresponding  unsaturated  acids  (see  p.  352)  and 
may  even  lose  C02,  giving  unsaturated  hydrocarbons,  but  the  y-halogenated 
acids,  when  heated  with  sodium  carbonate  solution  or  with  water  alone,  give 
up  a  molecule  of  halogen  hydracid  and  yield,  not  the  unsaturated  acids,  but 
lactones  (see  p.  355). 

When  halogenated  acids  are  prepared  by  the  interaction  of  an  unsaturated 
acid  with  a  halogen  hydracid  (e.  g.,  HI),  the  halogen  becomes  attached  to  the 
least  hydrogenated  carbon  atom  (see  p.  116).  Thus,  with  a  zl^-acid,  where 
the  double  linking  is  between  the  a-  and  /3-carbon  atoms,  the  halogen  unites 
with  the  latter. 

The  halogenated  and  poly-halogenated  acids  exhibit  isomerism,  since  the 
halogen  atom  may  be  joined  to  the  a,  /3,  y,  etc.,  carbon  atom,  or  several  halogen 
atoms  may  be  united  with  one  and  the  same  carbon  atom  or  with  different  ones. 

When  heated  with  potassium  cyanide,  the  mono-haloid  acids  yield  cyano- 
acids : 

CH2C1  •  COOK  -f  KCN  =  KCL+  CN  •  CH2  •  COOK. 

Potassium  chloroacetate  Potassium  cyanoacetate 

With  sodium  sulphite  they  give  dibasic  sulpho-acids,  the  sulphonic  group 
of  which  is  readily  replaced  by  hydroxyl  by  boiling  with  alkali  : 

Na2S03  +  Cl  •  CH2  •  COONa  =  NaCl  +  S03Na  •  CH2  •  COONa 

Sodium  sulphoacetate 

With  reference  to  the  affinities  of  the  halogenated  acids,  see  Note  on  p.  323. 


378 


ORGANIC    CHEMISTRY 


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ACIDHALIDES  379 

MONOCHLORACETIC  ACID  (Chlorethanoic  Acid),  CH2C1  •  COOH,  is  prepared  by 
the  general  method,  that  is,  by  passing  dry  chlorine  into  hot  acetic  acid  in  presence  of 
acetic  anhydride,  phosphorus,  or  sulphur  (with  1  per  cent,  of  sulphur,  an  80  per  cent,  yield 
is  obtained).  It  forms  rhombic  crystals  which  corrode  the  flesh  and  melt  at  62°;  on 
solidification  an  unstable  modification  is  obtained  which,  for  some  time,  melts  at  52°; 
it  boils  at  186°.  When  heated  with  water  or  alkali  it  gives  Hydroxyacetic  Acid  (glycollic 
acid),  OH  •  CH2  •  CO2H;  with  ammonia  it  yields  Aminoacetic  Acid  (glycine  or  glycocoll), 
NH2  •  CH2  •  C00H. 

&  &  £t 

The  properties  of  the  other  halogenated  acids  are  given  in  the  Table  on 
the  preceding  page. 

(b)  ACID   HALIDES 

Of  these  compounds  the  most  important  are  the  chlorides  of  the  acid  radicals, 
which  are  termed  acichlorides  or  chloranhydrides.  Although  acetyl  chloride, 
CH3  •  CO  '  Cl,  is  readily  obtainable,  it  has  not  been  found  possible  to  prepare 
formyl  chloride,  H  •  CO  •  Cl,  a  mixture  of  CO  +  HC1  being  always  obtained. 

These  compounds  are  usually  colourless  liquids,  which  have  pungent  odours 
and  fume  strongly  in  the  air,  the  moisture  in  the  latter  liberating  hydrogen 
chloride.  Their  boiling-points  are  below  those  of  the  corresponding  acids,  and 
they  distil  without  decomposing;  the  higher  members  are,  however,  solid 
and  do  not  distil  unchanged  even  in  a  vacuum. 

The  principal  methods  for  preparing  these  substances  are  as  follows  : 

(a)  The  organic  acid  is  heated  for  a  short  time  on  the  water-bath  with 
PC15  (with  higher  acids),  PC13  (with  acids  below  C 10)  or,  in  some  cases,  sulphuryl 
chloride,  S02C12 : 

CnH23  •  CO  •  OH  +  PC15  =  CUH23  •  CO  •  Cl  +  HC1  +  POC13, 

Laurie  acid 

the  phosphorus  oxychloride  and  hydrochloric  acid  being  eliminated  by  dis- 
tillation in  vacuo ;   or, 

3CH3  •  CO  •  OH  +  2PC13  =  3CH3  •  CO  •  Cl  -f  3HC1  +  P203, 

the  acetyl  chloride  thus  formed  being  separated  by  distillation,  .while  the  P203 
is  left  in  the  residue. 

(b)  With  thionyl  chloride  the  acids  yield  the  chloranhydrides,  the  other 
products  formed  at  the  same  time  being  volatile  and  hence  easily  removable  : 
X  •  CO  •  OH  +  SOC12  =  X  •  CO  •  Cl  +  HC1  +  SO2. 

(c)  In  some  cases  the  acid  is  treated  simply  with  HC1  in  presence  of  a 
dehydrating  agent,  (P205)  :    CH3  •  CO  •  OH  +  HC1  =  H20  +  CH3  •  CO  •  Cl. 

CHEMICAL  PROPERTIES.  The  great  reactivity  of  the  chlorine  atom 
of  these  substances  renders  them  of  considerable  importance  in  chemical 
syntheses.  Water,  ammonia  (amines),  and  alcohols  decompose  them  in  the 
cold  with  great  violence  : 

CH3 ••  CO  •  Cl  +  H2O  =  HC1  +  CH3  •  CO  •  OH 
CH3  •  CO  •  Cl  +  NH3  =  HC1  +  CH3  •  CO  •  NH2  (acetamide) 
CH3  •  CO  •  Cl  +  C2H5  •  OH  =  HC1  +  CH3  •  CO  •  OC2H5  (ethyl  acetate). 

With  organic  salts  they  yield  anhydrides  : 

CH3  •  CO  •  Cl  +  CH3  •  CO  •  ONa  =  NaCl  -f  CH3  •  CO  •  O  •  CO  •  CH3. 
Sodium  amalgam  reduces  them  to  aldehydes  and  then  to  alcohols. 

ACETYL  CHLORIDE  (Ethanoyl  Chloride),  CH3  •  CO  •  Cl,  is  a  liquid  boiling  at  51° 
and  having  the  sp.  gr.  1-105  at  20°.  It  is  prepared  by  mixing  5  parts  of  glacial  acetic 
acid  and  4  parts  of  phosphorus  trichloride  in  the  cold,  heating  for  a  short  time  at  40°  and, 


380  ORGANIC    CHEMISTRY 

after  evolution  of  HC1  ceases,  distilling  the  acetyl  chloride  and  purifying  it  by  rectification. 
Water  decomposes  it  with  development  of  heat. 

It  is  employed  in  organic  synthesis,  since  it  readily  yields  acetyl  derivatives  of  alcohols 
and  of  primary  and  secondary  amines. 

The  commercial  product  costs  3s.  to  4s.  per  kilo,  and  the  chemically  pure  14s. 

The  boiling-points  of  the  higher  homologues  of  acetyl  chloride  rise  with  the  molecular 
weight  and,  with  isomerides,  that  with  the  normal  constitution  has  the  highest  boiling- 
point;  the  specific  gravity  diminishes  as  the  molecular  weight  increases. 

Acetyl  iodide  boils  at  108°,  propionyl  chloride  at  108°  (the  bromide  at  104°  and  the 
iodide  at  127°);  normal  butyryl  chloride  boils  at  101°  (the  bromide  at  128°  and  the  iodide 
at  146°)  and  isobutyryl  chloride  at  92°  (the  bromide  at  116°);  isovaleryl  chloride  boils  at 
114°  (the  bromide  at  143°  and  the  iodide  at  168°)  and  trimethylacetyl  chloride,  (CH3)3C-CO-Cli 
at  105°. 

II.  ANHYDRIDES 

The  anhydrides  of  organic  acids  were  discovered  by  C.  Gerhardt  in  1851 
and  correspond  with  those  of  the  inorganic  acids,  that  is,  they  may  be  regarded 
as  products  of  the  condensation  of  2  mols.  of  acid  with  expulsion  of  1  mol. 
of  water.  Here  also,  the  organic  anhydrides,  when  they  are  at  all  soluble, 
take  up  water  and  regenerate  the  acids.  With  organic  acids,  however,  more 
varied  and  interesting  cases  are  presented,  since  2  mols.  of  different  acids 
may  condense  (mixed  anhydrides),  while  internal  anhydrides  may  be  formed  by 
condensation  between  the  two  carboxyl  groups  of  a  dibasic  acid. 

The  anhydrides  may  be  regarded  also  as  oxides  of  acid  radicals,  e.  g.,  acetic 

/-ITT    .  rir\ 

anhydride,  prr3  .  pry>O,  or  acetyl  oxide,  (CH3  •  C0)20. 

3 

PROPERTIES.  The  first  members  of  the  series  are  liquid,  the  higher  ones 
solid ;  they  generally  dissolve  but  slightly  in  water,  their  transformation  into 
acids  being  very  slow.  They  have  a  neutral  reaction  and  are  soluble  in  ether 
and  often  in  alcohol. 

With  ammonia  and  the  primary  and  secondary  amines,  they  form  amides 
and  ammoniacal  salts  :  (CH3CO)2O  +  2NH3  =  CH3  •  CO  •  NH2  (acetamide) 
+  CH3  •  CO  •  ONH4  (ammonium  acetate). 

When  heated  with  an  alcohol,  they  give  the  corresponding  ester  and 
acid  : 

(CH3CO)20  +  C2H5  •  OH  =  CH3  •  COOC2H5  -f  CH3  •  COOH. 

With  halogen  hydracids  in  the  hot  they  yield  the  halides  of  the  acids  and 
the  free  acids  :  (CH3CO)20  +  HC1  =  CH3  •  CO  •  Cl  +  CH3  •  COOH. 

With  the  halogens  they  give  acid  halides  and  halogenated  acids  :  (CH3CO)2O 
+  C12  =  CH3  •  CO  •  Cl  +  CH2C1  •  C02H. 

Aldehydes  combine  with  anhydrides,  forming  esters,  while  sodium  amalgam 
reduces  anhydrides  to  aldehydes  and  alcohols. 

GENERAL  METHODS  OF  PREPARATION,  (a)  By  the  action  of  acid 
chlorides  on  the  dry  alkali  salts  of  the  corresponding  acids  : 

CH3  •  CO  •  Cl  +  CH3  •  COONa  =  NaCl  +  ®j*  '.  ^Q>O. 

(b)  The  same  result  is  obtained  by  the  action  of  phosphorus  oxychloride 
(or  phosgene,  COC12)  on  a  mixture  of  the  alkali  and  alkaline-earth  salts  of 
the  corresponding  acid,  the  acid  chloride  being  formed  as  an  intermediate 
product. 

(c)  The  higher  anhydrides  are  obtained  from  the  corresponding  acids  by 
the  action  of  acetyl  chloride  : 

CH3  •  COC1  -f  2X  •  COOH  =  HC1  +  CH3  •  COOH  +  (X  •  C0)20. 


ACETIC    ANHYDRIDE 


381 


(d)  The  formation  of  anhydrides  from  the  acids  by  the  subtraction  of 
water  (by  means  of  P205)  gives  low  yields,  the  best  being  obtained  with 
palmitic  and  stearic  acids  (using  acetic  anhydride  in  the  hot  as  dehydrating 
agent). 

The  properties  of  the  best-known  anhydrides  are  given  in  the  following 
Table  : 


Formula 

Name 

Melting- 
point 

Boiling-point 

Specific  gravity 

(CH3  -C0)20 

Acetic  anhydride     . 

.  

136-5° 

1-078  (at  21°) 

(C2H5-CO)20 

Propionic  anhydride 

— 

168-6° 

1-034  (atO°) 

(C3H7-CO)20 

norm.  Butyric  anhydride 

192° 

0-978  (at  12-5°) 

» 

Isobutyric  anhydride 

— 

182° 

0-958  (at  16-5°) 

(C4H9-CO)20 

Isovaleric  anhydride 

— 

215° 

— 

» 

Trimethylacetic  anhydride 

— 

190° 

— 

(C5Hn-CO)20 

norm.  Caproic  anhydride 

242° 

0-928  (at  17°) 

C6H13  -C0)20 

CEnanthic  anhydride 

+  17° 

257° 

0-912  (at  17°) 

(C7H15-CO)20 

Caprylic  anhydride 

-  1° 

186°  (15mm.) 

— 

(C8H17-CO)20 

Pelargonic  anhydride 

+  16° 

207°        „ 

— 

(CuH23-CO)aO 

Laurie  anhydride     .          .1+41° 

166°  (vacuum) 

— 

(C13H27-CO)20 

Myristic  anhydride  .          .      +51° 

198°        „ 

— 

(C15H31-CO)20 

Palmitic  anhydride 

55°-66° 

— 

— 

(C17H35-CO)20 

Stearic  anhydride    .          .         72° 

— 

— 

ACETIC  ANHYDRIDE  (Ethanoic  Anhydride),  (CH3  •  CO)2O,  is  of  importance 
industrially  owing  to  its  use  in  many  organic  syntheses,  as  it  readily  gives  acetyl  derivatives 
with  alcohols  or  with  primary  or  secondary  amines.  It  is  a  suitable  reagent  for  determining 
how  many  hydro xyl  groups  an  organic  substance  contains  (see  Acetyl  Number,  p.  224). 

The  largest  industrial  consumption  of  acetic  anhydride  is  for  making  acetylcellulose 
used  for  non-inflammable  cinematograph  films  and  for  aeroplane  dope ;  its  use  for  artificial 
silk  is  also  anticipated  (see :  Textile  fibres).  Large  quantities  of  the  anhydride  are 
likewise  employed  in  making  organic  dyes,  perfumes  and  drugs. 

It  is  a  colourless,  very  mobile  liquid,  b.-pt.  139-5°,  sp.  gr.  1-078  at  21°  and  1-0876  at 
15°,  index  of  refraction  1-39069  at  15°;  it  has  a  pungent  odour. 

It  dissolves  without  alteration  in  10  parts  of  cold  water  and  is  converted  into  acetic 
acid  only  when  heated,  the  last  portions  only  on  prolonged  boiling.1 

It  is  prepared  by  dropping  5  parts  of  acetyl  chloride  on  to  7  parts  of  dry  powdered 
sodium  acetate,  which  is  kept  cool  meanwhile.  The  mixture  is  subsequently  gently  heated 
for  a  short  time  and  the  anhydride  then  distilled  off  on  a  sand-bath. 

The  commonest  method  of  preparing  it  industrially  appears  to  be  that  utilising  the 

1  Since  commercial  acetic  anhydride  often  contains  considerable  proportions  of  acetic  acid 
(10  to  25  per  cent.),  determination  of  its  strength  by  titration  requires  the  following  precautions  : 
A  weighed  quantity  (about  0-5  gram)  of  the  anhydride  is  introduced  into  a  flask  containing 

N 
100  c.c.  of  clear  baryta  water  of  known  titre  (corresponding,  for  example,  with  94  c.c.  of  lf.  —  HC1), 

the  liquid  being  then  boiled  for  about  half  an  hour  under  a  reflux  condenser  fitted  with  a  soda- 
lime  tube  to  prevent  access  of  C02.  It  is  then  allowed  to  cool  somewhat,  the  excess  of  baryta 
being  rapidly  titrated  with  decinormal  hydrochloric  acid  in  presence  of  a  drop  of  phenolphthalein. 
Another  method  of  hydrolysing  the  acetic  anhydride  consists  in  boiling  it  as  above  for  forty-five 
minutes  with  at  least  100  times  its  weight  of  freshly-boiled  water  (free  from  CO..) ;  the  cold  liquid 
is  then  titrated  with  decinormal  caustic  soda  in  presence  of  phenolphthalein.  The  acidity  is 
calculated  as  though  it  were  all  due  to  acetic  acid,  the  excess  of  the  resulting  percentage  over 
100  being  multiplied  by  5-67  to  give  the  percentage  of  acetic  anhydride  in  the  sample  analysed ; 
subtraction  of  this  number  from  100  gives  the  percentage  of  acetic  acid  present.  Thus,  if  the 
titration  indicates  115-86  per  cent,  of  acetic  acid,  the  percentage  of  acetic  anhydride  will  be 
15-86  X  5-67  =  89-92  and  that  of  acetic  acid,  100  —  89-92  =  10-08. 


sulpl 


Sulphurous  anhydride  present  (rarely)  as  impurity  is  determined  by  means  of  iodine  solution, 
phuric  acid  by  barium  chloride,  and  hydrochloric  acid  by  decinormal  silver  nitrate  solution 


with  potassium  chromate  as  indicator. 


382 


ORGANIC    CHEMISTRY 


reaction  between  sodium  acetate  and  sulphuryl  chloride  l  (see  Vol.  I.,  p.  330),  which,  occurs 

in  two  phases  : 

2CH3  •  C02Na  +  S02C12  =  Na2S04  +  2CH3  •  CO  •  Cl 
CH3  •  CO  •  01  +  CH3  •  C02Na  =  NaCl  +  (C2H30)2O. 

In  practice  rather  more  than  the  theoretical  quantity  of  sodium  acetate  is  used,  and 
all  the  operations  are  carried  out  in  closed  vessels  to  prevent  access  of  moisture  and  loss 
of  sulphuryl  chloride  with  its  unpleasant  odour.  The  sodium  acetate  should  previously- 
be  dried  at  140°  to  reduce  the  moisture  content  to  0-1  per  cent.,  and  the  sulphuryl  chloride 
used  should  distil  to  the  extent  of  92  per  cent,  between  68°  and  69-5°  and  should  have  the 
sp.  gr.  1-675.  Fig.  253  represents  a  scheme  for  an  acetic  anhydride  works  :  The  sodium 
acetate  is  subjected  to  preliminary  heating  in  1  and  is  then  dried  completely  in  three 
vacuum  vessels  below  (2d,  26,  2c),  the  suction  pump  being  at  10.  The  perfectly  dry  salt 
is  distributed  in  several  apparatus  fitted  with  stirrers  on  the  ground-floor  (3a-3gr),  the 
sulphuryl  chloride  being  introduced  from  the  tank  4  and  measured  in  4a-4gr.  In  order 


FIG.  253.     t  . 

that  the  temperature  may  not  rise  much,  the  sulphuryl  chloride  is  fed  gradually  into  each 
vessel,  which  is  fitted  with  a  small  reflux  condensing  column.  When  the  reaction  is 
finished  the  different  apparatus  act  as  stills  and  are  put  into  communication  with  the 
vacuum  pump  10  through  the  collecting  vessels  Qa-Qg  and  the  condensers  for  the  crude  acetic 
anhydride,  5a-5g  ;  7  is  the  general  collecting  tank  for  the  crude  product,  which  contains 
about  90  per  cent,  of  the  anhydride,  the  remainder  being  acetic  acid,  acetyl  chloride, 
sulphur  dioxide  and  other  secondary  products.  The  anhydride  is  purified  by  distillation 
in  a  vacuum  over  anhydrous  sodium  acetate,  followed  by  vacuum  rectification  (by  means 
of  pump  11)  in  a  continuous  column  apparatus,  9-9rf;  0-3-1  per  cent,  of  fuming  nitric  acid 
(U.S.  Pat.  1,069,168,  1913)  or  ozonised  air  may  be  used  in  the  purification. 

1  Of  the  numerous  patents  for  the  industrial  preparation  of  acetic  anhydride,  the  following 
may  be  mentioned  :  treatment  of  sodium  or  calcium  acetate  with  either  sulphuryl  chloride  or 
phosphorus  oxychloricle  and  C02,  or  a  mixture  of  C!  and  SOo  (Ger.  Pats.  161,882,  163,103,  and 
167,304,  1905) ;  treatment  of  sodium  acetate  at  200°  with  silicon  tetrafluoride  (Ger.  Pats.  171,787 
and  171,146,  1906);  Ger.  Pats.  222,236  and  241,898  (Goldschmidt);  Ger.  Pats.  244,602  and 
273,101  (Afga);  Fr.  Pat.  17,674,  1913,  and  Addition  448,342  (Dreyfus);  action  of  S03  +  CC14 
on  sodium  or  calcium  acetate  (U.S.  Pat.  1,113,927,  1914). 


HYDROXY-ACIDS  383 

During  the  European  War  synthetic  acetic  acid  factories  were  erected  in  Great  Britain, 
France  and  Italy  (see  p.  339),  these  making  acetic  anhydride. 

Before  the  war  the  price  of  the  anhydride  in  Germany  was  for  large  parcels  £4-£5  per 
cwt.,  and  for  small  amounts,  up  to  £9;  the  chemically  pure  product  cost  £12. 

The  anhydrides  of  di-  and  poly-basic  acids  are  not  of  great  importance  and  are  con- 
sidered to  some  extent  in  dealing  with  the  corresponding  acids  (succinic,  pyrocinchonic, 
etc.);  with  water  they  yield  the  acids  with  moderate  readiness  (see  pp.  365  and  375). 

III.  HYDROXY-ACIDS 
A.  SATURATED   DIVALENT  MONOBASIC  ACIDS 

These  may  be  regarded  as  derived  from  monobasic  acids  by  the  replacement 
of  an  atom  of  hydrogen  (not  that  of  the  carboxyl  group)  by  a  hydroxyl  group. 
These  acids  possess,  at  the  same  time,  acidic  and  alcoholic  characters  and 
are  hence  termed  divalent  monobasic  acids  or  divalent  alcohol  acids.  The 
hydroxyl  and  the  carboxyl  groups  may  be  substituted  at  the  same  time,  the 
compounds  then  exhibiting  the  general  properties  of  the  acids  and  alcohols, 
in  addition  to  new  and  special  characters  varying  with  the  position  occupied 
by  the  carboxyl  relatively  to  the  hydroxyl  (see  pp.  355  and  357). 

They  are  usually  syrups,  which  may  undergo  crystallisation  ;  in  comparison 
with  the  corresponding  fatty  acids,  the  hydroxy-acids  are  more  soluble  in 
water  and  in  alcohol,  but  less  soluble  in  ether.  They  do  not  distil  unchanged 
and  often  lose  water,  forming  anhydrides. 

GENERAL  METHODS  OF  PREPARATION,  (a)  By  oxidising  dihydric 
alcohols  so  as  to  transform  the  primary  alcoholic  group  into  carboxyl. 

(6)  By  boiling  unsaturated  acids  with  sodium  hydroxide,  so  that  a  molecule 
of  water  is  added  at  the  double  bond. 

(c)  By  substituting  the  halogen  of  a  monohalogenated  monobasic  acid  by 
hydroxyl  ;    this  is  effected  by  treatment  with  KOH  or  with  silver  acetate, 
the  diacetate  formed  in  the  latter  case  being  hydrolysed  by  heating  with 
sodium  carbonate  : 

CH2C1  •  COOH  +  H2O  =  OH  •  CH2  •  C02H  +  HC1. 

Monochloracetic  acid  Glycollic  acid 

(d)  a-Hydroxy-acids  are  obtained  by  hydrolysing  the  nitriles  formed  on 
treating  the  aldehydes  or  ketones  (having  one  atom  of    carbon  less)  with 
hydrocyanic  acid  : 


2H2O  =  NH3  +  CH3  •  CH(OH)  •  COOH. 

Ethylidenecyanohydrin 

Glycolcyanohydrin,  OH  •  CH2  •  CH2  •  ON,  yields  ethylenelactic  acid, 
OH  •  CH2  •  CH2  •  COOH. 

(e)  By  the  action  of  nitrous  acid  on  amino-acids  : 

COOH  •  CH2  •  NH2  +  NO  •  OH  =  H20  +  N2  +  COOH  •  CH2  •  OH. 

Qlycocoll 

(/)  By  reducing  aldehydic  or  ketonic  acids  : 

CH3  •  CO  •  COOH  +  H2  =  CH3  •  CH(OH)  •  COOH. 

Pyruvic  acid  Lactic  acid 

(g)  By  oxidation  of  acids  containing  a  tertiary  carbon  atom,  >  CH  •  COOH, 
with  permanganate. 

PROPERTIES  AND  CONSTITUTION.  The  constitutions  of  these  acids 
can  always  be  deduced  from  the  syntheses  indicated  above.  That  they  con- 
tain an  alcoholic  group  is  shown  by  the  fact  that  the  hydroxylic  hydrogen 
may  be  replaced  by  an  alkyl  group,  giving  true  non-hydrolysable  ethers.  Simi- 
larly the  presence  of  a  carboxyl  group  is  shown  by  the  formation  of  hydrolysable 


384  ORGANIC    CHEMISTRY 

esters.  The  isomerism  exhibited  is  the  same  as  with  the  haloid  derivatives 
of  the  acids. 

The  number  of  alcoholic  hydroxyl  groups  is  determined  by  the  acetyl 
number  (see  p.  224).  The  reactivity,  which  corresponds  with  the  dissociation 
constant,  increases  with  the  proximity  of  the  hydroxyl  to  the  carboxyl  group. 

a-,  /3-,  8-,  and  cZ-hydroxy-acids  are  distinguished  also  by  the  products 
resulting  from  the  elimination  of  one  or  more  molecules  of  water. 

Thus,  a-hydroxy-acids,  when  heated,  lose  2  mols.  of  H2O  per  2  mols. 
of  acid,  the  hydroxyl  group  of  the  one  reacting  with  the  carboxyl  group  of 
the  other  ;  the  compound  formed  is  called  a  lactide  and  is  a  double  ester,  which 
yields  the  acid  again  on  hydrolysis  with  hot  water  or  dilute  acid  : 

CO  -  CH  •  CH3 
COOH  •  CH(OH)  •  CH3  | 

=  2H2O  +  00 

CH3  •  CH(OH)  •  COOH 

CH3-CH-CO 

2  mols.  Lactic  acid  Lactide 

Further,  a-hydroxy-acids,  if  heated  with  sulphuric  acid,  yield  the  aldehydes 
or  ketones  from  which  they  can  originate  (see  above),  formic  acid  being  also 
formed. 

The  /3-acids,  however,  lose  only  1  mol.  of  water,  giving  unsaturated  acids 
(see  p.  352),  while,  when  boiled  with  10  per  cent,  potassium  hydroxide  solution, 
they  give  at  the  same  time  a/3-  and  ay-unsaturated  acids  —  a  reversible  reaction 
leading  to  a  position  of  chemical  equilibrium;  when  heated  with  sulphuric 
acid  they  form  acids  of  the  acrylic  series. 

The  y-  and  8  -acids  lose  1  mol.  of  water,  yielding  lactones  (internal  anhydrides): 

OH  •  CHa  •  CH2  •  CH2  •  COOH  =  H20  +  CH  •  CH  •  CH  •  CO 


y-Hydroxybutyric  acid 


o 


Butyrolactone 

which  are  almost  always  formed  when  attempts  are  made  to  liberate  these 
hydroxy-acids  from  their  salts.  The  lactones  are  neutral  liquids  soluble  in 
water,  alcohol,  and  ether;  they  distil  unchanged  and  with  alkali  form  the 
salts  of  the  corresponding  hydroxy-acids. 

When  the  hydroxy-acids  are  heated  with  hydrogen  sulphide,  they  furnish 
the  corresponding  fatty  acids. 

GLYCOLLIC  ACID  (Hydroxy  acetic  or  Ethanoloic  Acid),  OH  •  CH2  •  COOH,  crystal- 
lises in  needles  or  plates  melting  at  80°,  and  is  soluble  in  water,  alcohol,  or  ether.  In 
nature  it  is  found  in  immature  eggs  and  in  the  leaves  of  the  wild  vine. 

It  may  be  obtained  by  the  general  methods  given  above  and  also  by  oxidising  alcohol 
or  glycol  with  dilute  nitric  acid  or  by  reducing  oxalic  a'cid  with  nascent  hydrogen.1  It  is 
usually  prepared  by  hydrolysing  monochloracetic  acid  with  KOH  [general  method  (c)]. 

1  Of  some  interest  is  the  formation  of  the  various  anhydrides  of  glycollic  acid,  these  being 
formed  by  the  removal  of  1  mol.  of  H2O  from  2  mols.  of  the  acid  as  follows  : 

(1)  From    the    two   alcohol   groups,   giving   a    true    ether   with    two   free    acid   groups, 
OTT      POOTT 

•  COOH'  di$ycollic  acid>  ni.-pt.  148°  ;  (2)  from  the  two  carboxyl  groups  ;  this  should  give 


OTT  •  OTT    •  OO 
the  anhydride  of  glycollic  acid,  QTT  .  X^-2  .  prp^'  w^ch  *s  not  3^  ^nown  5   (•*)  from  one  alcohol 

OTTT  f  (*TT     •  OO 

and  one  acid  group,  giving  a  true  ester,  glycolglycottic  acid,  PQQJI  2.  njj  ^*0.  Also  loss  of  2H20 
from  the  two  alcoholic  and  acidic  groups  gives  either  (1)  Diglycollic  anhydride  (anhydride  and 
ether  at  the  same  time),  0<^2  ]  QQ>O  (melting  at  97°  and  boiling  at  240°),  or,  when  each 
molecule  of  water  separates  from  1  alcoholic  and  1  acidic  group,  (2)  the  isomeric  glycollide, 

'  melfcing  at  86°- 


GLYCOCOLL  385 

According  to  Ger.  Pats.  194,038  and  204,787,  glycollic  acid  is  now  prepared  industrially 
by  reducing  oxalic  acid  electrolytically  in  the  following  manner :  The  cathodic  liquid 
consists  of  a  solution  of  7  parts  of  crystallised  oxalic  acid  in  33  parts  of  water  and  1 1  parts 
of  concentrated  sulphuric  acid,  while  the  anodic  liquid,  separated  by  means  of  a  diaphragm, 
is  30  per  cent,  sulphuric  acid ;  the  electrodes  are  of  lead  and  the  current  density  26-250 
amperes  per  sq.  metre  of  cathode  surface.  According  to  Ger.  Pat.  257,878  (1912)  the  acid 
may  be  prepared  also  by  heating,  for  eight  to  nine  hours  at  175°  to  200°  in  an  autoclave  fitted 
with  a  stirrer,  about  30  parts  of  trichloroethylene,  50  parts  of  quicklime,  and  250  parts  of 
water,  with  traces  of  copper  salts  as  catalyst ;  with  caustic  soda  the  reaction  is  more  rapid  : 

C2HC13  +  4NaOH  =  H20  +  3NaCl  +  OH  •  CH2  •  CO2Na. 

Glycollic  acid  is  now  used  with  advantage  to  replace  tartaric  acid  in  textile  printing, 
as  it  has  a  greater  solvent  action  on  tannates  of  dyestuffs,  which  hence  penetrate  the  fabric 
better  and  give  more  stable  colours  without  injuring  the  fibre.  The  ammonium  salt  of 
glycoilic  acid  serves  to  fix  dyes  on  wool,  while  the  aluminium  and  tin  salts  are  used  in 
alizarin  and  alizarin  orange  printing  (1914). 

Glycollic  acid  forms  a  calcium  salt,  (OH  •  CH2  •  COO)2Ca  -j-  3H20,  insoluble  in  water. 
The  most  important  derivative  of  glycollic  acid  is 

GLYCOCOLL  (Glycine  or  Aminoacetic  or  Aminoethanoic  Acid),  COOH  •  CH2  •  NH2, 
which  is  the  first  member  of  the  amino-acid  series  so  important  to  vegetable  physiology. 
It  is  obtained,  together  with  secondary  products,  by  the  action  of  concentrated  ammonia 
solution  on  monochloracetic  acid  : 

CH2C1  •  COOH  +  2NH3  =  NH4C1  +  NH2  •  CH2  •  COOH. 

It  is  always  formed  in  the  decomposition  of  hippuric  acid  (benzoylglycocoll)  with  HC1, 
or  by  the  action  of  acid  or  alkali  on  gelatine. 

It  may  also  be  obtained  by  the  reduction  of  ethyl  cyanocarboxylate  by  means  of  nascent 
hydrogen  or  from  cyanogen  and  boiling  hydriodic  acid. 

Its  homologues  are  prepared  synthetically  in  various  ways,  e.  g.,  by  treating  aldehyde- 
ammonias  with  hydrocyanic  acid  and  hydrolysing  the  amino-cyanides  thus  obtained 
with  HC1. 

Glycocoll  crystallises  in  rhombic  columns  soluble  in  4  parts  of  water  but  insoluble 
in  alcohol  or  ether ;  it  has  a  sweetish  taste  and  melts  and  decomposes  at  230°. 

The  fact  that  the  amino  -group  cannot  be  expelled  by  hydrolysis  establishes 
the  structure  of  glycocoll.  It  behaves  as  both  acid  and  base,  forming  salts 
with  acids  and  also  with  bases.  Its  copper  salt  separates  in  large,  dark  blue 
needles  on  dissolving  cupric  oxide  in  hot  glycocoll  solution  :  (C2H402N)2Cu  -f 
H2O.  With  ferric  chloride  it  gives  an  intense  red  coloration.  When  heated 
with  baryta,  it  loses  C02,  forming  methylamine;  with  nitrous  acid  it  gives 
glycoJlic  acid. 

Various  alkyl  and  other  derivatives  have  been  obtained  synthetically  from 
glycocoll : 

CH2  •  NH  •  COCH3  CH2  •  NH  •  CH3  CH2— N(CH3)3 

I  ;      I  ;       I       I 

COOH  COOH  CO— 0 

Aceturic  acid  Sarcosine  Betaine 

(derived  from  caffeine  and  from  creatine)  (from  the  beet) 

With  nitrous  acid,  the  esters  of  glycocoll  yield  ETHYL  DIAZOACETATE, 

N\ 
NH2  •  CH2  •  COO  •  C2H5  +  HN02  =  2H20  +  ||  >CH  •  COOC2H,,    which    is    a 

W 

yellow  oil  boiling  at  141°  and  readily  decomposes  and  reacts  with  evolution 
of  nitrogen ;  it  serves  for  the  synthesis  of  pyrazole. 

LACTIC  ACIDS,   OH  .  C2H4  .  CO2H 

The  two  structural  isomerides  foreseen  by  theory  are  known:    a-  and 
/3-hydroxypropionic    acids.      Also    the    a-acid   exists   in   two    stereoisomeric 
VOL.  IT.  25 


386  ORGANIC    CHEMISTRY 

forms  (I  —  laevo-  and  d  =  dextro-rotatory)  owing  to  the  presence  of  an 
asymmetric  carbon  atom  (p.  19)  and  in  an  inactive  form  (i  =  inactive),  con- 
sisting of  a  mixture  in  equal  proportions  of  the  two  stereoisomerides.  These 
lactic  acids  form  anhydrides  similar  to  those  of  glycollic  acid  (see  above). 

The  lactic  acids  give  Uffelman's  reaction,  that  is,  they  cause  the  amethyst- 
coloured  solution  obtained  on  adding  a  drop  of  ferric  chloride  to  a  dilute  salicylic 
acid  solution  to  turn  yellow ;  this  reaction  is  given  also  by  citric,  oxalic,  and 
the  tartaric  acids. 

(1)  i-ETHYLIDENELACTIC  ACID  (I  +  d)  (2-Propanoloic  or  a-Hydroxy- 
propionic  Acid  or  Ordinary  Lactic  Acid  of  Fermentation),  CH3  •  CH(OH)  •  COOH, 
is  found  in  milk  rendered  acid  by  the  action  of  the  lactic  acid  bacillus  (see 
Fig.  116,  p.  145),  in  milk-sugar  (also  cane-  and  grape-sugars,  gum,  starch,  etc.) 
which  undergoes  acid  fermentation  (lactic  fermentation)  even  in  absence  of 
air,  although  oxygen  facilitates  the  change.  Cabbage  fermented  with  vinegar 
and  salt  (Sauerkraut),  gastric  juice,  putrefied  cheese,  fresh  fodder  siloed,  and 
fermented  muscular  juices  and  the  brain  1  also  contain  free  lactic  acid. 

When  pure  it  melts  at  18°  and  boils  at  120°  under  12  mm.  pressure,  but 
usually  it  forms  a  dense  syrup  soluble  in  water,  alcohol,  or  ether.  It  is  opti- 
cally inactive,  as  it  consists  of  a  racemic  mixture  of  dextro-  and  laevo-acids 
(see  p.  21).  The  two  modifications  may  be  separated  by  crystallisation 
of  the  strychnine  salts  or  by  cultivating  in  the  solution  Penicillium  glaucum, 
which  first  destroys  the  laevo-acid  (see  p.  23).  When  heated,  the  active  acid 
is  transformed,  to  the  extent  of  one-half,  into  the  optical  enantiomorph,  so 
that  the  inactive  racemic  acid  is  obtained.  If  kept  in  a  desiccator,  it  is  partly 
converted  into  anhydride  owing  to  loss  of  water.  When  distilled  under  reduced 
pressure,  it  yields  water,  carbon  dioxide,  and  lactide  (see  above).  If  heated 
with  dilute  sulphuric  acid  it  decomposes,  like  many  other  a-hydroxy-acids, 
into  acetaldehyde  and  formic  acid. 

PREPARATION.     Of  the  various  processes  for  the  preparation  of  lactic  acid,2  only 

1  It  appears  now  to  be  proved  that  the  lactic  acid  in  the  human  organism  is  formed   in 
proportion  to  the  muscular  and  cerebral  work,  and,  together  with  carbon  dioxide,  which  is  also 
a  waste  product  of  the  cells  of  the  organism  during  wakefulness,  produce*  sleep.     While  we  sleep, 
the  blood  carries  off  these  waste  products  more  easily,  the  cells  then  recovering  their  function 
and  their  sensibility.     The  connection  between  sleep  and  fatigue  is  well  known,  and  is  shown 
not  only  by  the  fact  that  after  great  muscular  or  cerebral  fatigue  sleep  is  more  profound,  but 
by  the  results  of  the  following  experiment :  if  the  blood  of  a  very  tired  dog  is  injected  into  the 
veins  of  another  dog  in  a  normal  state,  this  dog  soon  exhibits  signs  of  great  fatigue  and  goes  to 
sleep ;  these  results  are  not  observed  if  the  blood  injected  is  that  of  a  non-fatigued  dog.     During 
heavy  muscular  labour,  the  air  expired  contains  more  C02  than  in  a  state  of  repose  and  more 
still  than  during  sleep.     The  carbon  dioxide  diminishes  the  oxygen  so  much  needed  by  the 
muscles  and  brain,  so  that  the  activity  of  these  remains  depressed.     As  is  well  known,  lactic 
acid  has  a  depressing  action  on  the  nervous  cells,  injection  of  the  acid  into  the  veins  of  any  person 
inducing  symptoms  of  fatigue  and  sleepiness  and  finally  sleep.     The  continuance  of  sleep  is  due 
to  the  fact  that  the  blood  flows  more  slowly  to  the  brain,  to  which  it  hence  carries  less  oxygen. 
It  appears,  indeed,  to  be  proved  that  in  general  five  or  six  hours'  sleep — very  deep  for  two 
hours — is  sufficient  for  the  blood  to  wash  away  these  waste  products  of  active  cellular  work  and 
to  restore  activity  to  all  the  cerebral  centres. 

2  Kiliani  treats  500  grams  of  inverted  sugar  with  250  grams  of  water  and  15  grams  of  sulphuric 
acid  at  50°  to  60°  for  two  hours,  and  then  adds  gradually  400  c.c.  of  concentrated  caustic  soda 
solution  (1:1),  the  liquid  being  kept  boiling  meanwhile. 

The  soda  is  subsequently  neutralised  with  50  per  cent,  sulphuric  acid  and  the  solution  left 
for  twenty -four  hours  to  deposit  crystalline  sodium  sulphate.  The  lactic  acid  is  extracted  with 
alcohol — which  does  not  dissolve  the  sulphate — the  alcohol  being  recovered  by  distillation. 
The  crude  lactic  acid  remaining  is  diluted,  saturated  with  zinc  carbonate  and  evaporated ; 
the  zinc  lactate  is  then  allowed  to  separate,  and  is  filtered  off,  redissolved  in  hot  water  and 
decomposed  with  H2S.  After  filtration,  the  liquid  is  concentrated  in  vacua,  pure  lactic  acid 
being  thus  obtained. 

Various  other  methods  have  been  tried.  For  instance,  3  kilos  of  cane-sugar  and  15  grams 
of  tartaric  acid  are  dissolved  in  13  litres  of  boiling  water.  In  a  few  days'  time,  after  the  cane- 
sugar  has  been  converted  into  glucose  and  levulose,  4  litres  of  acid  milk  and  100  grams  of  putre- 
fied cheese  (also  1-5  kilos  of  zinc  carbonate  to  fix  the  lactic  acid,  which  otherwise  would  arrest 
the  lactic  fermentation)  are  added  and  the  mixture  left  for-a  week  at  a  temperature  of  40°  to 


LACTIC    ACID  387 

that  used  industrially  on  a  large  scale  will  be  described,  since  for  some  years  the  manu- 
facture from  whey  has  been  abandoned  owing  to  the  low  yields,  the  difficulty  of  eliminating 
the  salts  and  various  organic  compounds,  and  the  facility  with  which  contamination  by 
butyric  organisms  occurs. 

Use  is  now  always  made  of  starchy  materials,  especially  of  potato  starch,  which  is 
intimately  mixed  with  two  parts  of  cold  water,  the  mixture  being  well  stirred  and  treated 
with  six  parts  of  boiling  water  until  a  slightly  opalescent  liquid  free  from  even  the  smallest 
lumps  is  obtained.  The  mass  is  cooled  in  a  vat  to  60°  and  treated  with  the  diastase  solution 
(green  malt  equal  in  amount  to  15  per  cent,  of  the  weight  of  the  starch  is  macerated  and 
occasionally  shaken  during  three  hours  with  four  times  its  weight  of  water  at  the  ordinary 
temperature,  the  filtered  liquid  then  containing  the  diastase);  the  saccharification  of  the 
starch  is  carried  out  at  55°  to  60°  and  finally  at  65°,  until  the  iodine  reaction  for  starch  fails. 
The  wort  thus  obtained  (see  also  :  Manufacture  of  Alcohol,  pp.  143,  201 )  is  treated  with 
50  per  cent,  of  powdered  calcium  carbonate,  5  per  cent,  (on  the  weight  of  the  starch)  of 
sterilised  skim  milk  and  with  wort  (1  litre  per  100  litres)  from  a  vat  in  which  a  pure  lactic 
acid  organism  (a  little  Bacillus  Delbriicki  may  be  added)  is  actively  developing.  The 
temperature  is  kept  at  40°  to  50°,  and  the  mass  is  vigorously  mixed  two  or  three  times  per 
day  so  that  the  lactic  acid  may  be  fixed  by  the  calcium  carbonate ;  after  a  week  crusts  of 
calcium  lactate  begin  to  separate.  The  fermentation  is  continued  for  three  to  four  days 
longer,  until  indeed  a  sample  of  the  liquid,  freed  from  chalk  and  carbonic  acid,  ceases  to 
reduce  Fehling's  solution  (see  later:  Sugars). 

This  fermentation  consists  solely  of  a  decomposition,  C6H1206  =  2C3H6O3,  and  is 
accompanied  by  neither  generation  of  C02  nor  absorption  of  water. 

In  the  fermenting  rooms  the  greatest  cleanliness  is  necessary,  in  order  to  prevent 
infection  with  extraneous  bacteria.  If  such  infection  (recognisable  by  the  bad  smell  and 
by  lack  of  the  crystalline  crusts  of  calcium  lactate,  so  that  fine  granules  of  calcium  carbonate 
alone  are*  visible  when  the  liquid  is  stirred)  does  occur  in  any  vat,  the  contents  of  the 
latter  should  be  boiled  to  sterilise  it  and  the  lactic  fermentation  again  started  at  55°  to  60°. 

45°,  by  which  means  the  maximum  production  of  lactic  acid  is  obtained.  The  acid  separates 
as  zinc  lactate  in  crystalline  crusts  which,  after  purification  (by  recrystallisation ),  are  suspended 
in  water  and  decomposed  with  H2S  in  order  to  remove  the  zinc  as  insoluble  sulphide.  The 
filtered  liquid  is  concentrated  to  a  syrupy  consistency  and  then  extracted  with  ether,  which  does 
not  dissolve  the  impurities  (zinc  salts,  mannitol,  etc.);  on  evaporation  of  the  ether,  pure  syrupy 
lactic  acid  is  obtained.  Besides  the  decomposition  of  the  sugar,  various  secondary  reactions 
always  accompany  lactic  fermentation,  and  the  yield  of  the  acid  is  scarcely  20  per  cent,  of  the 
weight  of  the  sugar  taken. 

A  better  yield  is,  however,  obtained  by  Larrieu's  process  (Fr.  Pat.  206,506),  which  consists 
in  treating  starch  paste  with  malt  and  hot  water  (as  in  the  ordinary  industrial  process). 

Jacquemin  prepares  the  acid  from  worts  similar  to  those  employed  in  breweries  (barley 
mashed  at  50°  with  malt,  then  boiled  to  destroy  the  diastase  and  cooled  to  45°)  by  the  addition 
of  pure  lactic  ferment  and  calcium  carbonate.  After  five  to  six  days,  the  mash  is  filtered  and 
concentrated,  the  calcium  lactate  being  then  decomposed  in  the  usual  way  with  sulphuric  acid. 

Dreher  works  in  a  similar  manner,  but  with  glucose  solutions  containing  1  per  cent,  of  nutrient 
substances  for  the  ferment  (e.g.,  sodium  phosphate,  nitre,  salt,  etc.). 

Industrially,  however,  lactic  acid  was  formerly  always  obtained  from  milk  residues  (whey 
or  molasses  of  milk-sugar,  which  remain  after  the  removal  of  the  butter  from  the  milk  in  the 
separator;  also  cheese  by  coagulation  with  rennet  in  the  hot).  The  whey  is  concentrated  in 
open  vessels  or,  better,  in  vacuum  pans,  to  16°  Be.,  and  is  then  introduced  into  wooden  vessels 
in  which,  at  a  temperature  of  40°,  the  lactic  ferment  is  added  in  the  form  either  of  part  of  the 
liquid  from  a  previous  fermentation  or  of  putrefied  cheese.  Powdered  chalk  is  added  to  neutralise 
the  acid  formed,  the  liquid  being  stirred  from  time  to  time  and  the  fermentation  allowed  to 
continue  for  ten  to  twelve  days.  After  decantation,  the  calcium  lactate  is  decomposed  with  dilute 
sulphuric  acid,  the  liquid  mass  being  well  mixed,  and  the  iron  separated  if  necessary  by  means 
of  potassium  ferrocyanide.  In  some  cases,  before  the  calcium  lactate  is  decomposed,  it  is 
separated  by  concentrating  the  solution,  and  is  recrystallised  from  a  little  hot  water,  which 
should  dissolve  20  per  cent,  of  it,  and  then  treated  as  usual  with  dilute  sulphuric  acid.  The 
calcium  sulphate  formed  is  removed  by  passing  the  mass  through  a  filter-press  (see  figure  in  the 
section  on  Sugar)  and  the  clear  lactic  acid  solution  concentrated  in  a  double-  or  triple-effect 
apparatus  until  it  attains  a  concentration  of  50  per  cent.  The  further  small  quantity  of  gypsum 
which  is  then  deposited  is  separated  by  filtration,  the  resulting  yellowish-brown  liquid  repre- 
senting commercial,  crude,  50  per  cent,  (by  weight)  lactic  acid.  This  should  not  contain  more 
than  1-5  per  cent,  of  ash,  and  should  not  contain  sulphate  or  reduce  Fehling's  solution. 

The  lactic  acid  prepared  from  the  molasses  of  milk-sugar  factories  is  more  impure  than  the 
above. 

Lactic  acid  is  also  obtained  (1905)  from  a  mixture  of  bran  and  barley. 


388  ORGANIC    CHEMISTRY 

At  the  end  of  the  fermentation  the  liquid  is  rendered  alkaline  by  addition  of  milk  of 
lime,  boiled  with  decolorising  charcoal,  and  filtered  hot  through  filter-presses,  the  calcium 
lactate  crystallising  out  on  cooling  (in  some  factories  the  calcium  lactate  solution  is  decom- 
posed directly  by  means  of  sulphuric  acid,  the  liquid  being  boiled  with  charcoal  and  potas- 
sium ferrocyanide — to  expel  iron — filtered  and  boiled  to  syrupy  lactic  acid).  The  calcium 
lactate  crystals  are  collected  in  a  vacuum-filter,  the  mother-liquors  being  reconcentrated 
and  the  crystals,  dissolved  in  boiling  water,  treated  with-  pure  sulphuric  acid  until  the 
liquid  colours  Congo  red  paper  deep  violet  (showing  excess  of  mineral  acid)  and  filtered  to 
remove  the  calcium  sulphate.  The  colourless  liquid  is  concentrated  in  a  vacuum  apparatus 
(lead-lined  or  enamelled)  to  a  strength  of  50  per  cent.  The  wash- waters  from  the  calcium 
sulphate  serve  for  making  the  milk  of  lime.  From  100  kilos  of  starch  135  kilos  of  com- 
mercial 50  per  cent,  lactic  acid  is  obtainable,  but  this  contains  also  other  organic  acids 
and  at  200°  leaves  a  residue  of  5  to  6  per  cent. ;  with  further  purification  the  yield  diminishes. 
If  the  heating  is  too  prolonged  during  the  concentration,  lactide  is  formed  to  some  extent. 

Very  pure  lactic  acid  is  obtained  by  extracting  the  crude  product  with  ether  or  amyl 
alcohol — which  does  not  dissolve  the  impurities  (sugar,  gum,  mineral  substances) — and 
steam-distilling  in  vacuo. 

An  English  patent  (No.  26,415,  1907)  describes  the  preparation  of  pure,  concentrated 
lactic  acid  by  the  distillation  of  the  commercial  50  per  cent,  acid  in  a  rapid  current  of  air 
or  of  an  indifferent  gas. 

In  some  cases  purification  is  effected  by  crystallisation  of  the  zinc  salt. 

USES.  Until  a  few  years  ago  the  uses  of  lactic  acid  were  limited  to  the  preparation 
of  soluble  lactates  for  medicinal  purposes,  but  its  manufacture  has  recently  been  con- 
siderably extended  owing  to  its  employment  in  the  dyeing  of  wool,  silk,  etc.,  in  place  of 
tartaric  acid,  tartar  and  oxalic  acid  for  the  reduction  of  the  chromium  compounds  with 
which  wool  to  be  treated  with  fast  dyes  (alizarin  dyes,  etc. )  is  mordanted.  For  the  same 
reasons  it  is  advantageously  employed  in  the  chrome  tanning  of  skins,  its  value  in  this 
case  being  sometimes  regarded  as  due  to  its  ability  to  keep  calcium  salts  in  solution  and 
thus  prevent  the  formation  of  certain  white  harmful  deposits. 

The  crude  50  per  cent,  acid  is  most  commonly  sold,  and  it  is  necessary  to  ascertain 
whether  by  50  per  cent,  is  meant  50  kilos  per  100  litres  or  per  100  kilos  of  solution;  in  the 
former  case  the  strength  of  the  acid  is  only  43  per  cent,  by  weight  (L  e.,  100  kilos  contain 
43  kilos  of  acid). 

Commercial,  brown,  50  per  cent,  lactic  acid  cost  about  32s.  per  cwt.  before  the  war; 
the  paler,  yellow  product  of  the  same  strength,  52s. ;  the  pure  (sp.  gr.  1-21 ),  3s.  Id.  per  kilo, 
and  the  chemically  pure,  12s.  per  kilo. 

Before  the  war  importation  of  lactic  acid  into  Italy  was  subject  to  a  duty  of  6s.  per 
cwt.  The  amounts  of  the  Italian  imports  and  exports  are  as  follows  (tons) : 

w     1908    1910   1912   1913    1914     1915     1916    1917     1918 

Importation  .     65        49        40        51        40        10-7        0-9        0-8         0-2 

Exportation  .  4-8       4-6       0-5          8  0-1 

French  importation    -  155       156         72  89 

Before  the  war  Germany  exported  the  following  quantities  of  lactic  acid  and 
lactates : 

1909        1910        1911        1912        1913 

Tons      .         .         .     1044  1278  1807  1771  2049 

Salts  of  Lactic  Acid  are  generally  soluble  to  some  extent  in  water.  Calcium  lactate, 
(C3H503)2Ca  -f  5H20,  forms  mammillary  aggregates  of  white  needles  soluble  in  9-5  parts 
of  cold  water,  and  in  all  proportions  in  boiling  water ;  it  is  insoluble  in  cold  alcohol.  The 
water  of  crystallisation  is  evolved  in  a  vacuum  desiccator  or  on  heating  to  100°.  At  250° 
it  loses  H2O,  giving  calcium  dilactate,  which  is  less  soluble  in  alcohol  than  the  original  salt. 

Calcium  lactophosphate,  obtained  by  neutralising  lactic  acid  with  gelatinous  calcium 
phosphate,  dissolves  to  some  extent  in  water  and  is  used  for  treating  rickets  and  diseases 
of  the  bones.  Ferrous  lactate,  (C3H503)2Fe  +  3H2O,  is  obtained  by  treating  boiling  aqueous 
calcium  lactate  solution  with  ferrous  chloride  solution,  greenish- yellow  crystals  separating 
on  cooling ;  it  is  used  in  medicine.  Zinc  lactate  crystallises  with  3H20. 


HYDROXY-ACIDS  389 

'  ALANINE,  CH3  •  CH(NH2)  •  COOH,  is  obtained  from  the  corresponding  aldehyde- 
ammonia  by  the  action  of  hydrocyanic  acid.  From  the  inactive,  synthetic  compound, 
the  active  stereoisomerides  are  separated  by  means  of  the  strychnine  or  brucine  salts. 
The  action  of  PC15  expels  both  the  hydroxyl-  and  the  amino-groups,  giving  lactyl  chloride, 
CH3  •  CHC1  •  COC1,  which  gives  a-chlorpropionic  acid,  CH3  •  CHC1  •  COOH,  when  treated 
with  water. 

(2)  d-ETHYLIDENELACTIC  ACID  (Paralactic  or  Sarcolactic  Acid)  differs  from 
ordinary  lactic  acid  only  in  the  greater  solubility  of  its  zinc  salt  (+  2H2O),  and  the  less 
solubility  of  its  calcium  salt  (+  4H20).     It  is  found  in  Liebig's  extract  of  meat,  and  it  is 
contained  in  the  muscular  juices,  and  is  also  formed  in  certain  lactic  fermentations. 

(3)  J-ETHYLIDENELACTIC  ACID  is  formed  during  the  fermentation  of  aqueous 
cane-sugar  solutions  by  Bacillus  acidi  Icevolactici. 

(4)  ETHYLENELACTIC  ACID  (Hydracrylic,  /3-Hydroxypropionic  or  3-Propanoloic 
Acid),  OH  •  CH2  •  CH2  •  COOH,  differs  from  its  isomerides  in  that,  when  heated,  it  loses  a 
molecule  of  water,  giving,  not  the  anhydride,  but  acrylic  acid,  CH2  :  CH  •  C02H.     Further, 
with  oxidising  agents  it  gives,  not  acetic  acid,  but  oxalic  acid  and  carbon  dioxide.     It  con- 
tains no  asymmetric  carbon  atom  and  is  hence  optically  inactive.    It  may  be  prepared 
synthetically  from  (1)  /3-iodopropionic  acid,  or  (2)  ethylene,  CH2 :  CH2,  by  addition  of 
hypochlorous  acid,  giving  OH  •  CH2  •  CH2C1,  which  is  then  converted  into  the  nitrile 
OH  •  CH2  •  CH2  •  CN,  hydrolysis  of  the  latter  giving  ethylenelactic  acid.     The  acid  is  a 
colourless,  syrupy  liquid  and  forms  a  calcium  salt    (+  2H2O)  and  a  readily  soluble  zinc 
salt  (+  4H2O). 

HYDROXYBUTYRIC  ACIDS,   OH  •  C3H6  •  CO2H 

Five  isomerides  are  theoretically  possible,  four  being  known :  two  a-acids,  one  fi-acid, 
and  one  y-acid  (prepared  only  as  salts ). 

a-HYDROXYBUTYRIC  ACID,  CH3  •  CH2  •  CH(OH)  •  C02H,  melts  at  43°  and  is  syn- 
thesised  as  the  inactive,  racemic  form,  which  may  be  resolved  into  its  active  components 
by  means  of  brucine  (see  p.  23). 

a-HYDROXYISOBUTYRIC  ACID  (Acetonic  or  2-Methyl-2-propanoloic  Acid), 
OH  •  C(CH3)2  .  CO2H,  melts  at  79°,  boils  at  212°,  and  is  obtainable  by  various  synthetical 
methods  from  dimethylacetic  acid,  acetocyanohydrin,  a-aminobutyric  acid,  etc. 

^-HYDROXYBUTYRIC  ACID,  CH3  •  CH(OH)  •  CH2  •  CO2H,  is  obtained  by  oxidising 
aldol  or  reducing  acetoacetic  acid,  these  methods  of  formation  indicating  its  constitution. 
It  forms  a  syrup  and  its  Isevo-isomeride  is  found  in  the  blood  and  in  diabetic  urine. 

HIGHER   HYDROXY-ACIDS 

a-HYDROXYVALERIC  ACID,  CH3  •  CH2  •  CH2  •  CH(OH)  •  CO2H,  melts  at  29°. 
a-HYDROXYISOVALERIC  ACID,  (CH3)2CH  •  CH(OH)  •  CO2H,  melts  at  86°. 

PT-T  OH 

METHYLETHYLGLYCOLLIC  ACID,  riil>C<Jv?tn  melts  at  68°. 

^25  UvJjjrl 

a-HYDROXYCAPROIC  ACID  (Leucinic  Acid),  CH3  •  [CH2]3  •  CH(OH)  •  C02H,  melts 
at  73°  and  is  obtained  from  leucine  (see  later). 

a-HYDROXYMYRISTIC  ACID,  CH3  •  [CH2]U  •  CH(OH)  •  CO2H,  melts  at  51°. 

a-HYDROXYPALMITIC  ACID,  CH3  .  [CH2]13  .  CH(OH)  •  CO2H,  melts  at  82°. 

a-HYDROXYSTEARIC  ACID,  CH3  •  [CH2]15  •  CH(OH)  •  CO2H,  melts  at  84°  to  86°, 
and  is  formed  by  the  action  of  cold  concentrated  sulphuric  acid  on  oleic  acid,  this  method 
being  sometimes  used  practically  to  prepare'solid  fatty  acids  from  liquid  oleic  acid  (see 
section  on  Fats). 

The  Sulphuric  Ether  of  a-Hydroxystearic  Acid,  C18H35O2(OSO3H),  is  used  in  the 
dyeing  of  cotton  with  Turkey- red  (see  below). 

Various  other  yS-hydroxystearic  and  dihydroxystearic  acids,  with  melting-points  higher 
than  those  of  the  liquid  fatty  acids  which  yield  them,  are  also  known. 

B.     MONOBASIC   UNSATURATED    HYDROXY-ACIDS 

The  a-Hydroxyolefinecarboxylic  Acids  are  prepared  by  hydrolysing,  with  HC1  in  the 
cold,  the  nitriles  obtained  by  the  addition  of  hydrogen  cyanide  to  olefinic  aldehydes. 
If  the  double  linking  (A)  is  in  the  y8y-position,  these  hydroxy-acids  are  converted  into 


390  ORGANIC    CHEMISTRY 

y-ketocarboxylic  acids  when  boiled  with  dilute  HC1;    thus,  a-hydroxypentenoic  acid, 
CH3  •  CH  :  CH  •  CH(OH)  •  CO2H,  yields  levulinic  acid,  CH3  •  CO  •  CH2  •  CH2  •  C02H. 

Several  /?-Hydroxyolefinecarboxylic  Acids  are  known.  The  most  simple  is  /3- 
hydroxyacrylic  or  formylacetic  acid,  CO2H  •  CH  :  CH  •  OH,  which,  like  the  others,  readily 
forms  esters  and  halogen  derivatives. 

y-  and  S-Hydroxyolefinecarboxylic  Acids  are  known  mostly  in  the  form  of  lactones 
(see  pp.  355  and  384). 

RICINOLEIC  ACID  (Hydroxyoleic  Acid),  C18H34O3,  or  CH3  •  [CH2]5  •  CH(OH)2 
CH2  •  CH  :  CH  •  [CH2]7  •  CO2H,  constitutes,  in  the  form  of  glyceride,  the  greater  proportion 
of  castor  oil,  and,  on  dry  distillation  under  reduced  pressure,  decomposes  into  oananthal- 
dehyde,  C7H14O,  and  undecylenic  acid,  CnH20O2.  It  solidifies  at  —  6°  and  melts  at 
+  4°.  It  forms  lead  and  barium  salts  soluble  in  ether,  and,  when  fused  with  KOH,  yields 
sebacic  acid,  C8H16(C02H)2,  and  sec.  octyl  alcohol.  It  forms  a  solid  bromide  and  an  oily 
ozonide  (by  the  addition  of  ozone)  which  decomposes,  giving,  among  other  products,  a 
large  proportion  of  azelaic  acid  (Molinari  and  Caldana,  1909),  the  position  of  the  double 
linking — established  by  Goldsobel  (1894)  by  means  of  ricinostearolic  acid — being  thus 
confirmed.  By  nitrous  acid  it  is  transformed  into  the  isomeric  ricinelaidinic  acid,  melting 
at  53°.  By  decomposing  the  ozonide  of  methyl  ricinoleate,  Haller  and  Brochet  (1910) 
obtained  /3-hydroxypelargonic  acid,  CH3  •  [CH2]5  '  CH(OH)  •  C02H,  azelaic  acid  and  the 
corresponding  semi-aldehyde.1 

By  treating  castor  oil  slowly  with  cold,  concentrated  sulphuric  acid,  ricinosulphuric 
acid  is  obtained,  this  being  the  most  important  constituent  of  Turkey-red  oil,  which  is 
used  in  large  quantities  in  the  dyeing  and  printing  of  cotton  textiles  with  alizarin  red 
(Adrianople  red).2  It  is  also  used  for  greasing  wool  to  be  spun  and  for  dressing  textiles. 

1  Ricinoleic  Acid  was  prepared  pure  by  Krafft  (1888)  by  hydrolysing  castor  oil,  the  fatty 
acids  thus  obtained  being  cooled  at  0°  and  the  solid  acids  separated  by  squeezing  (at  10° ).    The 
dry  lead  or  barium  salt  was  then  prepared  and  extracted  with  ether,  which  leaves  undissolved 
the  last  traces  of  the  salts  of  the  solid  fatty  acids ;   the  salt  of  ricinoleic  acid  is  dissolved  and 
gives  the  pure  acid. 

With  concentrated  sulphuric  acid,  the  acid  gives  (Benedikt  and  Ulzer,  1887;  Juillard,  1894 
and  1895;  Chonowsky,  1909,  and  especially  Ad.  Griin,  1906  and  1909)  ricinoleinsulphonic  acid 
C17H32(0  •  S03H)  •  C02H;  by  hot  water  this  acid  is  hydrolysed  with  separation  of  sulphuric 
acid  and  formation  of  a  condensed  ester  (ricinoleinricinoleic  esler),  C17H32(OH)  •  CO  •  0  •  C17H32  • 
C02H,  the  condensation  taking  place  between  the  carboxyl  group  of  one  molecule  and  the 
hydroxyl  of  another;  only  one  acetyl  group  is  introduced  into  the  molecule  of  this  compound 
by  the  action  of  acetic  anhydride.  Various  isomeric  condensed  anhydrides  of  dihydroxystearic 
acids  are  also  easily  prepared:  these  are  solid  and  have  the  constitution  C17H33(OH)2  •  CO  • 
O  •  C17H33(OH)  •  C02H  (4  isomerides)  and  may  be  converted  into  the  corresponding  dihydroxy- 
stearic acids.  One  of  the  latter  melts  at  90°  and  is  optically  active  ([a]o  =  +  6-45°),  two  melt 
at  69-5°  and  108°  respectively  and  are  inactive,  while  the  fourth  melts  at  126°  and  is  active; 
the  positions  of  the  two  hydroxyl  groups  seem  to  be  9  and  12,  or  10  and  12  (for  those  with  the 
higher  melting-points). 

The  action  of  sulphuric  acid  on  olive  oil  partly  decomposes  the  triolein  into  glycerol  and 
oleic  acid  and  partly  transforms  it  only  into  diolein.  To  some  extent  the  double  linking  of 
oleic  acid  fixes  H20  and  forms  hydroxystearic  acid,  which  is  partly  converted  into  the  sulphuric 
ester  of  1  :  10 -dihydroxystearic  acid.  Besides  free  ricinoleic  acid,  undecomposed  glycerides 
and  glycerol,  Turkey-red  oil  contains  (according  to  Juillard),  the  sulphuric  ester  of  ricinoleic 
acid,  dihydroxystearic  acid  and  the  two  corresponding  mono-  and  cli -sulphuric  esters,  as  well  as 
diricinoleic  acid  and  other  polymerides  (up  to  pentaricinoleic  acid). 

The  phenomenon  of  polymerisation  is,  indeed,  of  great  importance  as  regards  the  effects 
produced  in  practice  by  the  sulphoricinate. 

2  Turkey-Red  Oil  (or  sulphoricinate)  is  prepared  by  treating  castor  oil — in  an  open,  double- 
bottomed,  iron  vessel  furnished  with  a  stirrer — with  iO  per  cent,  (in  summer)  or  25  per  cent, 
(in  winter)  of  concentrated  sulphuric  acid  (66°  Be.),  which  is  added  very  slowly  during  five  or 
even  eight  hours,  so  that  the  temperature  of  the  mass  never  exceeds  35° ;  if  these  precautions 
are  neglected,  S02  is  evolved.    When  necessary,  the  temperature  is  moderated  by  passing 
cold  water  through  the  jacket.    The  mixture  is  left  for  some  hours  until  a  small  portion   is 
found  to  be  soluble  in  water.    The  mass  is  then  discharged  into  a  wooden  vat  containing  a 
quantity  of  sodium  chloride  or  sulphate  equal  to  that  ot  the  oil  treated.     After  mixing,  the 
liquid  is  allowed  to  stand  for  some  hours,  the  excess  of  acid  (10  to  12  per  cent,  is  fixed  in  the 
sulphoricinate)  being  next  removed  by  decanting  the  aqueous  portion  and  washing  the  remainder 
in  the  same  manner  and  afterwards  with  two  successive  quantities  of  water  half  saturated  with 
common  salt;  sufficient  concentrated  ammonia  or  sodium  hydroxide  solution  is  then  added  to 
give  a  neutral  (or  amphoteric)  reaction.     The  quantity  and  concentration  of  the  alkali  to  be 
added  are  determined  by  a  preliminary  test  on  a  small  portion,  which  gives  also  the  content 
in  fatty  acids  of  the  commercial  ricinate.     It  is  usually  a  clear,  yellowish  solution,  which  gives 


POLYVALENT    HYDROXY-ACIDS  391 

The  treatment  of  castor  oil  with  concentrated  sulphuric  acid  yields  ricinoleic  acid 
more  or  less  polymerised  or  condensed  into  anhydrides,  glycerolsulphuric  esters  of  ricinoleic 
acid  and  a  preponderating  proportion  of  ricinosulphuric  acid,  which  is  an  ester  of  sulphuric 
acid  soluble  in  water  :  C18H33O2  •  OH  +  H2SO4  =  H20  +  C18H33O2  •  O  •  SO3H.  This  acid 
is  separated  from  water  by  addition  of  salt  or  dilute  mineral  acid  in  the  cold ;  it  is  only 
slightly  soluble  in  ether,  and  its  calcium,  lead,  etc.,  salts  are  insoluble  in  water.  Ricino- 
sulphuric acid  is  not  decomposed  in  the  hot  by  water  or  dilute  alkali,  but  it  decomposes 
readily  into  sulphuric  and  ricinoleic  acids  when  boiled  with  dilute  hydrochloric  or  sulphuric 
acid.  By  using  an  excess  of  concentrated  sulphuric  acid,  Griin  (1907)  obtained  9:  12- 
dihydroxystearic  acid.  Ricinosulphuric  acid  or  its  sodium  or  ammonium  salt  is  of 
importance  in  Turkey-red  oil,  since,  when  the  latter  is  diluted  with  water,  it  serves  to 
keep  in  a  state  of  solution  the  castor  oil  or  other  unaltered  oil  always  found  in  greater  or 
larger  quantity  in  Turkey-red  oil. 

Treatment  of  olive  oil  or  oleic  acid  with  sulphuric  acid  yields  hydroxystearosulphuric 
acid,  which  is  saturated,  ClgH34O2  (oleic  acid)  +  H2S04=  G1SH3^02  •  O  •  S03H;  so  that 
the  iodine  number  may  be  used  to  distinguish  true  sulphoricinates  from  saturated  ones, 
which  are  unable  to  undergo  those  characteristic  oxidations  necessary  to  dyeing  operations. 
With  an  excess  of  sulphuric  acid,  hydroxystearosulphuric  acid  takes  up  a  molecule  of 
water,  yielding  sulphuric  acid  and  hydro  xystearic  acid  (saturated),  C18H35O.2  •  OH. 

C.     POLYVALENT   MONOBASIC    HYDROXY-ACIDS 

These  are  derived  from  polyhydric  alcohols  by  the  oxidation  of  one  primary 
alcoholic  group  to  carboxyl,  the  other  two  or  more  alcoholic  groups  remaining 
unaltered ;  they  exhibit  behaviour  analogous  to  that  of  lactic  acid.  The  number 
of  the  hydroxyls  is  deduced  from  the  acetyl  number  (see  p.  224).  These  acids, 
which  are  gelatinous  and  crystallise  with  difficulty,  are  sometimes  obtained 
by  the  gradual  oxidation  of  saccharine  substances  or  of  unsaturated  acids. 

a  clear  solution  when  diluted  with  2  to  4  vols.  of  water  and  a  milky  emulsion  when  mixed  with 
5  to  6  vols.  of  water  or  with  dilute  alkali. 

The  commonest  strengths  are  40,  50,  and  60  per  cent,  of  total  fat  (liberated  from  the  alkali), 
which  is  estimated  by  Herbig's  method  (1906);  10  grams  of  the  sulphoricinate  are  dissolved 
in  50  c.c.  of  hot  water,  25  c.c.  of  dilute  HC1  being  then  added  and  the  solution  boiled  for  four  or 
five  minutes,  during  which  time  it  is  kept  stirred  to  avoid  spurting.  It  is  next  cooled  (and, 
if  desired,  the  volume  of  the  washed  fatty  acids  may  be  measured  in  a  burette)  and  extracted 
in  a  separating  funnel  with  200  c.c.  of  ether,  which  is  washed  \\ith  three  separate  quantities 
of  15  to  20  c.c.  of  water.  The  ether  is  distilled  off  from  a  tared  flask,  the  fat  being  heated  over 
a  naked  flame  and  shaken  for  a  couple  of  minutes,  dried  at  105°  for  half  an  hour  and  weighed. 
When  neutral,  not  sulphonated,  fats  are  present,  they  are  determined  by  treating  30  grams  of 
the  sulphoricinate  with  50  c.c.  of  water,  20  c.c.  of  ammonia,  and  30  c.c.  of  glycerol,  the  whole 
being  extracted  with  ether,  which  is  washed  with  water  and  evaporated  in  a  tared  dish.  To 
ascertain  if  the  sulphoricinate  is  the  ammonium  or  sodium  compound,  tests  are  made  for  these 
bases  in  the  wash-water  separated  in  estimating  the  total  fat;  the  ammonia  is  estimated  by 
heating  with  excess  of  alkali  and  collecting  the  ammonia  in  a  standard  solution  of  sulphuric 
acid,  while  the  soda  is  determined  by  evaporating  to  dryness,  calcining  the  residue  and  weighing 
as  sodium  sulphate. 

If  the  sulphoricinate  were  not  prepared  from  castor  oil  (inferior  products  are  obtained  from 
olive  oil  with  a  larger  amount  of  sulphuric  acid ),  it  will  give  a  turbid  solution  in  alcohol,  while 
the  acetyl  number  (seep.  224)  of  the  total  fatis  only  5  to  10  (for  olive  oil),  that  of  true  sulphoricinate 
being  usually  140  and  always  above  125.  Further,  the  iodine  number  of  the  acids  of  true 
sulphoricinate  is  never  lower  than  68  to  70,  whilst  with  other  oils  it  is  decidedly  lower  than 
70.  In  the  Zeiss  oleorefractonieter  the  fatty  acids  of  pure  sulphoricinate  give  a  reading  of  74. 

The  complete  analysis  of  a  good  sulphoricinate  gave  58  per  cent,  of  total  fat  (composed 
of  47  per  cent,  of  insoluble  fatty  acids,  1-5  per  cent,  of  neutral  fats,  and  9-5  per  cent,  of  fatty 
sulpho-acids  soluble  in  water),  1-8  per  cent,  of  ammonia,  and  4-6  per  cent,  of  sulphuric  acid. 
In  true  sulphoricinates,  however,  the  ratio  of  sulphuric  to  sulphoricinic  acid  should  be  not 
4-6  :  9-5,  but  rather  4-6  :  22,  and  the  sulphuric  acid  as  sodium  or  ammonium  sulphate  should  not 
exceed  0-2  to  0-3  per  cent.  The  soluble  sulpho-acids  are  estimated  by  treating  10  grams  of  the 
total  fatty  acids  with  (not  more  than)  10  c.c.  of  ether  and  30  c.c.  of  saturated  sodium  chloride 
solution  free  from  sulphates ;  the  mixture  is  shaken  and  filtered  through  a  moist  filter,  the 
sulpho-acids  in  the  filtrate  being  precipitated  with  barium  chloride. 

The  price  of  Turkey -red  oil  is  based  on  its  content  of  total  fat  and  is  usually  about  lOd.  per 
unit  of  fat  per  100  kilos  of  sulphoricinate.  This  content  is  often  determined  in  a  graduated 
burette,  by  decomposing  a  given  quantity  of  the  sulphoricinate  with  sulphuric  acid,  diluting 
with  water  and  measuring,  in  the  burette,  the  fat  which  rises  to  the  surface  after  some  hours. 


392  ORGANIC    CHEMISTRY 

GLYCERIC  ACID  (a/3-Dihydroxypropionic  or  Propandioloic  Acid),  OH  •  CH2  •  CH 
(OH)  •  CO2H,  obtained  by  oxidising  glycerol  with  nitric  acid,  exists  in  optically  active 
forms,1  and  is  soluble  in  alcohol,  water,  or  acetone  (which  does  not  dissolve  glycerol).2 
As  has  already  been  mentioned,  dihydroxystearic  acid,  C18H34O2(OH  )2,  is  formed  by  oxidising 
oleic  acid. 

ERYTHRIC  ACID  (Butantrioloic  Acid),  OH  •  CH2  •  [CH(OH)]2  •  CO2H,  is  formed  on 
gentle  oxidation  of  fructose  or  erythritol,  and  is  monobasic  and  tetravalent. 

Of  the  pentavalent  monobasic  acids,  four  pentonic  or  pentantetroloic  isomerides, 
C4H5(OH)4  •  C02H,  are  known,  namely  :  Arabonic  acid  (by  oxidising  arabinose)  is  Isevo- 
rotatory  (—  73-9°),  melts  at  89°  and  yields  a  lactone,  C5HgO5,  m.-pt.  95°  to  98°,  when  its 
solution  is  evaporated,  d- Arabonic  acid  (+  73-7°)  melts  at  98°;  l-ribonic  acid  yields  a 
lactone,  m.-pt.  72°  to  76°.  l-Xylonic  acid  is  formed  by  prolonged  treatment  of  1-xylose 
with  bromine  water ;  if  heated  with  pyridine  it  is  converted  into  d-lyxonic  acid,  the  lactone 
of  which  melts  at  162°. 

The  group  of  saccharinic  acids  comprises  a  number  of  tetrahydroxypentancarboxylic 
acids,  which  are  readily  transformed  into  lactones  termed  saccharins  (not  to  be  confused 
with  the  saccharin  of  the  aromatic  series ). 

Saccharinic  or  hexantetroloic  acid,  C5H7(OH)4  •  C02H,  is  obtained  by  treating  glucose 
or  fructose  with  lime,  while  iso-  and  meta-  saccharinic  acids  are  also  known  in  the  free  state 
and  para- saccharinic  acid  as  salts.  The  corresponding  lactones  are  : 

CO 0 

I  I 

1.  Saccharin,  CH3  •  C(OH)  •  CH(OH)  •  CH  •  CH2  •  OH,  m.-pt.  160°,  has  a  bitter  taste. 

CO—  — O 

I  I 

2.  Isosaccharin,  OH  •  CH2  •  C(OH)  •  CH2  •  CH  •  CH2  •  OH,  melts  at  95°. 

-CO—      -0 

I  I 

3.  Metasaccharin,  OH  •  CH  •  CH2  •  CH  •  CH(OH)  •  CH2  •  OH,  melts  at  141°. 

CO—  —  O 

I  I 

4.  Parasaccharin,  OH  •  CH2  •  CH(OH)  •  C(OH)  •  CH2  •  CH2,  is  a  syrupy  liquid. 

These  lactones  are  distinguished  by  the  different  products  they  form  on  oxidation  with 
nitric  acid  or  hydrogen  peroxide. 

The  hexonic  acids  or  hexanpentoloic  acids,  C5H6(OH)5-  CO2H,  are  known  in  some  cases 
only  as  lactones  and  are  obtained  by  reduction  of  the  corresponding  dibasic  acids  (saccharic 
acid,  etc. )  or  by  gentle  oxidation  (with  bromine  water)  of  the  corresponding  sugars  (hexoses ), 
to  which  they  are  closely  related  : 

Mannose,  C6H1206,  yields  mannonic  acid,  C6H12O7. 
Galactose         „          ,,      galactonic    „  „ 

Glucose  „          ,,      gluconic       ,,  „ 

Gulose  „          „      gulonic        „  „ 

Idose  „          „      idonic          „  „ 

Talose  ,,  „      talonic         „  „ 

These  acids  may  be  obtained  synthetically  by  hydrolysing  the  nitriles  (see  pp.  237  and 
320)  of  the  simpler  sugars  (pentoses). 

1  From  the  racemic  form,   the  laevo-modification  may   be  obtained   by  fermenting  the 
ammonium  salt  with  Penicillium  glaucum,  and  the  dextro-form  by  the  direct  action  of  Bacillus 
ethaceticus. 

2  It  forms  a  calcium  salt;  (C3H504)2Ca  +  2H20,  soluble  in  water,  whilst  the  lead  salt  is 
only  slightly  soluble  in  cold  water.     Among  the  derivatives  of  this  acid  are  serine,  OH  •  CH2  • 
CH(NH2)  •  C02H,  which,  being  an  amino -derivative,  has  a  neutral  reaction  and  forms  salts  with 
both  acids  and  bases  ;  it  is  obtained  by  boiling  silk-gum  with  dilute  sulphuric  acid  and  is  soluble 
in  water  but  insoluble  in  alcohol  or  ether. 

Among  the  higher  derivatives  are  (1)  ornithine  (aS-diaminovaleric  acid),  NH2  •  CH2  •  CH2  • 
CH2  •  CH(NH2)  •  C02H,  which  is  formed  on  decomposition  of  arginine,  contained  in  germinating 
lupins,  and  (2)  lysine,  or  at-diaminocaproic  acid,  NH2  •  [CH2]4  •  CH(NH2)  •  C02H,  which  is 
obtained  on  decomposing  casein  or  glue  with  hydrochloric  acid. 


ALDEHYDIC    ACIDS  393 

Further,  the  hexonic  acids  yield  the  sugars  on  reduction,  or  the  dibasic  acids  on  oxidation 
with  nitric  acid. 

These  acids  may  be  separated  one  from  another  by  the  phenylhydrazine  reaction; 
all  of  them  have  the  same  constitution,  but  they  differ  in  the  spacial  arrangement  of  the 
groups  composing  the  molecule,  since  they  are  stereoisomerides  containing  various 
asymmetric  carbon  atoms  : 

OH  •  CH2  •  CH(OH)  •  CH(OH)  •  CH(OH)  •  CH(OH)  •  C02H, 

and  for  each  of  these  acids,  except  talonic,  the  dextro-  (d),  Isevo-  (I),  and  inactive  (i)  forms 
are  known. 

Some  of  these  stereoisomeric  forms  are  transformed  into  others  simply  by  the  action  of 
pyridine  and  a  little  water  (e.  g.,  d-mannonic  acid  gives  ^-gluconic  acid  and  vice  versa),  and 
the  inactive  forms  are  resolved  into  their  active  constituents  by  means  of  the  strychnine 
salts  (see  p.  23). 

The  HEPTONIC  ACIDS  are  also  derived  from  the  corresponding  sugars,  the  heptoses 
(see  later),  e.  g.,  rhamnohexonic  acid,  C6Hg(OH)5  •  C02H,  from  rhamnose ;  glucoheptonic  acid, 
C6H7(OH)6  -  C02H,  etc. 

D.   MONOBASIC   ALDEHYDIC    ACIDS 
(and  Aldehydic  Alcohols  and  Dialdehydes) 

GLYOXYLIC  or  ETHANOLOIC  ACID,  CO2H  •  CHO  -f  H2O,  gives  up  the  molecule 
of  water  with  which  it  is  combined  without  decomposing,  and  may  be  regarded  as  having 
a  structure  similar  to  that  of  chloral  hydrate,  CO2H  •  CH(OH)2;  the  salts  also  correspond 
with  this  formula,  although  they  retain  the  aldehydic  character.  It  occurs  widespread 
in  nature  in  sour  fruit  (gooseberries,  etc.),  and  is  obtained  synthetically  by  heating 
dibromoacetic  acid,  C02H  •  CHBr2,  with  water,  by  reducing  oxalic  acid  electrolytically, 
or  by  oxidising  ethyl  alcohol  with  nitric  acid.  It  crystallises  with  difficulty,  dissolves  in 
water  and  distils  in  steam. 

FORMYL ACETIC  ACID  (Semi-aldehyde  of  Malonic  Acid),  CO2H  •  CH2  •  CHO,  is 
obtained  as  acetal  from  the  acetal  of  acrolein.  The  isomeric  /3-hydroxyacrylic  acid 
(hydroxymethyleneacetic  acid),  CO2H  •  CH  :  CH  •  OH,  is  also  known,  and  is  obtained  as  ester 
by  a  synthesis  similar  to  that  of  ethyl  acetoacetate  (see  p.  369).  It  condenses  readily 
to  trimesic  acid,  C6H3(C02H)3. 

GLYCURONIC  ACID,  CO2H  •  [CH(OH)]4-  CHO,  is  obtained  by  reducing  saccharic 
acid,  and,  as  lactone,  melts  at  175°. 

GLYCOLLIC  ALDEHYDE  (Ethanolal),  OH  •  CH2  •  CHO,  is  obtained  by  the  action  of 
baryta  water  on  bromoacetaldehyde  in  the  cold.  It  is  known  only  in  aqueous  solution  and 
may  be  regarded  as  the  simplest  member  of  the  sugar  group,  of  which  it  gives  all  the 
reactions ;  it  reduces  Fehling's  solution,  even  in  the  cold.  When  oxidised  with  bromine 
water  it  gives  glycollic  acid,  whilst  in  presence  of  dilute  alkali  it  condenses,  forming  tetrose. 
If  heated  in  a  vacuum,  it  condenses  to  a  syrup,  which  retains  the  reducing  character.  With 
phenylhydrazine  acetate  it  yields  glyoxal  phenylosazone. 

GLYCERALDEHYDE,  OH  •  CH2  •  CH(OH)  •  CHO,  is  obtained  together  with  dihy- 
droxyacetone  (as  glycerose)  by  oxidising  lead  glycerate  with  bromine,  or  by  hydrolysis 
of  its  acetal.  On  condensation,  it  gives  acrose. 

ALDOL,  CH3  •  CH(OH)  •  CH2  •  CHO  (see  p.  245),  which  belongs  to  this  group  of  com- 
pounds, forms  a  dense  oil  soluble  in  water. 

GLYOXAL  (Ethandial),  CHO  •  CHO,  is  the  dialdehyde  of  glycol,  and  hence  combines 
with  2  mols.  of  bisulphite  [C2H2O2(S03HNa)2  +  H20]  or  hydrocyanic  acid.  It  is  formed, 
together  with  glycollic  acid,  by  gentle  oxidation  of  acetaldehyde  with  nitric  acid.  It  forms 
a  white  mass  which  is  soluble  in  alcohol  or  ether  and  absorbs  water  with  avidity.  Even 
in  the  cold,  alkalis  transform  it  into  glycollic  acid,  CHO  •  CHO  +  H2O  =  OH  •  CH2  •  C02H. 

CH  •  NHv  ,NH  •  CH 

With  concentrated  ammonia,  it  gives  glycosine,  \\  ^C-C^  ||     ,  which  is  con- 

CH  — N^         XN  — CH 

CH  •  NHv 

verted  to  a  large  extent  into  glyoxaline  (iminazole),  \\  ^^^. 

CH  —  W 


ORGANIC    CHEMISTRY 

E.    MONOBASIC    KETONIC    ACIDS 
(and  Keto-alcohols,  Diketones  and  Keto -aldehydes) 

Ketonic  acids  show  all  the  general  reactions  of  acids — i.  e.,  of  the  carboxyl 
group  (p.  321 ) — and  of  ketones — i.  e.,  of  the  carbonyl  group,  CO  (p.  243).  Their 
constitution  may  be  deduced  from  the  various  syntheses  and  from  the  known 
constitution  of  the  hydroxy-acids  derived  from  them  on  reduction. 

Interesting  behaviour  is  shown  by  the  esters  of  the  /3-ketonic  acids,  which, 
owing  to  the  mobility  of  a  hydrogen  atom  adjacent  to  the  carbonyl,  reacts 
sometimes  in  the  ketonic  form  and  sometimes  in  the  isomeric  enolic  form, 
which  represents  an  unsaturated,  tertiary  alcohol  : 

CH3  •  CO  •  CH2  •  C02C2H5^=zt  CH3  •  C(OH)  :  CH  •  C02C2H5. 

Ethyl  acetoacetate  (keto-form)  Ethyl  hydroxycrotonate  (enol-form) 

The  enolic  form  is  stable  only  as  derivatives,  e.  g.,  the  acetyl-derivatives, 
CH3  '  C(O  '  CO  '  CH3)  :  CH  •  C02C2H5,  these  derivatives  being  the  more  stable 
the  more  negative  the  residues  introduced  in  the  direction  of  the  carboxyl. 

This  phenomenon  is  tautomerism  or  pseudoisomerism  (see  p.  18). 

If  the  cc-carbon  atom,  adjacent  to  the  carbonyl,  has  one  of  its  hydrogen 
atoms  replaced  by  an  alkyl  group,  thus,  CH3  •  CO  •  CHE,  •  C02C2H5,  the  pheno- 
menon of  tautomerism  is  still  observed,  but  this  ceases  to  be  the  case  when 
both  these  hydrogen  atoms  are  replaced,  as  in  CH3  •  CO  '  CR2  '  C02C2H5.  The 
mobile  hydrogen  causing  the  tautomerism  is  solely  that  situate  between  two 
carbonyls  (1:3  diketones)  : 

-CO  —  CH2  —  CO  —  ±r^_C(OH):  CH'CO- 

so  that  such  behaviour  is  not  shown  by  acetylf ormic  acid,  CH3  •  CO  'CO2H ; 
diacetyl,  CH3  •  CO  •  CO  •  CH3 ;  acetonylacetone,CH3  •  CO  •  CH2  •  CH2  •  CO  •  CH3 ; 
levulinic  acid,  CH3  •  CO  •  CH2  •  CH2  •  C02H,  etc. 

The  tautomeric  forms  may  be  distinguished  and  are  stable  in  the  crystalline 
state,  even  near  the  melting-point ;  the  reciprocal  transformation  is  continuous 
and  very  rapid  in  either  the  fused  or  dissolved  state,  the  two  forms  finally 
attaining  proportions  varying  with  the  conditions  (especially  temperature 
and  nature  of  solvent). '  If  separation  of  the  two  forms  by  means  of  a  reagent 
is  attempted,  the  equilibrium  is  displaced  and  the  second  tautomeric  form 
is  transformed  into  the  one  which  has  reacted,  so  that  the  mixture  behaves 
as  a  single  substance,  unless  two  reagents  are  used  which  act  with  equal 
velocities  on  the  two  forms  giving  different,  separable  compounds ;  syntheses 
with  ethyl  chlorocarbonate  appear  to  correspond  with  these  conditions,  which 
are,  however,  not  easy  to  obtain.1 

1  Knorr  and  Kurt  Meyer  (1911)  have  succeeded  in  separating  the  two  components  of  a 
tautomeric  mixture  by  cooling  to  a  very  low  temperature  a  solution  of  the  mixture  in  a  suitable 
solvent  (e.  g.,  at  —  78°  the  concentrated  alcoholic  solution  of  ethyl  acetoacetate  deposits  crystals 
of  the  true  ketonic  form,  whereas  the  enolic  isomeride,  i.  e.,  ethyl  hydroxycrotonate,  CH3  •  C(OH ) : 
CH  •  C02C2H5,  remains  in  solution).  Another  method  of  separation  consists  in  cooling  to  —  78° 
a  suspension  of  ethyl  sodioacetoacetate  in  methyl  ether,  adding  insufficient  HC1  to  combine 
with  the  sodium,  filtering  the  undissolved  sodium  salt  and  rapidly  evaporating  the  solution 
in  a  vacuum  at  —78°;  the  hydroxycrotonic  ester  remains  free  from  the  ketonic  compound. 
The  two  pure  isomerides  thus  separated  may  be  mixed  in  different  proportions,  and  comparison 
of  the  molecular  refractions  (see  p.  18)  with  that  of  the  ordinary  ethyl  acetoacetate  shows  that  the 
latter  represents  a  dynamic  equilibrium  between  98  per  cent,  of  the  ketonic  and  2  per  cent, 
of  the  enolic  forms.  With  this  system  it  is  possible  to  follow  the  velocity  of  transformation 
or  the  displacement  of  the  equilibrium  by  the  action  of  a  catalyst  or  of  heat.  An  analogous 
method  serves  to  resolve  tautomeric  or  pseudomeric  mixtures  (see  p.  18)  of  acetyldibenzoyl- 
methane,  CH3  •  CO  •  CH(CO  •  C6H5)2,  tribenzoylmethane,  CH(CO  •  C6H5)3,  ethyl  diacetyl- 
succinate,  C2H5  •  C02  •  CH(CO  •  CH3)  •  CH(CO  •  CH3)  •  C02C2H5,  and  methyl  benzoylacetate, 
C6H5  •  CO  •  CH2  •  COjCHj. 

On  the  other  hand,  Kurt  Meyer  has  determined  accurately  the  percentage  of  enolic  com- 
pound present  in  the  tautomeric  mixture  by  titration  with  bromine,  since  in  solution  at  0°  the 
double  linking  of  the  enolic  form  fixes  two  atoms  of  bromine  in  a  few  seconds,  the  almost  pure 


KETONIC    ACIDS  395 

When  separated,  the  two  forms  may  be  readily  distinguished,  since  the 
enol  gives  an  intense  coloration  with  ferric  chloride,  with  which  the  ketone 
does  not  react.  After  some  days,  however,  the  coloration  yielded  by  the  former 
becomes  paler,  while  a  colour  also  appears  in  the  mixture  of  ketone  and  ferric 
chloride,  a  condition  of  equilibrium  between  the  two  forms  being  slowly  arrived 
at  in  each  case.  Sometimes  the  enolic  form  remains  unchanged  for  a  long  time 
in  chloroform  solution,  although  when  dissolved  in  alcohol  it  is  transformed 
more  or  less  completely  into  the  ketonic  form  in  the  course  of  a  few  days. 

The  enolic  form  —  which  is  soluble  in  alkali,  whereas  the  ketone  is  insoluble 
—  gives  (like  all  compounds  containing  a  double  bond]  a  greater  dispersion  and 
refraction  of  light,  and  also  a  greater  electromagnetic  rotation  of  the  plane  of 
polarisation^  than  the  corresponding  isomerides  without  double  bonds. 

METHODS  OF  PREPARATION.  Ketonic  acids  are  formed  by  gentle 
oxidation  of  secondary  hydroxy-acids  ;  thus,  lactic  acid  gives  pyruvic  acid, 
CH3  •  CH(OH)  •  C02H  +  O  =  H20  +  CH3  •  CO  •  CO2H. 

The  a-ketonic  acids  are  usually  obtained  by  hydrolysing  the  nitriles,  this 
reaction  indicating  the  constitution  : 

CH3  •  CO  •  CN  +  2H20  =  NH3  +  CH3  •  CO  •  C02H. 

Acetyl  cyanide  Pyruvic  acid 

/3-Ketonic  acids  are  obtained  as  esters  by  the  action  of  sodium  or  sodium 
ethoxide  on  ethyl  acetate  or  its  homologues  (see  the  Ethyl  Malonate  Synthesis, 
p.  369),  thus: 

/ONa 
CH3  •  CO2C2H5  +  C2H5  •  ONa  =  CH3  •  C^OC2H5 

Ethyl  acetate  Sodium  ethoxide  OCoHr 

"       • 


CH3  *  CV~OC2Hg  -\-  CH 
XOC2H5 


2C2H5  •  OH  +  CH3  •  C(ONa)  :  CH  •  CO2C2H5. 

Ethyl  sodioacetoacetate 

Acetic  acid  then  readily  expels  the  sodium  and  liberates  ethyl  acetoacetate, 
which  has  not  the  enolic  but  the  ketonic  constitution,  CH3  •  CO  •  CH2  •  C02C2H5. 
The  total  reaction  is  hence  as  follows  : 

CH3  •  CO2C2H5  +  CH3  •  C02C2H5  =  C2H5  •  OH  +  CH3  •  CO  •  CH2  •  CO2C2H5. 

Similarly  diketones  are  obtained  by  the  interaction  of  ethyl  acetate  and 
simple  ketones  in  presence  of  sodium  ethoxide  : 

CH3  •  C02C2H5  +  CH3  •  CO  •  CH3  ==  C2H5  •  OH  +  CH3  •  CO  •  CH2  •  CO  •  CH3. 

This  ethyl  acetate  synthesis  has  been  largely  used  to  prepare  compounds 
of  most  varied  characters.     Ethyl    formate  acts  similarly,   giving  hydroxy- 

ketonic  form  being  then  extractable  by  means  of  hexane  or  petroleum  ether  (in  this  way  ethyl 

OH 


acetoacetate  of  98-5  per  cent,  purity  is  extracted).     By  this  means  anthranol,  \  \,  may 

/\/\/\ 
be  separated  and  distinguished  from  anihrone,  \  \  (see  Aromatic  series ). 


1  Polarised  light  passes  unchanged  through  a  tube  containing  an  inactive  liquid,  but  if 
the  tube  is  surrounded  by  a  wire  through  which  an  electric  current  passes,  the  plane  of  polarisa- 
tion is  deviated,  and,  under  equal  conditions  of  temperature  and  current,  the  deviation  is  greater 
for  a  compound  with  a  double  bond  than  for  the  isomeride  without  such  a  bond. 


396  ORGANIC    CHEMISTRY 

methylene  derivatives  [containing  the  group  — C(OH)  =  ],  which  are  isomeric 
with  the  keto -aldehydes  : 

CH3  •  CO  •  CH3  +  H  •  C02C2H5  =  C2H5  •  OH  +  OH  •  CH  :  CH  •  CO  •  CH3. 

Acetone  Ethyl  formate  Hydroxymethyleneacetone 

y-Ketonic  acids  are  obtained  by  the  ketonic  decomposition  (see  later)  of 
the  products  of  reaction  of  ethyl  sodioacetoacetate  with  esters  of  a-halogenated 
acids  : 

CH3  •  CO  •  CHNa  •  C02C2H5  +  R  •  CHI  •  C02C2H5  = 

Nal  +  CH3  •  CO  •  CH<£™  ^Cft ^     +  H20 > 

CO2  -f  C2HS  •  OH  +  CH32-  CO5-  CH2  •  CHR  •  C02C2H5. 

y        f 

Properties  of  Ketonic  Acids.  While  the  a-  and  y-ketonic  acids  are  stable, 
the  /3-acids  readily  lose  CO2,  giving  the  corresponding  ketones.  Reduction 
of  y-ketonic  acids  yields,  not  hydroxy-acids,  but  y-lactones. 

As  we  saw  was  the  case  with  malonic  acid  (see  p.  369),  the  esters  of  ft- 
ketonic  acids  contain  a  hydrogen  atom  readily  replaceable  by  metals,  e.  g., 
ethyl  sodioacetoacetate,  CH3  •  CO  •  CHNa  •  CO2C2H5. 

Further,  ketonic  acids  readily  form  condensation  products;  with  aniline 
they  give  quinolines;  with  phenylhydrazine,  pyrazoles,  etc. 

PYRUVIC  ACID,  CH3  •  CO  •  C02H,  is  obtained  by  the  dry  distillation  of 
tartaric  or  racemic  acid,  an  intermediate  product  in  the  reaction  being  possibly 
glyceric  acid  (formed  by  loss  of  C02),  which  then  loses  water  and  yields  pyruvic 
acid.  It  is  formed  also  by  oxidising  lactic  acid  with  permanganate  or  by 
hydrolysing  acetyl  cyanide.  Pyruvic  acid  is  a  liquid  with  an  odour  of  acetic 
acid  and  of  meat-extract,  and  is  soluble  in  water,  alcohol,  or  ether.  It  boils 
at  165°  and  solidifies  at  9°.  It  is  a  more  energetic  acid  than  propionic  owing 
to  the  presence  of  a  carbonyl  group  in  close  proximity  to  the  carboxyl.  Its 
constitution  is  indicated  by  the  fact  that  with  nascent  hydrogen  it  gives 
ethylidenelactic  acid.  It  readily  forms  condensation  products  (e.  g.,  benzenes ; 
and  with  ammonia,  pyridine  compounds).  When  heated  at  150°  with  dilute 
sulphuric  acid,  it  loses  C02,  forming  acetaldehyde.  Electrolysis  of  a  con- 
centrated solution  of  potassium  pyruvate  results  in  the  union  of  the  anion 
of  the  acid,  CH3  *  CO  •  COO'  with  the  ion  OH',  cyanogen  and  acetic  acid  being 
formed ;  at  the  same  time  two  anions  combine  with  loss  of  2C02  and  formation 
of  diacetyl,  CH3  •  CO  '  CO  •  CH3.  This  represents  the  general  behaviour  of 
potassium  salts  of  ketonic  acids  on  hydrolysis. 

Of  interest  is  its  conversion  into  ethyl  alcohol  and  also  into  acetaldehyde 
and  C02  by  enzyme  action  (see  Note,  p.  136). 

Of  the  derivatives,  cysteine  (a-amino-/?-thiolactic  acid),  SH  •  CH2  •  CH(NH2)' 
C02H,  and  cystine,  the  corresponding  disulphide,  may  be  mentioned. 

a-Ketobutyric  acid,  CH3  •  CH2  •  CO  •  C02H,  has  no  special  importance. 

ACETOACETIC  ACID  (^-Ketobutyric  acid),  CH3  •  CO  •  CH2  •  CO2H,  is 
obtained  in  the  free  state  by  cautious  hydrolysis  of  its  ester,  and  forms  an 
extremely  acid  liquid  soluble  in  water,  in  which  it  gives  a  red  coloration  with 
ferric  chloride ;  when  heated,  it  readily  loses  C02  with  production  of  acetone. 

ETHYL  ACETOACETATE,  CH3  •  CO  •  CH2  •  C02C2H5,  is  of  far  greater 
importance  than  the  free  acid,  owing  to  the  very  varied  syntheses  in  which 
it  finds  application.  This  ester  is  obtained  in  the  form  of  its  crystalline 
sodium  derivative  by  the  action  of  sodium  and  alcohol  (sodium  ethoxide) 
on  ethyl  acetate  (see  above). 

Ethyl  acetoacetate  (freed  from  sodium  by  means  of  acetic  acid)  is  a  liquid 
having  a  pleasant,  fruity  odour,  and  dissolves  readily  in  alcohol  or  ether  and 
slightly  in  water,  in  which  it  gives  a  red  coloration  with  ferric  chloride.  It 


ETHYL    ACETOACETATE  397 

has  a  neutral  reaction  and  the  sp.  gr.  T030 ;  it  boils  at  181°  and  is  found  in 
diabetic  urine.  When  boiled  with  dilute  alkali  or  dilute  sulphuric  acid,  it 
undergoes  ketonic  decomposition,  forming  C02,  acetone  and  alcohol : 

CH3  •  CO  •  CH2  •  CO2C2H5  +  H20  =  CO2  +  C2H5  •  OH  +  CH3  •  CO  •  CH3. 

With  concentrated  alcoholic  potassium  hydroxide,  it  undergoes  acid 
decomposition,  producing  2  mols.  of  acetic  acid  : 

CH3  •  CO  •  CH2  •  C02C2H5  +  2H20  =  C2H5  •  OH  -f  2CH3  •  CO2H. 

Its  great  reactivity  is  due  to  the  readiness  with  which  one  of  the  hydrogen 
atoms  is  replaceable  by  metals  (Ba,  Al,  Zn,  Ag,  Cu,  etc.,  in  ammoniacal  solu- 
tion), especially  by  sodium.  Ethyl  sodioacetoacetate,  CH3  •  CO  •  CHNa  •  C02C2H5, 
is  a  white  solid  soluble  in  water,  while  ethyl  acetoacetate  is  soluble  in  alkali, 
from  which  it  is  reprecipitated  by  acids.  The  sodium  is  readily  replaced  by 
different  alkyl  groups  by  the  action  of  the  corresponding  alkyl  iodides  (see 
the  analogous  syntheses  with  Ethyl  Malonate,  p.  369).  Since  the  compounds 
thus  obtained  can  be  subjected  to  either  acid  or  ketonic  decomposition,  it  will 
readily  be  seen  how  very  varied  acids  and  ketones  may  be  obtained  by  means 
of  ethyl  acetoacetate.  For  instance,  the  action  of  normal  octyl  iodide  on 
ethyl  sodioacetoacetate  yields  methyl  nonyl  Tcetone,  a  constituent  of  oil  of  rue  : 

CH3  •  CO  •  CHNa  •  C02C2H5  +  CH2I  •  [CH2]6  •  CH3  = 

Nal  +  CH3  •  CO  •  OT<J9jyC'CH* 

t->u2u2±i5 

this  compound,  by  ketonic  decomposition,  giving  methyl  nonyl  ketone,  which 
must  hence  have  the  normal  structure,  CH3  *  CO  •  CH2  *  [CH2]7  •  CH3. 

Further,  by  eliminating  the  sodium  from  »thyl  sodioacetoacetate  by  means 
of  iodine,  the  two  residues  combine,  forming  ethyl  diacetylsuccinate : 

2CH3  •  CO  •  CHNa  •  C02C2H5  +  Ia  =  2NaI  +  CH3  •  CO  •  CH  •  C02C2H5 

CH3  •  CO  •  CH  •  C02C2H5 

and  this  ester,  on  ketonic  decomposition  (boiling  with  20  per  cent,  potassium 
carbonate  solution),  reacts  with  2H2O  and  gives  2CO2,  2C2H5  •  OH  and  acetonyl- 
acetone,  CH3  •  CO  *  CH2  •  CH2  •  CO  •  CH3,  which  has  a  normal  carbon-atom  chain 

4321 

and  is  a  1  :  4  diketone. 

Ethyl  acetoacetate  also  combines  with  formaldehyde  (in  presence  of 
diethylamine),  with  acetone  and  with  ammonia;  with  aniline  it  gives  di- 
phenylcarbamide.  With  one  or  two  mols.  of  sulphuryl  chloride  it  gives  ethyl 
chloracetoacetate  (b.-pt.  194°,  sp.  gr.  1*19  at  14°)  or  ethyl  dichlor acetoacetate, 
CH3  •  CO  •  CC12  •  C02C2H5,  which  boils  at  206°  and  has  the  sp.  gr.  1*293  at  16°. 

LEVULINIC  ACID,  CH3  •  CO  •  CH2  •  CH2  •  CO2H,  is  obtained  synthetically  by  the  acid 
decomposition  of  the  product  of  reaction  of  ethyl  acetoacetate  and  ethyl  chloracetate. 
It  may  be  prepared  by  boiling  hexoses,  cane-sugar,  cellulose,  gum,  starch,  etc.,  with 
concentrated  hydrochloric  acid. 

It  melts  at  33°  and  boils  at  239°  with  slight  decomposition,  or  at  144°  under  12  mm. 
pressure. 

It  is  sometimes  used  in  the  printing  of  textiles. 

KETO-ALCOHOLS 

ACETONEALCOHOL  or  ACETYLCARBINOL  (Propanolone),  CH3  -  CO  •  CH2  •  OH, 
is  formed  by  heating  either  grape-sugar  with  fused  potassium  hydroxide  or  a  mono-halo- 
genated  acetone  with  barium  carbonate.  It  is  a  liquid  which  boils  almost  unchanged  at 
147°  and  reduces  Fehling's  solution  even  in  the  cold. 


398  ORGANIC    CHEMISTRY 

DIHYDROXY  ACETONE  or  GLYCEROSE,  OH  •  CH2  •  CO  .  CH2  •  OH,  is  formed 
together  with  glyceraldehyde  by  oxidising  glycerol  with  nitric  acid.  It  has  a  sweet  taste 
and  may  indeed  be  regarded  as  a  triose  sugar.  It  crystallises  in  colourless  plates  and 
reduces  Fehling's  solution  in  the  cold. 

BUTAN-2-OL-3-ONE  (Dimethylacetol),  CH3  •  CO  •  CH(OH)  •  CH3,  also  reduces 
Fehling's  solution  and  is  obtained  by  reducing  diacetyl.  It  is  a  liquid  soluble  in  water 
and  boils  at  142°. 

The  higher  homologue,  acetoisopropyl  alcohol,  CH3  •  CO  •  CH2  •  CH  (OH  )  •  CH3,  b.-pt. 
177°,  is  also  known  and  is  formed  by  the  condensation  (by  means  of  alkali)  of  aldehyde 
with  acetone.  Removal  of  water  from  this  compound  yields  Ethylideneacetone, 
CH3  •  CO  •  CH  :  CH  •  CH3,  boiling  at  122°. 

DIKETONES 

All  diketones  give  mono-  and  di-oximes,  and  mono-  and  di-hydrazones,  the  latter  (as 
with  the  aldehydes)  bearing  the  name  of  osazones  and  being  usually  yellow.  They  often 
exhibit  tautomerism  and  give  rise  to  various  cyclic  condensation  products. 

DIACETYL  or  a-DIKETOBUTANE  (Butandione),  CH3  •  CO  •  CO  •  CH3,is  prepared  by 
the  general  method  for  diketones,  namely,  by  treating  methyl  ethyl  ketone,  CH3  •  CO  •  C2H5, 
with  amyl  nitrite  and  a  little  HC1,  the  CH2  group  being  transformed  into  —  C  :  NOH,  giving 
an  isonitrosoketone,  thus  : 

CH3  •  CO  •  CH2  •  CH3  +  N02  •  C5Hn  --  *    CH3  •  CO  •  C  •  CH3 

N-OH; 

when  boiled  with  dilute  sulphuric  acid,  this  compound  loses  the  hydroxyiminic  group  (as 
hydro  xylamine),  the  diketone  remaining. 

It  is  a  yellow  liquid  which  has  a  penetrating  odour,  dissolves  in  water  and  boils  at  88°, 
giving  yellowish-green  vapour  (sp.  gr.  0-973  at  20°).  With  hydrogen  peroxide,  diacetyl 
is  converted  quantitatively  into  2  mols.  of  acetic  acid  : 

CH3  •  CO  •  CO  •  CH3  +  H202  -  2CH3  •  C02H. 

CH3  •  C  :  N  •  OH 

DIMETHYLGLYOXIME  (Diacetyldioxime),  |  ,  forms  shining,  white 

CH3  •  C  :  N  •  OH 

crystals,  m.-pt.  234-5°,  insoluble  in  water,  but  soluble  in  alcohol  or  ether.  It  is 
obtained  by  shaking  50  grams  of  methyl  acetoacetate  in  the  cold  with  a  solution  of  30  grams 
of  NaOH  in  750  grams  of  water,  allowing  to  stand  for  twelve  hours,  and  adding  25  grams 
of  sodium  nitrite  and  a  little  methyl  orange;  to  the  mass,  cooled  with  ice,  30  per  cent. 
sulphuric  acid  is  gradually  added  until  the  yellow  coloration  changes  to  reddish.  Three 
hours  later  an  aqueous  solution  of  25  grams  of  hydroxylamine  hydrochloride  is  added, 
and  sufficient  soda  crystals  to  render  the  reaction  alkaline.  The  dimethylglyoxime  crystals 
separating  are  collected  on  a  suction-filter,  washed  with  water  and  dried  (yield  55  per  cent. 
of  the  ester  used). 

Dimethylglyoxime  is  the  most  sensitive  reagent  for  ferrous  salts,  but  is  now  used  more 
especially  for  the  quantitative  separation  of  nickel  from  cobalt,  since  in  neutral  or 
ammoniacal  solution  a  1  per  cent,  alcoholic  solution  of  the  oxime  precipitates  nickel,  but 
not  cobalt  or  other  metals. 

Prior  to  the  war  it  cost  £5  4s.  per  kilo. 

ACETYLACETONE,  CH3  •  CO  •  CH2  •  CO  •  CH3.  The  best  general  method  for  pre- 
paring 1  :  3-diketones  consists  in  treating  an  ester  with  sodium  ethoxide  : 

/ONa 

R  •  CO2C2H5  +  CaH5  •  ONa  =  R  •  C^  OC2H5  ; 

\OC2H5 

this  compound,  when  treated  with  a  ketone,  R'  •  CO  •  CH3,  loses  2  mols.  of  alcohol  and  yields 


R  •  C  ,  from  which  the  sodium  is  expelled  by  a  dilute  acid.     This  enolic  form, 

XCH  •  COR' 


MALIC    ACID  399 

,OH 

— C^  ,  readily  passes  into  the  ketonic  form,  —CO  —  CH2— ,  thus  giving  the 

XCH- 
compound  R  •  CO  •  CH2  •  CO  •  R'. 

Another  general  method  for  obtaining  1  :  3-diketones  consists  in  treating  the  sodium 
derivatives  of  acetylene  homologues  with  an  acid  chloride  and  then  acting  on  the  acetylenic 
product  with  sulphuric  acid,  so  that  it  combines  with  water : 

CH3  •  [CH2]4  •  C  i  CNa  +  CH3  •  CO  •  Cl  =  NaCl  +  CH3  •  [CH2]4  •  C  i  C  •  CO  •  CH3 ; 

Amylacetylene  Acetyl  chloride 

the  latter  +  H2O >  CH3  •  [CH2]4  •  CO  •  CH2  •  CO  •  CH3. 

As  in  ethyl  acetoacetate  and  ethyl  malonate,  the  two  hydrogen  atoms  of  the  methylene 
group  between  the  two  carbonyl  groups  are  here  also  replaceable  by  metals,  giving  volatile 
compounds  which  are  soluble  in  chloroform,  benzene,  etc.,  and  differ  from  true  salts,  their 
solutions  exhibiting  very  slight  electrical  conductivity. 

Acetylacetone  has  a  pleasant  odour  and  boils  at  137°.  When  boiled  with  water  it 
yields  acetone  and  acetic  acid. 

ACETONYLACETONE  (y-Diketohexane  or  Hexa-2  :  5-dione),  CH3  •  CO  •  CH2  -CH2  • 
CO  •  CH3,  is  obtained  by  ketonic  decomposition  of  the  product  of  interaction  of  ethyl 
acetoacetate  and  ethyl  chloracetate  (see  also  Levulinic  Acid);  it  boils  at  194°  and  has  an 
agreeable  smell. 

KETO-ALDEHYDES   AND   HYDROXYMETHYLENEKETONES 

PYRUVIC  ALDEHYDE  (Methylglyoxal  or  Propanolone),  CH3  •  CO  •  CHO,  is  a 
volatile  oil  obtained  by  decomposing  its  oxime  (isonitrosoacetone )  with  dilute  acid  (see 
Diacetyl ). 

ACETOACETALDEHYDE,  CH3  •  CO  •  CH2  •  CHO,  was  formerly  thought  to  have  been 
obtained  in  the  free  state,  but  more  exact  study  has  now  shown  the  compound  in  questioa 
to  be  the  unsaturated  isomeride,  HYDROXYMETHYLENEACETONE,  CH3  •  CO  •  CH  : 
CH  •  OH,  which  has  an  acid  character  and  is  obtained  by  the  interaction  of  acetone  and 
ethyl  formate  in  presence  of  sodium  ethoxide  (see  Ethyl  Acetoacetate).  It  boils  at  100° 
and  readily  condenses  into  1:3:  5-triacetyl benzene,  C6H3(CO  '  CH3)3. 

LEVULINALDEHYDE  (Pentanal-4-one),  CH3  •  CO  •  CH2  •  CH2  •  CHO,  boils  at  187°. 
It  is  obtained  as  a  decomposition  product  of  the  ozonide  of  rubber  (q.  v.). 

F.  POLYVALENT   DIBASIC   HYDROXY-ACIDS   AND   THEIR 
DERIVATIVES 

TARTRONIC  ACID  (Hydroxymalonic  or  Propanoldioic  Acid),  C02H  • 
CH(OH)  *  CO2H,  is  formed  by  the  spontaneous  decomposition  of  nitrotartaric 
acid  and  is  obtained  synthetically  by  oxidising  glycerol  with  potassium  per- 
manganate, by  eliminating  bromine  from  bromomalonic  acid  by  the  action  of 
moist  silver  oxide,  or  by  reducing  Mesoxalic  Acid,  CO(CO2H)2.  It  crystallises 
with  |H20  and  melts  at  184°,  losing  C02  and  forming  polyglycollides.  It  is 
soluble  in  water,  alcohol,  or  ether. 

MALIC  ACID  (Hydroxysuccinic  or  Butanoldioic  Acid),  C02H  •  CH(OH)  • 
CH2  •  CO2H,  occurs  in  abundance  in  unripe  fruits  (apples,  grapes,  quinces, 
and  sorb-apples,  from  which  it  is  extracted).  Its  crystals  melt  at  100°  and 
it  dissolves  in  wtiter  or  alcohol  and,  to  a  slight  extent,  in  ether.  When 
subjected  to  dry  distillation,  it  gives  fumaric  acid  and  maleic  anhydride. 
Synthetically  it  is  obtained  from  maleic  or  fumaric  acid  or  asparagine, 
and  also  by  the  action  of  moist  silver  oxide  on  bromosuccinic  acid,  and  by 
the  reduction  of  tartaric  acid  by  means  of  hydriodic  acid. 

As  it  contains  an  asymmetric  carbon  atom,  malic  acid  forms  three  optically 
different  stereoisomerides,  all  of  which  are  known.  Natural  malic  acid  is  laevo- 
rotatory,  that  derived  from  cZ-tartaric  acid  dextro-rotatory,  and  that  obtained 


400  ORGANIC    CHEMISTRY 

by  other  syntheses  inactive  but  resolvable  into  active  components  by  fractional 
crystallisation  of  the  cinchonine  salt. 

It  gives  an  acid  calcium  salt  readily  soluble,  and  a  normal  salt  slightly 
soluble  in  water.  The  presence  of  the  alcoholic  group  is  proved  by  the 
formation  of  acetylmalic  acid  (see  p.  224). 

For  the  amido-derivatives,  asparagine,  etc.,  see  later. 

Of  the  higher  homologues  of  malic  acid,  the  following  are  known :  Four 
isomeric  acids,  C3H5(OH)(C02H)2  (a-  and  fi-hydroxyglutaric  acids,  itamalic 
and  citramalic  acids);  diaterebinic  acid,  C5H9(OHJ(C02H)2,  which  readily 
forms  a  lactone,  and  terebinic  acid,  C7H10O4. 

TARTARIC   ACIDS,   C02H  •  CH(OH)  •  CH(OH)  •  C02H 

These  are  dibasic  and  tetravalent,  as  they  contain  two  secondary  alcoholic 
groups.  The  presence  of  two  asymmetric  carbon  atoms  leads  to  the  existence 
of  four  stereoisomerides,  which  have  already  been  considered  on  pp.  20-21  : 
(1)  ordinary  or  d-tartaric  acid;  (2)  Z-tartaric  acid;  (3)  racemic  or  para-  or 
di-tartaric  acid;  (4)  i-  or  meso-  or  anti-tartaric  acid. 

They  are  obtained  synthetically  from  dibromosuccinic  acid,  C02H  •  CHBr 
•  CHBr  *  C02H,  and  moist  silver  oxide,  from  glyoxal  cyanohydrin,  from 
glyoxylic  acid  by  reduction,  from  mannitol  by  oxidation  with  nitric  acid,  and 
from  f  umaric  or  maleic  acid  by  oxidation. 

(1)  d-TARTARIC  ACID.  This  is  the  ordinary  tartaric  acid,  which  occurs 
abundantly  as  such,  and  as  monopotassiuin  tartrate  (tartar)  in  many  fruits 
— especially  in  the  grape,  and  hence  in  wine,  from  which  it  is  extracted  in  a 
manner  to  be  described. 

Dextro-rotatory  tartaric  acid  forms  hemimorphic,  monoclinic  prisms  with 
a  decided  and  pleasant  acid  taste.  It  is  readily  soluble  in  water  or  alcohol 
and  almost  insoluble  in  ether.  One  hundred  parts  of  water  dissolve  114  parts 
of  the  acid  at  0°,  l25'7  at  10°,  139'4  at  20°,  156-2  at  30°,  176  at  40°,  195  at 
50°,  217-5  at  60°,  243'6  at  70°,  273'3  at  80°,  306'5  at  90°,  and  343'3  at  100°. 
The  acid  melts  at  170°,  giving  rise  to  various  anhydrides  and  to  pyruvic  and 
pyrotartaric  acids;  ultimately  it  carbonises  with  an  odour  of  burnt  bread 
or,  if  the  temperature  is  raised  considerably,  of  burnt  sugar. 

Energetic  oxidising  agents  convert  it  into  tartronic  acid  or  dihydroxy- 
tartaric  acid  and  finally  into  formic  acid,  carbon  dioxide,  etc.  In  the  hot, 
it  reduces  ammoniacal  silver  solutions  (see»*p.  413  for  a  sensitive  reaction  for 
tartaric  acid).  Certain  bacteria  transform  it  into  succinic  acid.  When 
burned,  tartaric  acid  and  tartrates  emit  an  odour  of  burnt  bread,  thus  differing 
from  citric  acid  and  citrates,  which  give  a  pungent  odour.  Even  in  the  hot, 
it  resists  the  action  of  sulphuric  acid  of  62°  Be. 

Owing  to  the  presence  of  alcoholic  groups,  tartaric  acid,  like  glycerol, 
hinders  the  precipitation  by  alkali  of  many  metallic  oxides,  e.  g.,  of  cupric 
oxide  in  Fehling's  solution  (containing  caustic  soda,  copper  sulphate,  and 
sodium  potassium  tartrate;  see  Sugar  Analysis),  the  intensely  blue,  soluble 

C02Na  •  CH  •  Ov 
compound,  /Cu,  being  formed;  this   compound  is   not  pre- 

C02K  •  CH  •  V 
cipitable  by  alkalis,  since  the  copper  no  longer  functions  as  cation,  but  is 

-  O  •  CO  •  CH  •  0, 
contained  in  the  anion,  /Cu,  which  migrates  to  the  positive 

—  O • CO • CH  •  V 
pole  or  anode  when  the  salt  is  electrolysed. 

Tartaric  acid  is  used  in  dyeing,  in  the  wine  industry,  in  the  preparation 
of  aerated  beverages  (lemonade),  in  medicine,  etc. 


TARTRATES  401 

The  following  salts  of  tartaric  acid  may  be  mentioned,  acid  potassium 
tartrate  being  considered  more  in  detail  later. 

ACID  POTASSIUM  TARTRATE  (Cream  of  Tartar),  CO2H  •  CH(OH)-  CH(OH)  • 
CO2K,  is  slightly  soluble  in  water  or  in  dilute  alcohol,  and  has  a  pleasant  acid  taste.  For 
its  commercial  preparation,  see  Tartar  Industry. 

NORMAL  POTASSIUM  TARTRATE,  C4H4O6H2  +  |H2O,  is  readily  soluble  in  water 
and  separates  from  highly  concentrated  solutions  in  monoclinic  prisms.  One  hundred  grams 
dissolves  in  75  grams  of  water  at  2°,  in  66  grams  at  14°,  in  63  grams  at  23°,  or  in  47  grams 
at  64°. 

SODIUM  POTASSIUM  TARTRATE  (Rochelle  Salt),  C4H4O6NaK  +  4H2O,  is  pre- 
pared by  neutralis.'ng  cream  of  tartar  solution  with  sodium  carbonate.  Copper  and  iron, 
present  as  impurities,  are  removed  by  means  of  hydrogen  sulphide,  the  solution  being  then 
heated  with  good  animal  charcoal,  filtered,  concentrated  and  allowed  to  crystallise;  the 
Rochelle  salt  separates  in  thick  columns  readily  soluble  in  water  and  slightly  so  in  alcohol. 
One  hundred  grams  of  the  crystallised  salt  dissolves  in  170  grams  of  water  at  6°.  It  is 
used  to  reduce  silver  salts  in  the  silvering  of  mirrors  and  also  for  medicinal  purposes  and 
to  prepare  Fehling's  solution.  It  costs  about  72s.  per  cwt. 

CALCIUM  TARTRATE,  C4H4O6Ca  +  4H2O,  occurs  ready  formed  in  the  grape  and 
in  senna  leaves.  The  crystallised  salt  (1  part)  dissolves  in  352  parts  of  boiling  water  or 
in  6265  parts  at  15°.  It  is  readily  soluble  in  cold  sodium  hydroxide  solution,  from  which 
it  separates  in  the  hot  as  a  white  jelly,  to  be  redissolved  on  cooling.  It  dissolves  in  acetic 
acid,  thus  differing  from  calcium  oxalate.  It  is  soluble  also  in  alkali  tartrates  and  in 
ammonium  salts.  The  crystalline  tartrate  loses  part  of  its  water  of  crystallisation  at  60°, 
15  p«  cent,  at  110°,  and  the  whole  at  130°. 

TARTAR  EMETIC  (or  Potassium  Antimonyl  Tartrate),  C4H406(SbO)K  +  |H2O,  is 
prepared  by  precipitating  SbOCl  from  a  solution  of  SbCl3  by  means  of  water,  boiling  the 
precipitate  with  soda  solution  and  dissolving  the  Sb2O3  thus  formed  in  a  solution  of  four 
or  five  times  its  weight  of  potassium  hydrogen  tartrate  in  50  parts  of  water.  After  filtra- 
tion and  concentration  the  solution  deposits,  on  cooling,  efflorescent,  trimetric  pyramids, 
which  are  soluble  in  water  (1  :  13  at  20°,  1  :  6  at  50°)  but  insoluble  in  alcohol.  At  100° 
it  loses  its  water  of  crystallisation  and  at  220°  the  double  molecule  loses  water  of  constitution 
and  gives  2KSbC4H206.  It  is  poisonous  and  is  used  in  medicine  as  an  emetic  and  in  dyeing 
cotton  as  a  mordant  for  basic  dyes  (price  about  £4  16s.  per  cwt.).  Germany  imported 
202  tons  in  1908  and  391  in  1909,  the  respective  exports  being  1030  and  1090  tons  in  the 
two  years. 

(2)  Z-TARTARIC  ACID  differs  from  the  d-acid  only  in  the  opposite  sign  of  its  rotation 
and  in  the  opposed  hemihedry  of  its  crystals.     Mixing  of  the  concentrated  aqueous  solu- 
tions of  the  two  acids  results  in  development  of  heat  and  the  formation  of  inactive  tartaric 
acid. 

(3)  RACEMIC  ACID  (Paratartaric  Acid),  (C4H606)2  +  2H2O,  represents  a  mixture  of 
dextro-  and  laevo-tartaric  acids  in  equal  proportions,  and  is  hence  optically  inactive  (see 
p.  21 ).     When  heated  alone  or,  better,  in  presence  of  concentrated  caustic  soda  solution, 
either  the  d-acid  or  the  meso-acid  (see  later)  is  transformed  into  racemic  acid.     The  latter 
is  obtained  from  the  mother-liquors  of  ordinary  d-tartaric  acid.     The  molecular  weight, 
determined  cryoscopically  or  from  the  vapour  densities  of  the  esters,  corresponds  with 
the  simple  molecule,  C4H6O6.     It  forms  triclinic  crystals  which  effloresce  in  the  air, 
and  is  less  soluble  than  the  active  acids.      From  sodium  ammonium  racemate  crystals, 
(C4H406)2Na2(NH4)2+ 2H2O;    Pasteur    separated    those    showing    dextro-    from    those 
showing  laevo-hemihedry,  thus  resolving  racemic  acid  into  its  optically  active  constituents. 
Only  in  the  crystalline  state  is  the  molecule  of  racemic  acid  regarded  as  double  that  of 
tartaric  acid,  whilst  in  dilute  aqueous  solution  it  is  assumed  to  be  decomposed  completely 
into  the  two  optical  antipodes. 

(4)  MESOTARTARIC  ACID,  C4H6O6  +  H2Or  is  optically  inactive  (p.  21)  and  is  not 
merely  a  mixture  of  the  active  compounds.     It  is  obtained  by  prolonged  boiling  of  d-tartaric 
acid  with  excess  of  caustic  soda.     Its  potassium  salt  is  more  soluble  in  water  than  those 
of  the  other  tartaric  acids. 

VOL.  ii.  26 


402  ORGANIC     CHEMISTRY 

THE   TARTAR   INDUSTRY 

MANUFACTURE  OF  POTASSIUM  BITARTRATE  (Cream  of  Tartar  or  Potassium 
Hydrogen  Tartrate).  Although  the  crude  prime  material  of  this  industry  is  very  abundant 
in  Italy  in  wine  residues,  it  is  only  within  the  last  few  years  that  the  working  has  been 
placed  on  a  rational  basis,  the  tartar  being  refined  and  tartaric  acid  prepared.  Although 
these  prime  materials  are  subject  to  an  export  duty  (10|(Z.  per  cwt. ),  the  exportation  from 
Italy  amounted  to  about  17,800  tons,  worth  £480,000,  in  1905,  and  17,850  tons,  worth 
£416,000,  in  1910.  The  treatment  of  these  products  requires,  besides  special  technical 
ability,  also  considerable  quantities  of  fuel,  and  to  this  are  partly  due  the  difficulties  of 
the  Italian  manufacturers. 

Cream  of  tartar  occurs  abundantly  in  the  green  extremities  of  vine-shoots  and  in  the 
grape,  and  part  of  it  remains  in  the  pressed  vinasse.  The  vinasse  of  southern  grapes  con- 
tains as  much  as  4  per  cent,  of  cream  of  tartar,  and  that  of  other  grapes  from  2  to  2-5  per 
cent.  Vinasse  that  has  not  been  in  contact  with  the  fermenting  must,  and  that  of  second 
wines  have  practically  no  commercial  value.1 

Another  portion  of  the  cream  of  tartar  which  remains  dissolved  in  the  must  gradually 
separates  (lees)  as  fermentation  proceeds — cream  of  tartar  being  less  soluble  in  alcoholic 
liquids  (wine) — and  finally  part  of  it  is  deposited  as  a  crystalline  crust  on  the  walls  of  the 
casks  during  the  winter,  the  solubility  being  less  in  the  cold. 

The  following  table  shows,  for  various  temperatures  :  I,  the  number  of  grams  of  cream 
of  tartar  dissolved  by  100  grams  of  water ;  II,  the  number  of  grams  dissolved  by  100  grams 
of  10  per  cent,  aqueous  alcohol  solution ;  and  III,  the  number  of  grams  contained  in  100  c.c. 
of  the  saturated  solution. 

0°  5°         10°  15°         20°  25°  30°  40°  50°         60°  70°  80°  90°  "lOO0 

I.      0-320  0-360  0-400"  0-470  0-570  0-680  0-900  1-31  1-81  2-40  3-20  4-50  5-70  C-90 

II.      0-141  0-175  0-212  0-253  0-305  0-372  0-460  0-570  0-710        — 

III.      0-370  —  0-376  0-411        —  0-843  1-020  1-450  1-931  2-475  3-160  4-050  —  5-850 

Alcoholic  potassium  acetate  solution  transforms  cream  of  tartar  partly  into  the  normal 
tartrate,  whilst  the  presence  of  free  acetic  acid  hinders  such  transformation. 

Tartaric  acid  causes  a  slight  diminution  in  the  solubility  of  tartar  in  wine,  whereas 
mineral  acids  increase  this  solubility. 

These  crude  products  are  of  different  colours  according  as  they  are  obtained  from  white 
wines  (white  tartar)  or  red  wines  (red  tartar),  and  according  to  the  degree  of  purity. 

Fresh  wine  lees  (forming  about  5  per  cent,  of  the  wine)  are  slimy,  of  a  dirty  red  colour, 
and  contain  yeasts,  colouring-matters,  cream  of  tartar  (10  to  25  per  cent.),  and  calcium 
tartrate  (6  to  20  per  cent. ).  Italian  wine  lees  are  the  richest  in  potassium  bitartrate  and 
the  poorest  in  calcium  tartrate.  When  removed  from  the  vats,  the  lees  are  placed  to 
drain  in  strong  bags  suspended  by  cords,  the  bags  being  afterwards  tied  up  and  pressed 
slightly  in  a  press.  They  are  then  removed  from  the  bags  and  dried  in  the  air,  being 
turned  from  time  to  time.  When  pressed  and  almost  dry,  they  contain  more  than  double 
as  much  tartar  as  when  in  the  fresh  state  (about  10  per  cent,  of  moisture,  6  to  10  per  cent. 
of  lime,  3  to  5  per  cent,  of  sarid,  25  to  40  per  cent,  of  tartaric  acid).  In  some  large  wineries 

1  One  quintal  of  grapes  yields  30  to  35  kilos  of  vinasse  and  65  to  70  of  must,  so  that  the 
annual  Italian  production  of  40,000,000  quintals  would  correspond  with  15  to  20  million  quintals 
of  vinasse,  containing,  on  the  average,  more  than  3  per  cent,  of  tartar,  i.  e.,  a  total  of  about 
700,000  quintals  (70,000  tons)  of  tartar.  The  vinasse  distilled  in  Italy  in  1909  amounted  to 
368,000  tons,  which  should  have  yielded  11,000  tons  of  cream  of  tartar,  but  this  was  largely 
lost.  The  tartar  is  estimated  by  the  method  of  Carles  :  a  kilo  of  the  vinasse  is  chopped  and 
mixed,  and  100  grams  weighed  and  boiled  for  ten  minutes  with  700  c.c.  of  water  in  a  litre  flask, 
the  liquid  being  subsequently  made  up  to  the  mark  with  distilled  water.  Five  hundred  cubic 
centimetres  of  the  filtered  solution  is  concentrated  to  about  ICO  c.c.,  70  c.c.  of  saturated  calcium 
acetate  solution  being  then  added  to  the  boiling  liquid;  after  mixing,  the  liquid  is  allowed  to 
cool  for  twelve  hours,  the  precipitated  calcium  tartrate  being  then  collected  on  a  tared  filter, 
washed  with  water,  dried  at  60°,  and  weighed.  Multiplication  of  the  result  by  2  and  deduction 
of  5  per  cent,  (to  allow  for  the  volume  occupied  by  the  vinasse  in  the  litre  flask)  gives  the  calcium 
tartrate  per  100  grams  of  vinasse;  further  multiplication  by  0-723  gives  the  corresponding 
amount  of  potassium  hydrogen  tartrate.  Ciapetti  has  rendered  this  method  more  exact  by 
transforming  the  calcium  tartrate  (by  potassium  bioxalate  in  the  hot)  into  potassium  hydrogen 
tartrate,  filtering  and  washing  the  residue,  concentrating  the  filtrate  and  adding  alcohol  to 
precipitate  the  potassium  bitartrate;  the  latter  is  washed,  redissolved  in  hot  water  and  titrated 
with  decinormal  caustic  soda  solution  (see  below,  Analysis  of  Tartar). 


TARTAR    INDUSTRY  403 

the  lees  are  passed  directly  to  the  filter-presses,  cakes  which  are  readily  dried  being  thus 
obtained. 

The  crude  tartar  contains  45  to  70  per  cent,  of  potassium  bitartrate  and  calcium  tartrate, 
and,  if  washed  and  crystallised  once  from  hot  water,  this  content  may  increase  to  75  to 
87  per  cent.,1  the  product  being  then  placed  on  the  market  under  the  name  of  crystals. 

As  a  rule  60  to  70  per  cent,  of  the  total  tartar  is  extracted  from  the  vinasse  after  the 
alcohol  has  been  distilled  off  with  steam  in  the  manner  indicated  on  p.  170.  The  forms  of 
apparatus  there  shown  give  almost  saturated,  boiling  solutions  of  tartar  (the  remaining 
vinasse  being  centrifuged  or  pressed  to  remove  all  the  tartaric  liquors),  which  are  allowed 
to  cool  in  shallow,  wooden  vessels.  In  these  vessels  are  hung,  after  some  time,  strings 

1  Analysis  of  Tartar.  Tartar  being  a  rather  expensive  substance  (£3  to  £4  per  cwt.),  it  is 
frequently  adulterated  with  sand,  gypsum,  etc.  It  is  always  bought  and  sold  on  its  strength, 
the  potassium  bitartrate  or  the  total  tartaric  acid  (thus  including  both  the  calcium  tartrate  and 
the  free  tartaric  acid)  being  determined. 

A  homogeneous  sample  is  finely  ground  and  sieved,  the  residue  being  again  ground. 

A  test  which  is  not  very  exact,  but  is  rapid  and  largely  used,  is  the  direct  titration  test.  The 
coarse  impurities,  sand,  clay,  sulphur,  woody  matter,  yeasts,  etc.,  are  estimated  by  boiling  a 
known  weight  of  the  crude  tartrate  with  water  acidified  with  HC1,  and  collecting,  washing,  drying, 
and  weighing  the  residue  on  a  tared  filter;  the  residue  is  sometimes  ashed. 

The  calcium  carbonate  is  determined  by  treating  with  an  acid  in  the  calcimeter  and  measuring 
the  carbon  dioxide  evolved,  and  the  total  lime,  including  that  of  the  tartrate,  by  calcining  a  given 
weight  of  the  tartar,  dissolving  out  the  potassium  carbonate,  treating  the  residual  calcium  car- 
bonate with  excess  of  standard  nitrous  acid  solution,  and  measuring  the  excess  of  the  acid  by 
titration  with  soda  solution.  The  total  lime  is,  however,  best  estimated  by  dissolving  2  grams 
in  HC1,  neutralising  with  ammonia,  precipitating  with  ammonium  oxalate,  and  heating  on  a 
water-bath,  the  precipitate  being  subsequently  collected  on  a  filter,  ignited  in  a  platinum  crucible 
and  weighed  as  CaO. 

The  titration  test  of  the  quantity  of  acid  potassium  tartrate  is  carried  out  by  dissolving  a  weighed 
amount  (2  to  3  grams)  of  the  tartar  in  water  and  titrating  the  boiling  solution  with  N/4-sodium 
hydroxide  solution,  using  very  sensitive  litmus  paper  as  indicator;  1  c.c.  of  N/4-caustic  "soda 
solution  corresponds  with  0-047  gram  of  potassium  bitartrate.  Multiplication  of  the  amount 
of  bitartrate  by  0-798  yields  the  corresponding  amount  of  tartaric  acid. 

For  international  trade,  the  potassium  bitartrate  is  nowadays  estimated  by  the  filtration 
process,  which  largely  excludes  errors  due  to  the  presence  of  tannin  substances  and  other  impurities 
which  also  react  with  litmus  : 

2-35  grams  of  the  substance  (crude  tartar,  sludge  or  lees )  are  heated  to  boiling  for  five  minutes 
with  400  c.c.  of  water  in  a  500  c.c.  flask;  water  is  again  added  and  the  whole  cooled,  made  up  to 
500  c.c.,  mixed  and  filtered  through  a  folded  filter.  Of  the  filtrate  250  c.c.  are  heated  to  boiling 
and  titrated  with  N/4-potassium  hydroxide  solution  (standardised  with  pure  bitartrate),  sensitive 
litmus  paper  being  used  as  indicator. 

For  more  exact  determinations,  Rammer's  recrystallisat!on  method  is  employed  : 

4-7025  grams  of  substance  (molecular  weight  of  tartar  divided  by  40)  are  heated  to  boiling 
with  30  to  40  c.c.  of  water  in  a  100  c.c.  flask,  the  solution  being  then  neutralised  with  N/4-caustic 
soda,  of  which  1  to  2  c.c.  in  excess  are  added.  The  volume  is  made  up  to  100  c.c.  and  of  the 
filtered  solution,  20  c.c.  are  rendered  decidedly  acid  with  acetic  acid  and  treated  with  100  c.c. 
of  a  mixture  of  alcohol  and  ether,  which  separates  the  potassium  bitartrate  completely  in  crystals. 
These  are  collected  on  a  filter,  washed  with  alcohol  and  ether,  rcdissolved  in  boiling  water,  and 
titrated  with  N/20-soda  solution. 

Determination  of  the  total  tartaric  acid.  This  gives  the  total  content  of  potassium  bitartrate, 
calcium  tartrate,  and  free  tartaric  acid.  The  Goldenberg-Geromont  hydrochloric  acid  process, 
which  was  formulated  as  follows  at  the  Congress  of  Applied  Chemistry  at  Turin  in  1902,  is  generally 
used  : 

Six  grams  of  the  substance  are  treated  for  eight  to  ten  minutes  in  a  small  beaker  with  9  c.c. 
(for  products  poor  in  tartar)  or  18  c.c.  (for  richer  products)  of  cold  HC1  (sp.  gr.  1-10),  the  whole 
being  then  washed  into  a  100  c.c.  flask,  made  up  to  volume,  mixed,  and  passed  through  a  dry 
pleated  filter.  Fifty  cubic  centimetres  of  the  filtrate  are  boiled  for  ten  to  fifteen  minutes  in  a 
tall  250  to  300  c.c.  beaker  with  5  (or  10)  c.c.  of  concentrated  potassium  carbonate  solution  (66 
grams  in  100  c.c.  of  water),  the  liquid  being  then  washed  into  a  100  c.c  flask,  cooled,  made  up 
to  volume,  and  filtered  through  a  pleated  filter.  Fifty  cubic  centimetres  of  this  filtrate  are  taken 
to  dryness  in  a  half -litre  dish,  redissolved  in  5  c.c.  of  boiling  water,  and  vigorously  stirred  with 
4  to  5  c.c.  of  glacial  acetic  acid ;  when  the  liquid  is  cold,  100  to  110  c.c.  of  96  per  cent,  alcohol 
are  mixed  in.  and  the  potassium  bitartrate  allowed  to  deposit.  This  is  filtered  under  pressure, 
the  dish,  rod,  and  filter  being  repeatedly  washed  with  alcohol.  The  filter  and  the  bitartrate  are 
then  washed  into  the  same  dish  with  boiling  water,  with  which  the  volume  is  made  up  to  about 
300  c.c.  The  liquid  is  then  boiled  and  titrated  with  N/4-alkali,  the  end -point  being  determined 
with  sensitive  litmus  paper. 

To  eliminate  the  error  due  to  the  volume  occupied  by  the  impurities  in  the  original  flask, 
0-7  per  cent,  is  deducted  from  the  total  content  in  the  case  of  low-grade  tartars  (containing 
less  than  20  per  cent,  of  bitartrate)  and  0-7  —  (n  X  0-02)  in  the  case  of  those  containing  20  to 
50  per  cent.,  n  being  the  excess  percentage  over  20 ;  beyond  50  per  cent,  the  correction  becomes 
almost  zero. 


404  ORGANIC     CHEMISTRY 

studded  with  tartar  crystals,  on  which  less  impure  crystals  gradually  form.  The  deposit 
forming  on  the  walls  of  the  vessels  is  of  a  leS3  degree  of  purity,  and  that  on  the  bottom 
contains  many  coloured  impurities.  In  five  to  six  days  the  crystallisation  is  complete, 
more  rapid  and  complete  separation  being  attained  in  very  cold  places  or  by  the  use  of 
artificial  cooling.  The  mother-liquors  decanted  from  the  tartar  may  be  utilised  again  for 
extraction  of  vinasse,  but  when  they  become  too  rich  in  impurities  or  mucilaginous  sub- 
stances, they  are  either  used  as  fertilisers,  since  they  contain  potassium  salts,  or,  better, 
are  treated  (Carles,  1910)  at  boiling  temperature  with  60  grams  of  potassium  ferrocyanide 
per  hectolitre,  the  iron,  alumina,  copper,  etc.,  present  being  thus  removed ;  the  clarified 
liquid  is  treated  with  lime  to  separate  calcium  tartrate,  the  potassium  salts  being  recoverable 
from  the  filtered  solution  by  the  Alberti  process  (see  later).1  The  dregs  deposited  during 
the  extraction  of  the  oream  of  tartar  from  the  vinasse  contain,  in  the  dry  state,  30  to  60 
per  cent,  of  potassium  bitartrate  and  10  to  20  per  cent,  of  calcium  tartrate. 

The  refining  of  crude  tartar  from  vinasse,  lees,  etc.,  is  very  difficult  with  the  poorer 
products,  and  in  practice  rich  and  poor  materials  are  often  mixed  so  as  to  give  a  content 
of  60  to  65  per  cent,  when  a  highly  refined  tartar  is  not  required. 

The  crude  tartar  or  other  mixture  should  first  be  ground  and  then  sieved  to  remove 
pieces  of  wood  and  other  impurities.  In  order  to  destroy  certain  impurities  and  protein 
substances  and  hence  hasten  the  filtration  of  the  subsequent  aqueous  solutions,  the  lees 
or  low-quality  tartar  is  treated  with  concentrated  sulphuric  acid  (60°  Be.)  or  heated  in 
revolving  iron  cylinders  until  the  temperature  reaches  160°  to  180°,  the  loss  in  weight  being 
8  to  12  per  cent,  (water  together  with  2  to  3  per  cent,  of  cream  of  tartar).  It  is  then  intro- 
duced into  a  perforated  copper  cylinder  placed  almost  on  the  bottom  of  a  large  wooden 
vessel  furnished  with  copper  or  aluminium  steam  coils.  Care  is  taken  not  to  use  an  excess 
of  water,  which  would  involve  waste  of  fuel,  and  generally  6  to  8  parts  of  water  are  taken 
per  1  part  of  tartar.  A  hood  is  usually  fitted  over  the  vessel  to  carry  off  the  steam  from 
the  boiling  solution.  In  order -to  transform  the  calcium  tartrate  present  into  potassium 
bitartrate,  3  kilos  of  hydrochloric  acid  (20  Be. ),  and  3  kilos  of  potassium  sulphate  (previously 
dissolved  in  20  litres  of  water)  are  added  to  the  water  per  kilo  of  lime  (CaO)  contained 
in  the  calcium  tartrate  (see  method  of  determination  given  above).  The  liquid  is  stirred 
occasionally,  boiled  for  an  hour  and  allowed  to  settle  for  about  a  further  hour,  after  which 
either  the  bitartrate  solution  is  decanted  by  means  of  a  tap  a  short  distance  from  the 
bottom,  or  the  whole  mass  is  passed  through  a  filter-press.  The  liquid  is  left  to  cool  in  a 
cold  place  in  ordinary  crystallising  vessels,  or,  better,  in  copper  or  aluminium  basins,  a 
somewhat  impure  and  reddish-brown  tartar  crystallising  out.  Rather  purer  tartar  may 
be  obtained  by  collecting  the  crystals  separating  while  the  solution  is  cooling  to  35°  or  40°, 
small  crystals  being  ensured  by  occasional  stirring ;  the  tepid  mother-liquors  are  then 
decanted  and  crystallised  in  a  cold  place. 

1  In  many  places  the  vinasse  is  placed  in  vats  fitted  with  false  bottoms,  steam  being  passed 
in  below  while  a  spray  of  mother-liquor  (red  liquors)  falls  from  above;  as  many  hectolitres  of 
these  liquors  are  employed  as  there  are  quintals  of  vinasse.  In  this  manner,  the  first  solution 
of  the  tartar  is  obtained  almost  boiling  and  almost  saturated ;  it  is  purified  by  percolating  slowly 
through  the  vinasse  (the  steam  expels  the  air  and  condenses ).  A  second  extraction  gives  a  less 
completely  saturated  solution,  which  is  utilised  for  further  extractions.  Finally,  the  vinasse  is 
not  pressed  but  is  washed  with  water  and  a  little  hydrochloric  acid  to  extract  the  calcium  tartrate, 
exhaustion  being  then  obtained  by  means  of  cold  water  (Tarulli's  method).  The  mother-liquors 
from  the  crystallisation,  when  they  become  too  impure  or,  in  some  cases,  even  after  the  first 
crystallisation,  are  treated  with  milk  of  lime  to  precipitate  all  the  dissolved  tartar,  while  the 
liquors  from  the  second  and  third  extractions  are  used  for  fresh  quantities  of  vinasse. 

To  obtain  purer  solutions  from  the  vinasse,  to  avoid  losses  occasioned  by  the  presence  of  lime 
in  the  water,  and  to  extract  calcium  tartrate  at  the  same  time,  Ciapetti  exhausts  the  vinasse 
with  dilute  solutions  of  sulphurous  and  hyclrosulphurous  acid — which  do  not  dissolve  the  colour- 
ing-matters or  the  pectic  or  albuminoid  substances — -and  allows  refined,  white  cream  of  tartar  (!) 
to  crystallise  out;  tho  mother-liquors  are  utilised  further.  This  method  was  tried  in  various 
works,  but  did  not  give  the  results  expected  of  it.  Extraction  on  the  Ciapetti  system  may  also 
be  carried  out  in  the  series  of  stills  used  for  the  distillation  of  the  vinasse  (see  later,  Tartaric 
Acid,  Gladysz  Process). 

The  fresh  vinasse  or  the  deposits,  if  not  to  be  worked  up  at  once,  may  be  kept  for  some  months 
if  tartaric  fermentation — which  would  destroy  part  of  the  cream  of  tartar — is  prevented,  either 
by  addition  of  0-05  per  cent,  of  sodium  thiosulphate  or  by  maintaining  the  vinasse  strongly 
compressed,  under  chalk  and  sand,  in  wooden  vats  (tartaric  fermentation  is  caused  principally 
by  Bacillus  saprogenes  vini).  The  yields  of  tartar  and  alcohol  are  determined  on  a  small  quantity 
(5  kilos)  of  the_ vinasse  in  a  small  Savalle  distilling  and  macerating  apparatus. 


405 

The  brown  mother-liquors  are  used  repeatedly  to.  dissolve  fresh  quantities  of  the  crude 
tartar  substances  in  the  hot.  The  brown  crystals  are  detached  from  the  crystallising 
vessels  by  means  of  suitable  spatulas  and  redissolved,  in  a  wooden  vessel  similar  to  that 
previously  used  (with  a  perforated  bottom  for  the  crystals),  in  ten  to  twelve  times  their 
weight  of  water,  which  is  boiled  by  indirect  steam  supplied  through  copper  or  aluminium 
coils.  Decolorisation  is  effected  by  adding,  after  half  an  hour's  boiling,  about  1  per  cent, 
of  animal  charcoal  (well  washed  with  hydrochloric  acid  and  thoroughly  rinsed ;  for  very 
impure  tartar  from  lees  as  much  as  6  to  8  per  cent,  of  animal  charcoal  is  used).  After 
mixing  and  an  hour's  boiling,  about  1  per  cent,  of  kaolin  free  from  chalk  (washed  with 
HC1)  is  well  mixed  in  in  the  hot  and  the  liquid  either  filter-pressed  or  left  for  two  to  three 
hours  so  that  the  kaolin  may  carry  down  all  the  suspended  charcoal.  In  some  cases  the 
solutions  are  clarified  by  adding  tannin  and  gelatine  (50  grams  of  the  latter  and  250  of 
tannin  dissolved  separately)  after  the  kaolin  and  before  filtration.  The  pale  yellow,  clear 
solution  is  decanted  (the  first  and  last  portions,  which  are  rather  turbid,  being  kept  separate) 
and  crystallised  in  wooden  crystallising  vessels  or  in  copper  or  aluminium  basins ;  in  three 
or  four  days  the  crystallisation  is  complete.  The  mother-liquors  are  used  to  dissolve  fresh 
brown  crystals,  since  they  contain  a  little  free  tartaric  acid  which  dissolves  many  of  the 
impurities  better  than  water  does,  and  so  results  in  the  separation  of  purer  crystals.  After 
the  removal  of  the  mother -liquor,  the  crystals  are  washed  repeatedly  with  very  pure  water 
(condensed),  a  trace  of  hydrochloric  acid  being  added  to  the  first  washing  water  if  the 
crystals  show  any  superficial  turbidity.  They  are  finally  dried  on  cloths  in  a  desiccator 
at  60°  with  the  help  of  a  current  of  air. 

In  France  and  also  in  certain  Italian  factories,  Carles  has  applied  a  method  of  extracting 
the  tartar  which  consists  in  treating  100  parts  of  the  crude,  powdered  tartar  with  400  parts 
of  water  at  70°,  containing  sufficient  sodium  carbonate  to  transform  all  tfce  potassium 
bitartrate  into  the  highly  soluble  sodium  potassium  tartrate  (1:1-2).  This  solution  is 
decanted  or  filtered  and  treated  with  more  than  the  amount  of  hydrochloric  or  sulphuric 
acid  necessary  to  neutralise  the  soda  added;  this  leads  again  to  the  formation  of  the 
slightly  soluble  potassium  bitartrate,  which  crystallises  out  (96  per  cent,  purity)  on  cooling. 
Vinasse  is  also  extracted  more  readily  by  this  alkaline  method. 

The  recent  process  of  Cantoni,  Chautems  and  Degrange  (1910)  refines  the  tartar  almost 
in  the  cold  and  effects  a  marked  economy  of  chemical  products.  This  method  serves  well 
also  for  poor  products  (20  per  cent,  lees),  which  are  heated  as  described  above  and  washed 
first  with  cold  sodium  carbonate  solution  in  a  series  of  vessels,  next  slightly  with  water, 
and  finally,  slowly  and  systematically  with  dilute  hydrochloric  acid. 

In  the  first  case,  sufficient  soda  is  added  to  convert  the  tartar  almost  completely  into 
sodium  potassium  tartrate,  which  is  highly  soluble  and  may  be  extracted  with  the  minimum 
quantity  of  water.  The  treatment  with  hydrochloric  acid  dissolves  the  remainder  of  the 
tartar  and  also  the  calcium  tartrate.  The  amount  of  the  acid  used  is  chosen  so  that,  when 
the  alkaline  and  acid  solutions  are  united,  it  neutralises  the  soda  first  used.  The  hydro- 
chloric acid  solution  is  mixed  previously  with  the  amount  of  oxalic  acid  required  to  preci- 
pitate the  whole  of  the  lime  present  in  the  crude  tartar  as  calcium  tartrate,  while  sufficient 
potassium  chloride  is  added  to  the  alkali  solution  to  transform  all  the  tartaric  acid,  existing 
as  calcium  tartrate,  into  potassium  bitartrate.  Mixing  of  the  two  solutions  in  the  cold 
results  in  the  precipitation  of  almost? all  the-cream  of  tartar  in  a  white,  highly  pure  state, 
and  of  the  calcium  oxalate.  After  filtering,  the  dark  mother-liquors  areTsept  for  subsequent 
operations,  while  the  solid  residue  is  treated  with  the  calculated  (on  the/solubility  of  the 
tartar)  quantity  of  water  at  90°,  a  little  oxalic  acid  being  added  to  render  the  calcium 
oxalate  less  soluble.  The  mass  is  then  filtered  or  centrifuged  (if  necessary,  decolorised 
with  a  small  amount  of  animal  charcoal),  the  clear  liquid,  on  cooling,  depositing  refined 
tartar  of  a  purity  of  99  to  99-5  per  cent.  The  mother-liquor  is  used  to  initiate  the  solution 
of  further  quantities  of  crude  tartar,  etc.  Oxalic  acid  may -be  recovered  from  the  calcium 
oxalate. 

A  process  which  allows  of  the  conversion  of  calcium  tartrate  into  potassium  bitartrate 
consists  in  boiling,  say,  100  kilos  of  the  calcium  tartrate  (85  per  cent.)  with  1500  litres  of 
water  and  53-5  kilos  of  potassium  bisulphate  (or  a  mixture  of  35  kilos  of  the  neutral  sulphate 
and  24-6  kilos  of  sulphuric  acid  at  60°  Be.)  for  half  an  hour,  decanting  and  filtering  the 
liquid,  from  which  pure  potassium  bitartrate  (up  to  98  per  ce'nt. )  crystallises  on  cooling. 

This  process  is  a  modification  of  that  of  Martignier  (Fr.  Pat.  Nov.  23,  1889),  who 


406 


ORGANIC     CHEMISTRY 


transforms  calcium  tartrate  into  normal  potassium  tartrate  by  decomposition  with  normal 
potassium  sulphate;  after  filtration  and  concentration  and  addition  of  the  calculated 
amount  of  sulphuric  acid,  the  solution  deposits  potassium  tartrate. 

If  the  cream  of  tartar  crystals  are  not  pure  but  contain  small  proportions  of  calcium 
tartrate,  they  do  not  give  perfectly  clear  solutions  in  water.  When  the  pale  mother-liquors 
from  the  final  refining  are  somewhat  impure,  they  are  used  in  place  of  the  brown  liquor  to 
dissolve  the  crude  material,  the  highly  impure  brown  liquors  being  used  in  the  manufacture 
of  tartaric  acid  or  added  in  small  amounts  to  the  prime  tartaric  materials. 

STATISTICS  AND  USES.  Italy  exported  and  imported  the  following  quantities  of 
tartar  materials  : 


Crude  tartar  and  cask  deposits 

Wine  lees 

Pure  cream  of  tartar 

Year 

Imported 

Exported 

Imported 

Exported 

Imported 

Exported 

Tons 

Value 

(*) 

Tons 

Value 

(£) 

Tons 

Value 
(«)' 

Tons 

Value 

(£) 

Tons 

Value 

(£) 

Tons 

Value 
(£) 

1906 

492 

17,701 

16,828 

605,824 

Includ 

edin  cru 

de  tarta 

r,  etc. 

35 

2,082 

19 

1,241 

1908 

106 

3,587 

10,405 

353,773 

231 

2,581 

8,311 

93,081 

66 

3,564 

16 

948 

1910 

275 

9,004 

10,278 

337,120 

161 

1,673 

7,574 

78,760 

63 

3,392 

32 

1,944 

1912 

172 

—  - 

8,594 

—  . 

156 

— 

6,169 

88,834 

119 

8,839 

— 

—  . 

1913 

273 

11,361 

8,505 

353,791 

456 

6,571 

4,054      58,376 

34 

2,491 

— 

.  — 

1914 

360 

18,694 

9,964 

518,107 

443 

6,766 

6,298      80,533 

332 

31,901 

600 

57,600 

1915 

1,412 

107,312 

7,897 

600,164 

564 

11,737 

2,391 

49,722 

105 

17,347 

1,456 

241,613 

1916 

541 

41,108 

4,670 

354,928 

2,076 

43,177 

40             836 

18 

2,921 

976 

161,933 

1917 

228 

25,047 

6,693 

776,400 

326 

13,048 

•111       17,632 

1 

286 

729 

189,592 

1918 

15 

1,617 

6,809 

789,867 

384 

15,344 

1,041       41,656 

•  —  • 

— 

605 

157,214 

The  exports  from  Italy  are  sent  mostly  to  France,  Great  Britain,  and  the  United  States. 

The  total  Italian  production  of  tartar,  etc.,  in  1905  has  been  estimated  at  £1,600,000, 
the  world' s  production  being  valued  at  about  £2,800,000  (probably  too  low).  Crude  tartar 
and  lees  pay  an  export  duty  from  Italy  of  Is.  Qd.  per  quintal,  no  import  duty  being  levied ; 
refined  tartar  pays  an  import  duty  of  3s.  2d.  Italy  contains  about  200  crude  cream  of  tartar 
works,  but  only  very  few  manufacturing  refined  tartar. 

Great  Britain  imported  (usually  one-half  from  France  and  one-fourth  from  Germany) 
3200  tons  of  cream  of  tartar  in  1918,  4000  in  1910,  3890  in  1912,  and  3980  in  1913. 

For  Germany  the  importation  (of  crude  tartar  and  calcium  tartrate)  and  exportation 
(of  pure  cream  of  tartar)  are  (tons) : 


Importation 
Exportation 


1908 

2691 
1225 


1909 

2026 
1154 


1910 

3067 
1783 


1912 

4258 
2199 


1913 

6310 
3353 


In  1910  France  produced  12,000  tons  of  crude  tartar  and  more  than  6000  tons  of  refined 
cream  of  tartar.     The  imports  and  exports  are  as  follows  (tons ) : 


Wine  residues 

(  imports 
\exports 

Crude  tartar 

(imports 
\exports 

Tartar  crystals, 
etc. 

f  imports 
\exports 

Refined  cream  of 
tartar 

f  imports 
\exports 

1913 

10,876 
1,992 

1,417 
9,415 

163 

16 

4,408 


1914 

8,561 
1,867 

1,140 
5,500 

26 

25 
3,499 


1915 

8,038 
932 

1,279 
4,973 

247 

48 
3,208 


1916 

5,575 
666 

887 
4,216 

26 

49 
2,268 


At  least  one-half  of  the  refined  cream  of  tartar  is  exported  to  Great  Britain. 

The  United  States  imported  14,000  tons  of  cream  of  tartar  in  1910,  13,800  in  1911, 
13,000  in  1912,  and  14,000  (£560,000)  in  1913. 

'  Before  1913  the  United  States  levied  an  ad  valorem  import  duty  of  5  per  cent,  for  low- 
grade  and  25  per  cent,  for  high-grade  cream  of  tartar.  After  1913  a  new  tariff  was  to 
come  into  force,  but  now  that  the  war  is  over  the  question  remains  unsettled — as  in  other 
countries  also. 


MANUFACTURE    OF    TARTAR  1C    ACID      407 

The  price  of  crude  and  refined  tartar  products  varies  widely,  even  in  one  and  the  same 
year,  according  to  the  requirements  of  the  markets  and  also  to  speculation  in  raw  materials 
and  refined  products. 

Before  the  war  crude  cream  of  tartar  was  sold  at  \\\d.  to  14£df.  or  even  less  per  unit 
or  kilo  of  the  pure  tartar  in  100  kilos  of  crude  product,  and  the  refined  at  Is.  Qd.  to  Is.  lid. 

During  and  since  the  war  the  price  of  the  crude  material  has  become  quadrupled  and 
that  of  the  refined  product  quintupled. 

Cream  of  tartar  is  largely  used  in  dyeing,  in  the  bichromate  mordanting  of  fast  wool 
dyes,  etc.,  and  in  the  printing  of  textiles.  Considerable  quantities  are  used  in  the  United 
States,  Australia,  Japan,  China  and  India  for  preparing  powder  which  is  added  to  dough 
to  render  the  bread  light  and  elastic ;  this  powder  contains  69  per  cent,  of  tartar  and  31 
per  cent,  of  sodium  bicarbonate.1 

MANUFACTURE  OF  TARTARIC  ACID.  This  acid  is  prepared  by  decomposing 
its  salts  (cream  of  tartar,  lees,  calcium  tartrate,  etc.),  the  dark  mother-liquors  and  the 
deposits  and  sludges  of  cream  of  tartar  factories  being  most  commonly  employed. 

Attempts  were  at  one  time  made  to  liberate  the  acid  from  its  soluble  salts  by  treating 
these,  in  hot  solutions,  with  hydrofluosilicic  acid,  which  separates  as  insoluble  potassium 
fluosilicate,  the  solution  of  tartaric  acid  remaining  being  filtered,  concentrated  and  crystal- 
lised. The  potassium  fluosilicate  is  treated  with  calcium  carbonate  to  convert  it  into 
soluble  potassium  carbonate  and  insoluble  calcium  fluosilicate,  which  yields  hydrofluosilicic 
acid  under  the  action  of  an  energetic  acid.  Tartaric  acid  has  also  been  prepared  by  treating 
solutions  of  its  salts  with  potassium  carbonate  and  then  with  barium  chloride,  the  latter 
precipitating  the  neutral  potassium  tartrate  partly  formed  by  the  former  reagent. 

At  the  present  time,  however,  the  method  most  commonly  used  consists  in  treating 
boiling  cream  of  tartar  solutions  with  milk  of  lime  or  powdered  calcium  carbonate.  In  this 
way  one-half  of  the  tartar  is  converted  into  insoluble  calcium  tartrate  and  the  other  half 
into  the  soluble  normal  potassium  tartrate,  the  latter  being  then  separated  as  the  insoluble 
calcium  salt  by  addition  of  calcium  sulphate  or  chloride  : 

2C4H506K  +  CaC03  =  H20  +  CO2  +  C4H4O6Ca  +  C4H4O6K2 ; 
C4H406K2  +  CaS04  =  K2SO4  +  C4H4O6Ca. 

The  acid  is  liberated  from  calcium  tartrate  by  means  of  sulphuric  acid  : 
C4H406Ca  +  H2S04  =  CaSO4  +  C4H6O6. 

According  to  the  nature  of  the  materials  employed,  various  procedures  are  adopted. 

Crude  tartar  is  freed  from  coarser  impurities  by  passing  through  a  wide-meshed  sieve, 
heated  if  necessary  (see,  above ),  ground  to  a  fine  granular  condition  and  placed  in  a  wooden 
vessel,  where  it  is  treated  with  eight  to  ten  times  its  weight  of  boiling  water.  The  mass 
is  well  mixed  with  a  stirrer  and  heated  to  boiling  by  a  steam  jet,  most  of  the  tartar  then 
dissolving.  A  paste  of  calcium  hydroxide  (sieved )  is  then  added  until  a  small  portion  of  the 
liquid  gives  only  slight  effervescence  with  calcium  carbonate  (as  a  rule,  160  grams  of  quick- 
lime, made  into  a  10  per  cent,  paste,  are  required  for  each  kilo  of  potassium  tartrate),  the 
mixture  being  then  boiled  for  fifteen  minutes. 

In  this  way  calcium  tartrate  is  precipitated,  while  normal  potassium  tartrate  remains 
in  solution.  The  latter  is  then  precipitated  as  calcium  salt  by  boiling  with  a  slight  excess 
of  gypsum  or  of  calcium  chloride  solution  (300  grams  of  the  chloride  per  kilo  of  tartrate 
used )  for  about  two  hours ;  a  little  precipitated  calcium  carbonate  is  finally  added  to 
precipitate  the  neutral  tartrate  as  completely  as  possible.  In  some  cases,  however,  the 
liquid  is  left  slightly  acid  to  prevent  separation  of  iron  and  aluminium  salts.  It  is,  indeed, 
necessary  to  ensure  the  absence  from  the  various  reagents  (lime,  chalk,  gypsum,  etc.) 
of  iron,  aluminium,  and  especially  magnesium,  the  latter  forming  magnesium  tartrate,  which 
is  ultimately  found  as  magnesium  sulphate  in  the  tartaric  acid  after  the  calcium  tartrate 

1  Cream  of  Tartar  in  Bread-making.  When  bread  is  made  with  yeast,  an  appreciable 
amount  of  sugar,  derived  from  the  flour,  is  lost  owing  to  its  conversion  into  alcohol  and  carbon 
dioxide.  The  yeast  may  be  replaced  by  500  grams  of  cream  of  tartar  and  225  grams  of  sodium 
bicarbonate  per  50  kilos  of  flour,  the  doughed  mixture  being  left  to  stand  until  evolution 
of  carbon  dioxide  commences ;  it  is  then  divided  into  loaves  and  baked,  good  light  bread  being 
thus  obtained.  Production  of  C02  by  means  of  bicarbonate  and  hydrochloric  acid  has  also  been 
proposed,  addition  of  salt  being  then  unnecessary.  Some  years  ago  Candia  suggested  the  use  of 
compressed  C02  for  this  purpose,  the  composition  of  the  dough  thus  remaining  quite  unchanged. 


408  ORGANIC     CHEMISTRY 

has  been  treated  with  sulphuric  acid.  The  boiling  liquid  is  kept  mixed  and  is  afterwards 
either  allowed  to  cool  to  40°  and  decanted  or  passed  immediately  to  the  filter-press ;  after 
repeated  washings  with  hot  and  cold  water,  the  crude,  dry  tartrate  is  placed  on  the  market 
and  the  nitrate  either  rejected  or  evaporated  to  obtain  the  potassium  chloride  present. 
Where,  however,  the  calcium  tartrate  is  converted  into  tartaric  acid,  it  is  not  necessary  to 
filter  and  dry  it,  the  tartrate,  after  the  first  decantation,  being  mixed  with  various  separate 
amounts  of  water,  which  are  drawn  off  when  the  precipitate  settles.  The  calcium  tartrate 
remaining  may  then  be  treated  in  the  same  vessel  with  sulphuric  acid  as  described  above. 

The  procedure  is  rather  more  complicated  in  the  case  of  wine  lees  (sediments,  sludge, 
etc. ),  as  the  tartrate  cannot  be  extracted  merely  by  treatment  with  water  and  filtration, 
owing  to  the  presence  of  considerable  amounts  of  mucilaginous  protein  substances  (fer- 
ments), which  impede  filtration,  so  that  they  are  either  treated  with  concentrated  sulphuric 
acid  (60°  Be.)  or  heated  (see  above).  The  moist  lees  (drained  in  bags  and  pressed)  contain 
as  much  as  8  per  cent,  of  cream  of  tartar,  or,  if  dried  in  the  sun,  still  more. 

These  lees  are  nowadays  worked  by  the  Dietrich  and  Schnitzer  process  (1865) :  they 
are  first  powdered  and  mixed  by  means  of  stirrers  and  then  heated  for  five  to  six  hours  in 
iron  autoclaves  (4  metres  high  and  1-4  wide  for  15  quintals  of  lees )  at  4  to  5  atmos.  pressure, 
direct  steam  being  admitted  by  copper  coils  and  the  air  first  allowed  to  escape.  The  albu- 
minoids are  thus  coagulated,  together  with  large  quantities  of  colouring-matters,  and  the 
mass  may  then  be  easily  filtered,  but  before  this,  it  is  discharged  into  a  lead-lined  wooden 
vessel  (holding  10  to  12  cu.  metres)  containing  3  cu.  metres  of  water  and  the  amount  of 
hydrochloric  acid  (20°  to  22°  Be. )  corresponding  with  the  quantity  of  tartar  previously 
determined  (100  kilos  of  potassium  bitartrate  require  60  kilos  of  hydrochloric  acid  at 
20°  Be.,  or  54-5  kilos  at  22°  Be. ).  The  mass  is  well  mixed  and  passed  through  the  filter- 
press,  in  which  it  is  washed  with  water.  The  tartaric  acid  is  then  separated  from  the 
solution  as  calcium  tartrate,  as  described  above. 

Lees  may  be  treated  economically  and  well  by  the  process  of  Cantoni,  Chautems,  and 
Degrange  described  above. 

To  utilise  the  potash  salts  of  the  filtrate  from  the  calcium  tartrate,  A.  Alberti  (U.S. 
Pat.  957,295,  1910)  decomposes  the  organic  substances  in  the  hot  with  calcium  chloride, 
filters  and  concentrates  in  a  vacuum. 

The  second  phase  of  the  manufacture  of  tartaric  acid  consists  in  the  decomposition  of 
the  calcium  tartrate  by  means  of  sulphuric  acid  (see  above)  and  in  the  subsequent 
crystallisation  of  the  tartaric  acid. 

The  calcium  salt  in  the  decantation  or  washing  vessels,  or  as  cakes  from  the  filter-presses, 
is  broken  up  and  suspended  in  five  to  six  times  its  weight  of  water  in  lead-lined  wooden 
vessels  furnished  with  stirrers  covered  with  lead  and  with  coils  for  indirect  steam-heating. 
After  the  liquid  paste  has  been  well  stirred,  the  sulphuric  acid,  previously  diluted,  is  added 
in  such  amount  that,  after  an  hour's  stirring  at  60°  to  70°,  there  is  still  a  slight  excess  of 
sulphuric  acid,  detectable  by  the  faint  green  coloration  imparted  to  a  solution  of  methyl 
violet.  Top  great  an  excess  of  sulphuric  acid  produces  blackening  of  the  tartaric  acid 
solution  during  concentration,  whilst  deficiency  of  sulphuric  acid  results  in  the  formation 
of  turbid,  impure  tartaric  acid  crystals ;  when  a  little  free  sulphuric  acid  is  present,  fine 
shining  crystals  are  obtained.  Usually  1  kilo  of  sulphuric  acid  at  66°  Be.  is  employed  per 
3  kilos  of  dry  calcium  tartrate.  The  solution  is  boiled  for  a  couple  of  hours,  left  to  cool, 
and  the  calcium  sulphate  which  forms  separated  by  means  of  a  filter-press,  washed  with 
a  little  tepid  water  (this  being  added  to  the  filtrate),  and  then  with  much  cold  water  (this 
being  used  for  treating  subsequent  quantities  of  calcium  tartrate).  The  tartaric  acid 
solutions  were  at  one  time  concentrated  in  shallow,  lead-lined,  wooden  vessels  containing 
leaden  steam-coils,  but  nowadays  concentration  is  carried  out  in  vacuum  pans  which 
are  similar  to  those  described  later  in  dealing  with  the  sugar  industry  and  are  of  hard 
lead  and  of  considerable  thickness. 

The  liquid  is  evaporated  until  it  becomes  almost  syrupy,  and  is  then  discharged  into 
wooden  vessels  containing  stirrers,  which  cool  the  concentrated  solution  rapidly  and  thus 
cause  the  tartaric  acid  to  separate  in  small  crystals.  The  cold  mass  is  quickly  separated 
from  the  mother-liquor  in  a  centrifuge,  the  crystals  being  washed  with  a  fine  spray  of  cold 
water.  The  mother-liquors  are  then  concentrated  until  they  give  crystals,  this  process 
being  carried  out  three  times ;  they  are  finally  treated  with  milk  of  lime  to  separate  the 
residual  tartaric  acid  as  calcium  tartrate,  which  is  filtered  and  worked  up  with  the  other 


TARTARIC    ACID    STATISTICS  409 

calcium  tartrate.  The  tartaric  acid  crystals  are  dissolved  in  one-half  their  weight  of 
boiling  water  (if  necessary,  the  solution  is  decolorised  with  animal  charcoal  and  filtered) 
and  the  liquid  left  to  crystallise,  the  crystals  thus  obtained  being  centrifuged  and  dried  on 
sheets  of  lead  in  a  current  of  air  at  30°;  the  mother-liquors  are  used  to  dissolve  fresh 
quantities  of  the  small  crystals. 

The  final  yield  is  about  90  to  95  per  cent,  of  the  total  tartaric  acid  in  the  prime  materials 
when  these  are  poor  (e.  g.,  lees  with  20  to  25  per  cent,  of  tartar)  or  97  to  99  per  cent,  when 
richer  prime  materials  (70  to  80  per  cent,  of  tartar)  are  used. 

A  process  still  little  used,  but  worked  successfully  for  many  years  in  the  Montredon 
factory  near  Marseilles,  is  that  of  Gladysz  (Ger.  Pat.  37,352,  October  15,  1885),  which  is 
based  on  the  following  observations  :  (1)  When  calcium  tartrate  is  suspended  in  water 
and  saturated  with  sulphur  dioxide,  soluble  calcium  bisulphite  is  formed  and  the  tartaric 
acid  liberated ;  (2 )  when  this  solution  is  heated  to  66°,  the  sulphurous  acid  is  expelled 
and  all  the  tartaric  acid  precipitated  as  pure  crystallised  calcium  tartrate;  (3)  if  in  (1) 
potassium  bitartrate  is  used  instead  of  calcium  tartrate,  potassium  bisulphite  and  tartaric 
acid  are  formed,  and  on  heating  the  liquid  to  80°,  sulphur  dioxide  is  evolved  and  pure 
potassium  bitartrate  separated  in  a  crystalline  state ;  (4)  potassium  tartrate,  when  treated 
with  calcium  bisulphite,  gives  potassium  bisulphite  and  calcium  bitartrate ;  the  latter 
separates  at  100°,  when  the  potassium  bisulphite  gives,  with  lime,  calcium  bisulphite  and 
caustic  potash,  which  can  also  be  utilised. 

In  practice  Gladysz  proposed  to  suspend  the  tartar  in  lumps  in  lead-lined  wooden 
vessels,  and  into  these — hermetically  sealed  and  arranged  in  a  series  of  five  or  six — to  pass 
sulphur  dioxide.  The  solutions  (10°  to  12°  Be. )  thus  obtained  are  sent  to  the  concentration 
apparatus,  which  communicates  with  towers  to  condense  the  sulphur  dioxide  (see  Vol.  I., 
p.  280).  When  the  latter  is  completely  evolved,  the  liquid  is  kept  at  125°  for  a  short  time 
to  separate  crystalline  calcium  tartrate,  which  is  collected  by  means  of  a  centrifuge,  while 
the  solution  is  concentrated  further  and  allowed  to  cool  in  shallow  lead-lined  wooden 
vessels  to  deposit  the  potassium  tartrate.  As  a  rule,  however,  the  hot  potassium  tartrate 
solution  is  treated  directly  with  calcium  chloride  and  a  little  lime,  so  that  it  yields  insoluble 
calcium  tartrate,  which  is  more  easily  separated.  From  this  calcium  tartrate,  pure 
tartaric  acid  is  then  obtained  in  the  ordinary  way.  Although  theoretically  no  sulphur 
dioxide  should  be  lost  in  this  process,  in  practice  about  15  per  cent,  is  lost  in  winter  and 
20  per  cent,  in  summer. 

The  Gladysz  process,  somewhat  modified  by  Ciapetti,  is  used  in  Italy  in  the  manufacture 
of  tartar  from  vinasse,  lees,  etc.  (see  p.  404). 

USES  AND  STATISTICS  OF  TARTARIC  ACID.  This  acid  is  used  in  considerable 
quantities  to  replace  the  more  expensive  citric  acid  in  the  preparation  of  beverages,  liquors, 
and  aerated  waters,  and  in  wine-making.  Large  quantities  are  consumed  in  the  mordanting 
of  wool  and  silk,  to  reduce  chromium  salts,  etc.,  in  the  printing  of  textiles,  manufacture 
of  dyes,  photography,  medicine,  etc.  Refined  tartaric  acid  pays  an  import  duty  in  Italy  of 
8s.  per  quintal  and  in  the  United  States  and  Spain  of  25  per  cent,  ad  valorem. 

Italy  possesses  the  following  large  tartaric  acid  factories :  at  Carpi,  Agnano  (Pisa), 
Barletta,  Milan,  and  Casalmonferrato  (the  last  of  these  was  transferred  to  Milan  in  1920). 
The  last  three  are  the  more  important,  and  are  able  to  produce  together  as  much  as  5000 
tons  per  annum. 

The  world's  production  in  1905  was  about  11,000  tons,  of  which  Italy  produced  670 
tons;  England  and  the  United  States,  each  more  than  2500;  Germany,  about  1500; 
France,  about  800  (1300  in  1910);  and  Austria-Hungary  about  1000  tons.  Germany 
exported  1700  tons  of  the  refined  acid  in  1908,  2100  in  1910,  1850  in  1911,  2673  in  1912, 
and  2956  in  1913;  the  imports  were  458  tons  in  1910,  379  in  1911,  428  in  1912,  and  325 
in  1913. 

For  Italy  the  imports  and  exports  are  as  follows  : 

1908      1910   1912      1913     1914     1915     1916      1917     1918 

T    T  ftons     .        138  298     146  40  20  87  26  0-7  2-5 

s  \value,  £       —        27,380      —          4,594       2,314     20,952       6,264          280        1,000 

TT™         /tons     •     ]>928       2>177   2>516        2'846       2>963       3>634       3'292       2>413        J'971 
5   \  value,  £  196,000      —      324,467   355,536   872,256   790,132   965,080    788,400 

Great  Britain  imported  1700  tons  of  tartaric  acid  in  1908,  2050  in  1910,  2000  in  1912, 
and  2300  in  1913,  and  exported  335  tons  in  1911  and  835  in  1913. 


410  ORGANIC     CHEMISTRY 

For  France  the  importation  and  exportation  are  as  follows  (tons ) : 

1913  1914  1915  1916 

Importation     ...         501  374  273  305 

Exportation     ...         .       1350  1073  1027  914 

In  1907,  four  Russian  factories,  worked  by  a  syndicate,  produced  600  tons  of  tartaric 
acid  and  sold  it  at  £200  per  ton. 

The  Argentine  imported  95  tons  of  tartaric  acid  in  1904,  465  in  1909,  729  in  1910,  and 
868  (almost  three-fourths  from  Italy)  in  1911.  In  1911  a  factory  capable  of  making  330 
tons  per  annum  was  erected  at  Buenos  Aires. 

The  price  of  tartaric  acid  is  variable  for  the  reasons  mentioned  on  p>  407.  Some  years 
before  the  war  the  price  was  about  £140  per  ton,  in  1911  it  approached  £100,  and  during 
the  war  it  rose  in  Italy  to  £360  or  even  £560  per  ton,  while  after  the  war  ended  in  1919 
it  varied  from  £440  to  £520  per  ton. 

ARTIFICIAL  TARTARIC  ACID.  In  1889  a  process  was  patented  by  Basset,  and  in 
1891  a  similar  but  improved  one  by  Naquet  for  obtaining  tartaric  acid  from  starch  (1  to 
5  of  water)  by  saccharifying  with  an  equal  weight  of  hot  sulphuric  acid  (51°  Be.),  then 
adding  double  this  quantity  of  sulphuric  acid  and  almost  as  much  sodium  nitrate  and 
heating  at  100°.  When  the  reaction  becomes  very  vigorous,  the  temperature  is  moderated 
and  the  heating  continued  at  80°  to  90°  for  two  to  three  days,  the  evaporated  water  being 
first  replaced  and  the  liquid  concentrated  to  a  syrup  when  evolution  of  gas  ceases.  In  this 
manner  all  the  saccharic  acid  is  decomposed;  the  sulphuric  and  oxalic  acids  are  then 
neutralised  with  calcium  carbonate  and  the  tartaric  acid  subsequently  worked  up  in  the 
usual  manner  by  way  of  its  calcium  salt. 

One  hundred  kilos  of  starch  should  give  theoretically  140  of  calcium  tartrate,  corre- 
sponding with  56  kilos  of  tartaric  acid,  but  in  practice  the  yield  of  the  acid  does  not  exceed 
55  to  60  per  cent,  of  this  theoretical  amount. 

TRIHYDROXYGLUTARIC  ACID,  CO2H  •  [CH(OH)]3  •  CO2H.  should  exist  in  four 
stereoisomeric  forms,  of  which  the  dextro-,  laevo-  and  racemic  (m.-pt.  127°)  compounds 
are  known.  They  are  obtained  by  the  oxidation  of  xylose  or  arabinose,  and,  on  reduction, 
give  glutaric  acid,  their  constitution  being  thus  confirmed. 

SACCHARIC  ACID,  CO2H  •  [CH(OH)]4-  CO2H,  forms  ten  stereoisomerides,  which  are 
all  known  and  are  closely  related  to  the  sugars.  Saccharic  acid  is  formed  as  a  rule  in  the 
oxidation  of  sucrose,  glucose,  mannitol,  and  starch  (e.  g.,  with  nitric  acid ).  It  is  deliquescent 
and  soluble  in  water,  and  when  heated  or  fused  is  converted  into  saccharone,  which  is  a 
dextro-rotatory  lactone  melting  at  about  150°. 

MUCIC  ACID,  CO2H  •  [CH(OH)]4  •  CO2H,  is  the  stereoisomeride  of  saccharic  acid  which 
is  constantly  inactive.  It  is  obtained  on  oxidising  lactose,  dulcitol,  gum,  etc.,  and  forms 
a  white  powder  very  slightly  soluble  in  water. 

KETONIC   DIBASIC   ACIDS 

Esters  of  these  acids,  like  those  of  /?-ketonic  acids  (ethyl  acetoacetate, 
etc. ;  see  p.  396),  show  both  ketonic  and  acid  decompositions,  and  also  a  new 
one  in  which  carbon  monoxide  separates. 

MESOXALIC  ACID  (Dihydroxymalonic  Acid),  CO2H  •  CO  •  CO2H  +  H20  or 
CO^H  •  C(OH)2  •  CO2H,  shows  ketonic  behaviour  in  agreement  with  the  first  formula,  but 
the  molecule  of  water  cannot  be  separated  from  the  deliquescent  prisms  even  at  100°,  and, 
further,  derivatives  (esters,  etc.),  are  known  which  correspond  better  with  the  second 
formula,  whilst  the  latter  also  explains  well  why  mesoxalic  acid,  when  heated  with  water, 
loses  C02  and  gives  glyoxylic  acid,  C02H  •  CH(OH)2.  The  structure  of  the  acid  likewise 
follows  from  its  formation  by  the  action  of  barium  hydroxide  on  ethyl  dibromomalonate  : 

CBr2(C02C2H5)2+  Ba(OH)2=  BaBr2+  C(OH)2(C02C2H5)2. 

Its  ketonic  constitution  is  confirmed  also  by  the  fact  that  it  gives  tartronic  acid, 
C02H  •  CH(OH)  •  C02H,  on  reduction. 

OXALACETIC  ACID  (Butanonedioic  Acid),  CO2H  •  CH2  •  C02  •  CO2H,  is  not  known  in 
the  free  state,  but  is  formed  as  ester  by  condensation  of  ethyl  oxalate  and  ethyl  acetate  in 
presence  of  sodium  ethoxide  (see  Ethyl  Acetoacetate).  It  also  splits  up  in  two  ways 


TRICARBALLYLIC    ACID  411 

according  as  it  is  treated  with  dilute  sulphuric  acid  (giving  pyruvic  acid,  CO2,  and  alcohol) 
or  with  alkali  (giving  oxalic  and  acetic  acids ).  Being  a  ketone,  it  forms  an  oxime. 

The  alcoholic  solution  is  coloured  dark  red  by  ferric  chloride  and  hence  corresponds 
with  the  enolic  form,  C2H5  •  O  •  CO  •  CH  :  C(OH)  •  C02C2H5.  This  ester,  like  ethyl  aceto- 
acetate,  is  used  in  many  syntheses,  the  hydrogen  of  the  methylene  group  being  replaceable 
by  sodium,  etc. 

ACETONEDICARBOXYLIC  ACID  (Pentanonedioic  Acid),  CO2H  •  CH2  •  CO  •  CH2  • 
CO2H,  forms  crystals  which  melt  at  135°,  losing  2CO2  and  giving  acetone.  It  is  formed 
by  the  action  of  concentrated  sulphuric  acid,  in  the  hot,  on  citric  acid  : 

CH2  •  C02H  CH2  •  C02H 


CH2  •  C02H  CH2  •  C02H 

Citric  acid 

The  constitution  of  citric  acid  is  shown  by  its  formation  from  acetonedicarboxylic 
acid  by  the  action  of  hydrogen  cyanide  and  subsequent  hydrolysis. 

The  hydrogens  of  the  two  methylene  groups  are  replaceable  by  sodium,  so  that  this 
acid  may  be  used  in  syntheses  similar  to  those  effected  by  ethyl  acetoacetate. 

DIHYDROXYTARTARIC  ACID,  C02H  •  CO  •  CO  •  CO2H  -f  2H20,  or,  better, 
CO2H  •  C(OH)2  •  C(OH)2  •  CO2H,  melts  and  decomposes  at  98°  and  forms  a  sodium  salt, 
which  is  sparingly  soluble  and  decomposes  readily  into  CO2  and  sodium  tartronate, 
C02H  •  CH(OH)  •  C02Na. 

It  is  obtained  by  the  action  of  nitrous  acid  on  an  ethereal  solution  of  pyrocatechol, 
guaiacol,  etc.,  and  also  by  the  spontaneous  decomposition  of  nitrotartaric  acid.  Sodium 
bisulphite  converts  it  into  glyoxal,  while  with  hydro xylamine  it  forms  the  dioxime  corre- 
sponding with  the  diketonic  form.  With  phenylhydrazinesulphonic  acid,  it  forms  tartrazine, 
a  beautiful  yellow  colouring-matter  largely  used  in  dyeing  wool  and  silk. 

Of  the  higher  ketonic  acids  the  following  may  be  mentioned  :  hydro- 
chelidonic  acid  (acetonediacetic  acid),  CO(CH2  •  CH2  •  C02H)2;  diaceiosuccinic 

CH3  •  CO  •  CH  •  C02H  CH(CO  •  CH  )  •  CO  H 

acid,  ;  a,nd  diacetylglutaric  acid,  CH2<~TT/nrk  rrtr\  nrfu 

CH3-CO-CH-C02H  (Hs)'  AH 

the  esters  of  which  give  rise  to  tetrahydrobenzene  derivatives  or,  in  presence 
of  ammonia,  to  pyridine  derivatives. 

G.  POLYVALENT   TRIBASIC   HYDROXY-ACIDS 

ETHANETRICARBOXYLIC  ACID,  C02H  •  CH2  •  CH(CO2H)2,  and  ASYM. 
PROPANETRICARBOXYLIC  ACID,  CO2H  •  CH2  •  CH2  •  CH(C02H)2.  These 
two  acids  are  stable  in  the  form  of  esters,  but  in  the  free  state  they  readily 
decompose,  liberating  C02  and  forming  dibasic  acids. 

TRICARBALLYLIC  ACID  (Symm.  Propanetricarboxylic  or  Pentadioic- 
3-methyloic  Acid),  CO2H  •  CH2  •  CH(C02H)  •  CH2  •  C02H,  melts  at  163°  and  is 
very  soluble  in  water. 

It  is  found  in  unripe  beets  and  occurs  abundantly  in  the  deposits  of  the 
vacuum  pans  of  sugar  factories.  Synthetically  it  is  obtained  from  aconitic 
acid  l  by  the  addition  of  hydrogen  and  from  citric  acid,  which  loses  its  hydroxyl 
group  when  treated  with  hydriodic  acid. 

CH  •  C02H 
II 

1  Aconitic  Acid  is  the  corresponding  unsaturated  acid,  C  •  C02H     .     It  melts  at  191°,  and  is 


CH., 


COjH 

readily  soluble  in  water ;  it  is  an  energetic  acid  and  is  converted  into  tricarballylic  acid  by  nascent 
hydrogen.     It  is  prepared  by  heating  dry  citric  aoid,  which  loses  a  molecule  of  water. 
It  occurs  naturally  in  the  sugar-cane,  beet,  Aconitum  napellus,  etc. 


412  ORGANIC     CHEMISTRY 

Its  constitution  is  shown  by  its  synthesis  from  glycerol  by  way  of  the 
tribromhydrin  and  tricyanohydrin,  C^H5(CN)3,  the  latter  being  hydrolysed 

CH2  .  CO2H 

OH 
CITRIC  ACID,   C<£Q  H 

CH2  .  C02H 

This  acid  is  deposited  from  its  aqueous  solutions — if  these  are  not  too 
hot — in  large,  rhombic  prisms  containing  1H2O,  which  is  given  up  partly  in 
dry  -air  and  completely  at  135°.  It  melts  in  its  water  of  crystallisation  at 
135°  and,  when  anhydrous  at  153°  and  at  a  higher  temperature  decomposes 
into  aconitic  and  itaconic  acids,  citraconic  anhydride,  C02,  and  acetone.  It 
is  readily  soluble  in  water  (135  :  100  at  15°  and  200  :  100  at  the  boiling-point)  1 
or  alcohol  (53  :  100  at  15°  and  about  double  as  much  in  80  per  cent,  alcohol), 
and  to  a  slight  extent  in  ether  (9:  100).  It  was  discovered  by  Scheele  in 
1784  and  studied  by  Liebig  in  1838.  It  occurs  abundantly  in  nature  in  the 
lemon  (4*5  per  cent,  in  the  unripe  lemon),  orange,  gooseberry,  and  other  fruits, 
and  in  small  quantities  in  cows'  milk,  the  shoots  and  leaves  of  the  vine,  tobacco, 
and  fungi,  and  as  calcium  salt  in  the  beet,  willow,  etc. 

Industrially  it  is  obtained  by  the  lime  method  described  later  (see  p.  415). 
Synthetically  it  may  be  prepared  from  acetonedicarboxylic  acid  by  the 
action  of  hydrocyanic  acid  and  subsequent  hydrolysis.  The  constitution 
thus  indicated  is  confirmed  by  its  formation  from  symm.  dichlorhydrin, 
CH2C1  '  CH(OH)  •  CH2C1,  which  on  oxidation  gives  symm.  dichloracetone, 
and  hence  by  the  introduction  of  cyanogen  groups  and  hydrolysis  yields  citric 
acid  : 

CH2C1                 CH2C1                 CH2C1                 CH2-CN  CH2'C02H 

(10 ^  ^OH ^     ^OH  ^OH       >       ^OH 

I  I  I       '°2H  I       '°2H  '°2H 

CH2C1  -CH2C1  CH2C1  CH2-CN  CH2-C02H 

Citric  acid  was  prepared  some  years  ago  (Fabrique  de  produits  chimiques 
de  Thann  et  de  Mulhouse)  by  Wehmer's  biological  process  (Ger.  Pat.  72,957 
of  1893),  according  to  which  glucose  is  fermented  by  certain  moulds  (Citromyces 
Pfefferianus  and  Glaber,  and  Mucor  pyriformis),  the  yield  being  about  55  per 
cent,  of  the  sugar.2 

1  The  following  table  gives  the  percentage  by  weight  in  aqueous  solutions  of  different 
densities  : 

Degrees  Baume      .        .246     10-5     12     14     18     22     26    28    30     32     34 
Per  cent,  of  citric  acid .     4     8     12       20      22     26     34    42     50     54     58     62     6fi 

*  The  formation  of  citric  acid  by  the  action  of  micro-organisms  on  sugar  was  studied  in 
detail  also  by  Maze  and  Perrier  in  1904,  by  Herzog  and  Polotzky  in  1909,  and  by  Buchner  arid 
Wiistenfeld  in  1909  with  Citromyces  citricus.  Allthese  authors  found  that  such  organisms  are 
able  to  live  in  highly  acid  media  and  that,  under  certain  conditions,  especially  when  there  is  a 
scarcity  of  nutrient  nitrogenous  substances,  they  can  transform  as  much  as  50  per  cent,  of  the 
sugar  into  citric  acid.  A  current  of  air  passed  through  the  fermenting  liquid  does  not  aid  the 
development  of  the  organisms,  but  at  the  same  time  does  not  oxidise  the  citric  acid  formed  ; 
lack  of  air,  however,  retards  the  fermentation.  The  presence  of  inorganic  ammonium  salts  and 
of  calcium  carbonate  results  in  a  good  yield  and  in  good  separation  of  calcium  citrate.  Various 
tests  were  made  with  20  per  cent,  solutions  of  sugar  (sucrose,  which  is  rapidly  inverted )  containing 
0-5-1  per  cent,  of  inorganic  salts  (ammonium  phosphate  or  nitrate,  etc.);  in  ten  to  twelve 
days  or,  in  some  cases,  in  thirty -five  days,  40  to  50  per  cent,  of  the  sugar  undergoes  conversion 
into  calcium  citrate  (Wehmer,  1912).  The  formation  of  the  citric  acid  by  direct  oxidation  (as 
occurs  in  acetic  or  oxalic  fermentation)  is  excluded,  and  Maze  advances  the  hypothesis  that  the 
acid  is  derived  rather  from  the  decomposition  of  Jthe  protein  substances  forming  the  ferments 
themselves,  whilst  Buchner  assumes  the  intermediate  formation  of  parasaccharinic  acid.  , 

Wehmer  (1913)  confirms  the  observation  of  earlier  experimenters  that  calcium  citrate  is 


CITRUS    INDUSTRY  413 

When  heated  for  a  long  time  with  water,  citric  acid  forms  a  little  aconitic 
acid,  into  which  it  is  transformed  completely  by  concentrated  hydrochloric 
acid.  It  is  readily  oxidised  to  acetone,  oxalic  acid,  and  carbon  dioxide. 

Like  tartaric  acid,  citric  acid  hinders  the  precipitation  of  the  metallic 
hydroxides  from  their  salts  by  ammonia.1 

Citric  acid  is  used  in  large  quantities  for  lemonade  and  in  pharmacy  and  for  effervescent 
drinks  (citrate  of  magnesia);  it  is  employed  also  in  dyeing  and  in  textile  printing.  It  is 
used  also  in  aqueous  solution  (or  as  fresh  lemon  juice)  as  a  substitute  for  vinegar.  It  is 
often  employed,  in  preference  to  tartaric  acid,  to  increase  the  acidity  of  wine  so  as  to  improve 
its  colour  and  keeping  qualities  (100  grams  per  hectolitre  is  sufficient,  whereas  about  400 
grams  of  tartaric  would  be  necessary  to  produce  the  same  effect,  since  two-thirds  of  it 
undergoes  precipitation  as  potassium  bitartrate).  A  certain  amount  of  citric  acid  is  used 
in  the  analysis  of  superphosphates. 

CITRUS   INDUSTRY 

Citric  acid  is  manufactured  from  the  juice  of  lemons  yielded  especially  by  the  following 
three  plant  species :  Citrus  limonium,  Citrus  bergamia  (bergamot),  and  Citrus  limetta  (or 
wild  lemon  cultivated  by  the  British  in  Guiana  and  the  West  Indies).  Lemons  are 
cultivated  most  extensively  in  Sicily  and  Calabria,  and  to  a  considerable  extent  also  in 
Spain.  The  cultivation  is  of  little  importance  in  Greece,  the  Sandwich  Islands,  and  the 
West  Indies,  but  is  rapidly  increasing  in  Australia.  During  recent  years  the  production 
of  oranges  and  lemons  has  made  rapid  strides  in  California  and  in  Florida,2  where  it  is 

obtainable  in  good  yield  also  from  glycerol,  and  finds  also  that  citric  acid  is  produced 
only  as  calcium  citrate  (i.  c.,  in  presence  of  calcium  carbonate)  and  never  aa  free  acid, 
possibly  because  the  latter  undergoes  instantaneous  decomposition  or  transformation  into  other 
substances  (not  into  organic  acids);  in  any  case  the  biological  formation  from  glycerine  denotes 
the  possibility  of  a  synthetic  process,  which  is  somewhat  rare  (see  p.  137).  From  lactose  and 
ethyl  alcohol  citric  acid  has  not  been  prepared. 

According  to  Zahorski  (U.S.  Pat.  1,069,168,  1913)  citric  acid  may  be  obtained  from  sugar 
(glucose,  levulose,  etc.)  by  adding  15  per  cent,  of  citric  acid  to  a  culture  of  Sterigmatocystis  nigra 
and  using  this  culture  for  the  gradual  seeding  of  the  saccharine  solution. 

1  Tests  and  Reactions  for  Citric  Acid.    Deniges  reaction  is  characteristic  and  serves  to  detect 
small  quantities  of  the  acid ;  the  solution  is  heated  to  boiling  -with  one-twentieth  of  its  volume 
of  Deniges'  reagent  (5  grams  of  mercuric  oxide,  80  c.c.  of  water,  and  20  c.c.  of  concentrated  sulphuric 
acid ),  3  to  10  drops  of  approximately  decinormal  potassium  permanganate  solution  being  added ; 
a  white,  crystalline  precipitate  is  formed  immediately  even  with  traces  of  citric  acid.     The 
reaction  is  not  masked  by  the  presence  of  tartaric,  oxalic,  malic,  sulphuric,  or  phosphoric  acid, 
although  the  amount  of  permanganate  used  must  then  be  slightly  increased. 

Haussler  (1914)  gives  the  following  reaction  for  detecting  small  amounts  of  citric  acid  even 
in  presence  of  other  organic  acids  (proteins  and  sugars  are  first  eliminated  by  successive  treat- 
ment with  lead  acetate,  H2S  and  calcium  carbonate) :  2  c.c.  of  the  dilute  citric  acid  solution 
(even  0-1  per  cent.)  is  evaporated  to  dryness  in  a  dish  with  2  c.c.  of  alcohol  containing  a  little 
vanillin,  3  to  4  drops  of  25  per  cent,  sulphuric  acid  being  added  to  the  residue  and  the  dish  heated 
for  fifteen  minutes  on  a  water-bath  :  the  mass  then  becomes  an  intense  violet  and  dissolves  in 
water  to  a  green  solution,  which,  even  in  high  dilution,  is  coloured  an  intense  red  by  addition 
of  ammonia. 

The  presence  of  tartaric  acid- — -which  is  a  common  adulterant — in  citric  acid  may  be  detected 
by  the  addition  of  potassium  acetate,  the  acid  potassium  citrate  thus  formed  being  readily 
soluble,  whilst  acid  potassium  tartrate  is  only  slightly  soluble.  Minimal  quantities  of  tartaric 
aoid  may  be  also  detected  as  follows  :  1  gram  of  the  powdered  substance  is  heated  for  a  few 
minutes  on  the  water-bath  with  1  c.c.  of  20  per  cent,  ammonium  molybdate  solution  and  a  few 
drops  of  0-25  per  cent,  hydrogen  peroxide  solution;  in  presence  of  even  0-001  gram  of  tartaric 
acid,  a  bluish  coloration  is  obtained.  The  presence  of  oxalic  acid  is  easily  discovered,  since 
in  the  cold  and  in  arnrnoniacal  solution  calcium  oxalate  is  insoluble,  whilst  calcium  citrate  is 
soluble. 

2  The  lemon  orchards  in  Sicily  are  found  especially  on  the  coast  from  Palermo  to  Cefalu 
(about  one-fifth  of  the  total  production  of  lemons  and  oranges)  and  on  the  coast  near  Messina 
(more  than  double  that  of  Palermo-Cefalu),  usually  on  irrigated  lands,  but  sometimes  in  cool 
non-irrigated  districts.     The  stocks  are  obtained  from  the  seed  of  the  wild  orange  (called  by  the 
Sicilians  arancio  agro,  or  sour  orange ).     The  plants  from  these  seeds  are  planted  out  in  the  orchards 
in  their  third  year  and  are  placed  from  3  to  5  metres  apart,  according  to  the  nature  of  the  soil, 
to  the  wind,  and  to  custom.     After  a  year  the  stock  is  grafted  from  an  adult  plant.     Fructifi- 
cation occurs  after  a  further  three  years  and  reaches  its  maximum  in  ten  years.     The  flowering 


414  ORGANIC    CHEMISTRY 

already  about  double  that  of  Sicily.  It  is  pleasing  to  note  that  plantations  of  oranges 
alone  are  being  more  and  more  largely  replaced  by  those  of  lemons. 

In  German  East  and  West  Africa,  plantations  of  lemons  were  advantageously  replacing 
those  of  rubber  before  the  war. 

Only  the  refuse  lemons  (one-fourth  of  the  total  production)  are  used  for  the  manufacture 
of  citric  acid,  as  they  cost  only  one-half  as  much  as  the  picked  fruit. 

The  first  operation  to  which  the  lemons  are  subjected  is  peeling,  a  workman  removing 
the  peel  with  three  cuts  of  a  knife,  cutting  the  lemon  in  two  and  throwing  it  into  a  tub ; 
the  peel  is  collected  separately  for  the  preparation  of  essence.  A  skilled  operative  can 
peel  more  than  4000  lemons  a  day.  From  8000  lemons,  pressed  in  a  suitable  press,  700  litres 
of  juice,  containing  4-5  to  6  per  cent,  of  citric  acid,  are  obtained;  only  9  to  10  per  cent, 
of  the  total  acid  exists  as  calcium  citrate.1  The  juice  does  not  keep  well  (better  if 

of  the  lemons  on  the  same  plant  is  progressive  and  lasts  the  whole  of  May ;  from  the  latter  half  of 
June  to  the  beginning  of  October  the  plants  are  watered  every  fortnight.  The  maturation 
of  the  fruit  is  gradual  from  November  to  the  end  of  April  and  the  harvest  is  gathered  in  three 
periods,  the  best  fruit  being  those  of  the  middle  one — December  to  February;  the  last  fruit, 
plucked  in  April  and  the  beginning  of  May,  are  poorer  in  juice  and  thicker  in  the  peel.  In  the 
coast  district  of  Messina,  the  harvest  finishes  at  the  beginning  of  March. 

Lemons  have  also  been  forced  in  Sicily  during  the  past  few  years,  the  highly  valued  summer 
fruit  being  thus  obtained;  these  are  called  verddli  (high  quality)  and  bianchetti  (lower  quality). 
In  this  case  the  plants  are  not  watered  during  June  and  July,  the  leaves  withering  and  all  the 
young  fruit  .falling.  In  August,  water  in  abundance  is  given  at  intervals,  and  Sodium  nitrate 
applied  as  fertiliser.  The  plant  then  suddenly  becomes  very  vigorous,  and  in  a  few  days  is 
covered  with  new  flowers,  the  fruit  ripening  rapidly  from  the  end  of  May  to  the  close  of  the 
summer,  and  that  gathered  in  June  or  July  being  of  the  highest  quality.  Such  plants  give  an 
increased  crop,  especially  if  manured,  and  the  fruit  commands  more  than  double  the  ordinary 
prices.  This  procedure  is  followed  in  orchards  where  the  soil  is  not  moist  and  can  be  left  to 
dry  completely  and  where  the  lemons  are  not  alternated  with  oranges  or  other  crops  requiring 
watering. 

Under  favourable  conditions,  a  good  lemon  plant  should  yield  on  an  average  1000  lemons 
a  year  (some  very  large  plants  give  several  thousands).  The  price  varies  considerably,  8.9.  to 
IQs.  per  1000  being  paid  for  the  fruit  on  the  tree  and  as  much  as  24s.  for  the  gathered  fruit; 
forced  lemons  cost  at  least  20s.  per  1000,  the  price  in  1907  exceeding  40s.  The  cost  of  gathering, 
packing,  and  freight  to  the  port  varies  from  Is.  Id.  to  3s.  2d.  per  1000.  The  refuse  lemons,  which 
form  about  one-fourth  of  the  crop  (or  more  if  the  demand  for  lemons  is  small),  cost  about  half 
as  much  as  the  other  fruit  (5s.  to  6s.  per  1000  on  the  average),  although  on  rare  occasions  the 
price  reaches  8s.,  and  in  1908,  at  the  height  of  the  crisis,  it  fell  to  2s.  per  1000. 

1  Fresh  lemon  juice,  contains  also  7  to  9  per  cent,  of  glucose,  0-2  to  0-8  per  cent,  of  saccharose 
(according  as  the  lemons  are  sour  or  ripe),  certain  extractive,  gummy,  and  pectic  substances 
(about  0-2  per  cent,  for  ripe  and  0-8  per  cent,  for  unripe  fruit),  and  about  0-5  to  0-7  per  cent,  of 
inorganic  salts.  The  presence  of  these  substances  renders  it  impossible  to  crystallise  the  citric 
acid  merely  by  concentrating  the  juice,  even  when  all  the  glucose  is  transformed  into  alcohol 
(5  to  6  per  cent.),  so  that,  even  at  the  present  time,  the  citric  acid  is  separated  by  Scheele's 
classical  and  rather  costly  process,  according  to  which  it  is  first  converted  into  calcium  citrate. 
The  high  price  of  fuel  has  prevented  the  establishment  of  the  citric  acid  industry  in  Sicily,  and 
the  preparation  of  the  acid  has  been  monopolised  for  a  long  time  by  England  and,  at  the  present 
time,  largely  by  Germany.  Both  these  countries  receive  the  raw  material  from  Sicily,  to  a  small 
extent  as  lemons  packed  in  barrels  containing  sea -water,  partly  as  concentrated  juice  (agro 
cotto),  but  mostly  as  calcium  citrate. 

In  consequence  of  the  development  of  lemon -growing  in  Spain,  and  especially  in  California 
and  Australia,  and  also  owing  to  an  agreement  entered  into  by  the  manufacturers  of  citric  acid, 
the  condition  of  the  Sicilian  growers  became  so  critical  that  in  1903  the  Italian  Minister  of 
Agriculture  offered  a  prize  of  £6000  for  improvements  in  the  industry  or  new  processes  of  value 
to  the  cultivators.  This  sum  was  largely  wasted  by  Commissions  who  achieved  nothing  or  by 
rewarding  certain  favoured  individuals.  However,  at  the  end  of  1904,  Professor  Restuccia, 
of  Messina,  announced  to  the  Government  the  discovery  of  a  process  for  the  direct  extraction  of 
citric  acid  by  simple  concentration  of  the  juice,  to  which  was  previously  added  a  trace  of  a 
substance — the  nature  of  which  he  did  not  reveal  (picric  acid  !) — and  a  little  animal  charcoal, 
but  this  process  only  led  to  further  waste  of  money. 

In  1910,  Peratoner  and  Scarlata  suggested  the  following  new  process  for  extracting  the 
essence  and  citric  acid  from  the  lemons  directly,  without  conversion  of  the  acid  into  the  calcium 
salt.  The  juice  obtained  by  squeezing  the  minced  lemons  in  hydraulic  presses  is  partly  distilled 
in  a  vacuum  on  a  water-bath  at  60°  to  recover  the  essence  and  then  concentrated  in  vacua  at 
70°  until  it  acquires  a  syrupy  consistency  (one-tenth  of  the  original  weight).  When  the  syrup 
is  cold,  all  the  citric  acid  is  extracted  by  treatment  with  a  mixture  of  alcohol  and  ether,  in  which 
many  of  the  impurities  are  insoluble.  The  alcohol  and  ether  are  recovered  by  distillation,  and 
the  residue  diluted  with  a  little  water,  filtered,  and  concentrated  in  vacua ;  after  standing  for 
twelve  to  twenty-four  hours  it  sets  to  a  yellowish  red  crystalline  mass  which,  after  defecation 
and  decolorisation  in  the  ordinary  way  (animal  charcoal,  etc.),  gives  pure  colourless  crystals, 


OILOFLEMON  415 

pasteurised  at  63°  to  65°),  and  is  usually  concentrated  at  once  in  open  pans  with  direct- fire 
heating  until  the  specific  gravity  reaches  60°  on  the  citro meter  (1-2394,  or  28°  Be.),  and  the 
product  represents  a  blackish  decoction  containing  300  to  4.00  grams  of  citric  acid  per  litre 
(that  from  the  bergamot  of  Calabria  and  Messina  contains  300  grams,  while  that  produced 
in  the  Sandwich  Islands  and  in  the  Republic  of  Dominica  from  lemons  of  the  limetta  species 
has  a  density  of  1-32  and  contains  about  575  grams  of  citric  acid  per  litre).  The  boiling 
decoction  is  passed  through  a  cloth  and  is  collected  in  casks  for  transport. 

The  commercial  value  of  the  juice  (agro  cotto)  depends  on  the  content  of  citric  acid, 
and  is  determined  either  by  diluting  the  juice  and  titrating  with  normal  caustic  soda  or 
by  precipitating  in  the  hot  as  calcium  citrate  and  weighing  the  latter.  This  estimation 
is  preceded  by  a  qualitative  examination  to  ascertain  if  salt  has  been  added  to  increase 
the  specific  gravity  (test  with  silver  nitrate  in  presence  of  a  little  nitric  acid)  or  if  sulphuric 
or  hydrochloric  acid  has  been  added  to  raise  the  degree  of  acidity  (test  with  silver  nitrate 
or  barium  chloride  in  presence  of  a  little  nitric  acid). 

In  the  large  modern  factories,  the  juice  is  treated  in  almost  the  same  manner  as  in  the 
manufacture  of  tartaric  acid  (see  p.  407) :  into  100-hectolitre  masonry  vessels  provided  with 
stirrers  and  cold-water  coils  are  placed  20  hectolitres  of  concentrated  juice  and  80  hectolitres 
of  water,  the  liquid  being  then  well  mixed  for  thirty  minutes  and  allowed  to  ferment,  the 
glucose  being  thus  converted  into  alcohol  and  the  juice  clarified.  By  passing  very  cold 
water  through  the  coil  the  temperature  of  the  liquid  is  lowered  to  5°,  and  a  large  part 
of  the  dissolved  and  suspended  extractive  and  mucilaginous  matters  separated ;  in  presence 
of  a  little  tannin,  these  matters  coagulate  *nd  do  not  redissolve  (50  litres  of  sumach  extract 
at  10°  Be.  are  sufficient,  the  liquid  being  stirred  for  fifteen  to  twenty  minutes  immediately 
after  the  addition).  The  solution  is  then  passed  to  the  filter-presses  and  thence  into 
20-hectolitre  wooden  vats  or  into  brickwork  vessels  similar  to  the  preceding  ones,  but 
provided  with  perforated  coils  for  direct-steam  heating.  The  boiling  liquid  is  now 
neutralised  exactly  with  dense  milk  of  lime  or  with  powdered  calcium  carbonate.  The 
latter  causes  frothing  and  sometimes  overflow  of  the  liquid,  but  precipitates  a  purer 
calcium  citrate,  whilst  the  hydroxide  throws  down  many  pectic  and  colouring  matters. 
In  some  cases  two-thirds  of  the  acidity  is  neutralised  with  calcium  hydroxide  and  the 
remainder  by  the  carbonate.  For  every  100  kilos  of  citric  acid  present  (titrated)  45  kilos 
of  quicklime  (57  of  slaked  lime  or  80  of  the  carbonate)  are  added.  After  stirring  while 
hot,  the  insoluble  tricalcic  citrate — which  forms  immediately — is  passed  at  once  through 
the  filter-presses  and  washed  for  ten  minutes  with  very  hot  water,  for  ten  minutes  with 
tepid  water,  and  for  five  minutes  with  cold  water,  which  should  remain  almost  colourless. 
In  some  parts  of  Sicily,  calcium  citrate  is  prepared  in  a  primitive  method  (with  slaked  lime 
often  containing  magnesia,  which  yields  soluble  magnesium  citrate,  this  being  lost)  and 
is  sold  dry  with  a  content  of  64  per  cent,  of  citric  acid.  300  kilos  of  calcium  citrate  of  this 
strength  require,  on  the  average,  100,000  lemons,  the  peel  of  which  yields  37  kilos  of  essence, 
selling  at  6*.  4d  per  kilo.1  The  total  cost  of  manufacturing  calcium  citrate  and  essence 

the  yield  being  60  to  70  per  cent.  The  remaining  acid  may  be  separated  from  the  mother-liquor 
as  citrate. 

In  spite  of  the  favourable  opinion  expressed  by  Professors  Garelli  and  Paterno,  this  process 
does  not  seem  to  have  been  applied  practically. 

Meanwhile  the  crisis  in  the  citrus  industry,  which  had  apparently  lessened  as  a  result  of  the 
good  crops  and  prices  of  1906  and  1907,  became  aggravated  in  190.8  owing  to  the  diminished 
demand  for  lemons,  to  the  American  crisis,  to  the  agreement  between  the  producers  of  citric 
acid  to  limit  the  amount  of  raw  material  required — thus  lowering  prices  and  exhausting  the 
usual  stocks  of  treated  products — and,  finally,  to  the  abundant  production,  since  refuse  lemons 
did  not  sell  for  2s.  Gd.  per  1000  at  the  beginning  of  1908  and  did  not  pay  for  gathering. 

Various  measures  have  been  taken  by  the  Italian  Government  to  protect  the  citric  acid  industry 
in  Sicily,  but  it  should  be  possible,  in  the  present  advanced  condition  of  technical  chemistry, 
to  develop  this  industry  without  such  aid.  The  sulphuric  acid  required  is  now  made  in  Sicily 
itself,  and  by  the  use  of  multiple-effect  evaporating  plant,  the  consumption  of  coal  may  be  reduced 
to  a  minimum.  In  1911  a  large  citric  acid  factory  was  erected  in  the  vicinity  of  Palermo  by  the 
firm  of  Golden  berg,  from  Winckel,  near  Wiesbaden  (see  later). 

1  Oil  of  lemon  is  extracted  from  the  skin  and  peel  by  pressing  the  latter  by  hand  against  a 
sponge  and  then  separating  the  liquid  from  the  sponges ;  this  liquid  deposits  the  residues  on 
standing  and  is  afterwards  decanted  off  and  filtered.  In  place  of  this  hand -pressing,  which 
yields  0-15  per  cent,  of  oil,  special  machines  are  used  in  some  factories.  From  the  waters  (on 
standing)  and  from  the  residues  remaining  after  decantation  (by  pressing),  an  inferior  oil  is 
recovered.  Distillation  of  such  waters  yields  distilled  oil,  which  is  not  ot  very  high  quality. 


416  ORGANIC    CHEMISTRY 

from  100,000  lemons  was,  before  the  war,  about  £10.  The  cakes  of  calcium  citrate  from 
the  filter-presses  are  mixed  in  20-hectplitre  lead-lined  vessels  with  15  hectolitres  of  cold  water, 
the  lime  of  the  citrate  being  then  neutralised  exactly  with  dilute  sulphuric  acid  (1  :  5) 
(with  100  kilos  of  citric  acid  in  the  juice  correspond  400  kilos  of  this  dilute  acid);  a  slight 
excess  of  sulphuric  acid  is  always  added,  since  the  presence  of  unaltered  calcium  citrate 
would  hinder  the  crystallisation  of  the  citric  acid. 

The  acid  is  added  in  portions  at  the  rate  of  5  litres  per  minute,  the  liquid  being  kept 
well  mixed  and  direct  steam  applied  through  a  perforated  leaden  coil.  The  mass  is  boiled 
for  ten  to  fifteen  minutes,  the  steam  being  then  suspended  and  the  whole  mixed  for  thirty 
minutes.  The  calcium  sulphate  is  then  removed  by  means  of  a  filter-press  and  is  washed 
with  200  litres  of  boiling  water,  which  is  added  to  the  first  filtrate,  and  then  with  cold 
water,  which  is  afterwards  used  for  treating  fresh  calcium  citrate.  The  citric  acid  solutions 
from  the  filter-presses  contain  only  minimal  quantities  of  sulphuric  acid  and  certain 
blackish  extractive  matters.  Concentration  of  the  solution  was  formerly  carried  out  in 
lead-lined  wooden  vessels,  4  metre's  long,  2  metres  wide,  and  25  cm.  deep,  containing 
closed  steam  coils.  Evaporation  should  be  rapid  and  the  temperature  should  never 
exceed  65°  to  70°.  When  the  liquid  reaches  46°  (sp.  gr.  1-3),  almost  all  the  calcium 
sulphate  previously  remaining  in  solution  separates;  the  clear  liquid  is  then  siphoned 
into  a  similar  vessel  underneath,  the  concentration  being  continued  until  a  crystalline 
skin  forms  at  the  surface  of  the  liquid,  which  is  next  transferred  to  wooden  crystallising 
vessels,  2  metres  X  70  cm.  x  20  cm.  (deep) ;  the  inner  surface  is  polished  with  plumbago. 
After  two  days,  the  dark  brown  mother-liquors  are  removed  and  the  yellowish-brown 
crystals  centrifuged.  In  order  to  separate  traces  of  dissolved  iron  from  the  mother-liquor, 
this  is  treated  with  a  little  potassium  f errocyanide  and  filtered ;  two  or  three  further  crops 
of  dark- coloured  crystals  are  obtained,  the  very  dark  mother-liquor  finally  obtained  being 
added  to  fresh  lemon- juice. 

In  modern  factories  the  citric  acid  solution,  freed  from  calcium  sulphate  by  filter- 
pressing,  is  concentrated  in  vacuum  apparatus,  just  as  in  the  sugar  and  tartaric  acid 
industries,  the  density  45°  to  50°  Be.  in  the  hot  being  attained.  In  this  way,  the  temperature 
does  not  exceed  60°  to  65°,  and  with  a  triple-effect  apparatus  not  only  rapidity,  but  also 
economy  of  fuel  is  attained  (see  Vol.  I.,  pp.  563,  568,  and  also  section  on  Sugar). 

In  order  to  remove  the  calcium  sulphate  remaining  in  solution,  the  concentration  is 
effected  in  two  phases  :  in  the  first  to  26°  to  28°  Be.,  the  liquid  being  then  cooled  in  suitable 
vessels  in  which  the  gypsum  deposits;  the  residual  liquid  is  then  concentrated  further  to 
48°  to  50°  Be.  This  liquid  is  discharged  into  the  crystallising  vessels,  which  are  of  lead-lined 
wood  and  of  large  surface;  the  mother- liquors  are  reconcentrated  and  recrystallised  two 
or  three  times,  and  are  finally  worked  up  to  crude  calcium  citrate.  The  blocks  of  crystals 
left  in  the  crystallising  vessels  are  broken  up  with  wooden  mallets  and  centrifuged. 

In  1912,  Messrs.  Schimmel  and  Company  obtained  a  yield  of  0-3  per  cent,  of  the  oil  from  the 
peel  by  chopping  the  latter  fine,  making  a  liquid  paste  with  water  and  distilling  at  a  pressure  of 
50  to  60  mm.;  oil  thus  prepared  does  not  keep  so  long  as  the  pressed  oil  (at  most  a  year). 
Immature  lemons  gathered  in  December-February  yield  the  finest  essence  (about  450  grams  per 
1000  lemons).  The  oil  is  stored  in  tinned  copper  vessels  and  is  sold  by  the  old  English  pound 
of  12  ounces  or  318  grams.  Its  density  is  0-854  to  0-861,  and  its  rotatory  power  +  60°  to  +  64° 
in  a  10  cm.  tube  at  20°,  and  it  distils  mostly  between  173°  and  178°.  It  is  yellow  and  undergoes 
change  in  the  air  and  light.  It  dissolves  easily  in  absolute  alcohol,  ether,  benzene,  or  5  vols. 
of  90  per  cent,  of  alcohol.  It  contains  about  90  per  cent,  of  limonene  and  5  to  8  per  cent,  of 
citral,  and  it  is  often  adulterated  with  oil  of  turpentine,  lemon  terpenes  or  oil  of  orange.  By  a 
law  passed  in  1897,  such  adulteration  is  forbidden. 

Deterpened  essence,  obtained  by  distilling  from  the  oil  in  a  vacuum  80  to  90  per  cent,  of  the 
terpenes  and  distilling  the  residue  in  a  current  of  steam,  is  a  yellow  oil  of  sp.  gr.  0-89,  with  an 
intense  smell  of  lemons,  and  is  highly  soluble  in  alcohol;  it  consists  mostly  of  citral. 

Its  exportation,  for  making  perfumes,  pastry  and  beverages  is  as  follows  (kilos) : 

1908                                              1910                          1912                        1913  1914 

Oil  of  orange        .     173,265  (£152,473)  143,285              53,803              48,103  42,838 

„      bergamot  .       74,842    (£95,798)               64,788              71,343              63,093  61,757 

„     lemon         .     476,842  (£228,884)  425,076  517,596  456,303  603,000 

1915                             1916                            1917  1918 

Oil  of  orange        .      '  70,672                  96,057                  72,347  312,820     (£557,948) 

„      bergamot  .       105,553  157,165  133,800  821,809  (£2,136,703) 

,.      lemon         .       744,000  655,522  522,486  1,629,740      (£717,086) 


CITRUS    INDUSTRY    STATISTICS 


417 


The  brown  crystals  first  obtained  are  refined  and  decolorised  by  dissolving  them  in 
rather  more  than  double  their  weight  of  water  (to  a  solution  of  20°  Be.)  and  boiling  the 
solution  with  animal  charcoal  previously  treated  with  hydrochloric  acid,  as  already 
mentioned  in  considering  the  refining  of  tartaric  acid  (p.  404). 

The  hot  liquid  is  filter-pressed  under  low  pressure  and  is  re-filtered  until  it  becomes 
clear  and  free  from  particles  of  charcoal.  The  filtrate  is  concentrated  in  a  vacuum  at 
about  60°  to  65°  until  crystals  of  citric  acid  form,  and  is  then  heated  to  90°  and  discharged 
into  lead-lined  wooden  crystallising  vessels,  in  which  it  is  stirred  at  intervals  so  as  to  obtain 
small  crystals ;  after  forty-eight  hours  these  are*  centrifuged  and  washed  in  the  centrifuge 
with  pure  citric  acid  solution,  just  as  is  done  with  sugar  (see  later). 

If  chemically  pure  citric  acid  free  from  metals  is  required,  the  concentration  is  carried 
out  in  thickly-tinned  vessels  and  the  crystallisation  in  wooden  vessels ;  the  traces  of  iron 
present  are  eliminated  by  addition'of  a  little  potassium  ferrocyanide  and  sodium  sulphide. 

In  all  the  washing  and  refining  operations,  pure  water  with  little  hardness  is  always 
employed. 

STATISTICS  AND  PRICES.  The  importance  of  the  Italian  citrus  industry  is  shown 
by  the  following  figures  : 


1909 

Output  of  citrus  fruits  (tons)   .        8,400 
Area  under  cultivation  (hectares)       - — 
Exportation  of  oranges  (tons)  .     110,899 
„  value.fi        .          .  .  443,600 

„  of  lemons  (tons)    .     256,063 


value  J  £ 


1911  1913  1914  1915  1916  1917    1918 

7,865  8,765  8,016  7,591  7,000  .—     — 

113,000  108,400  —  108,400  —  —     — 

128,343  130,600  133,080  129,161  104,290  34,662    42,558 

924,080  1,044,802  1,330,805  1,291,614  1,251,480  830,856  406,880 

258,689  304,541  308,389  204,992  209,804  150,291    91,169 


921,826  1,448,660  1,949,062  2,220,400  1,639,938  1,678,440  2,104,072  2,176,368 


Spain  exported  92,900  tons  of  oranges  in  1889,  300,000  tons  in  1899,  470,400  tons  in 
1908,  and  500,000  tons  (about  £2,200,000)  in  1912. 

Before  the  war  France  produced  about  2000  tons  of  oranges  per  annum. 

In  1912  California  exported  400,000  tons  of  oranges. 

In  Florida  the  orange  crop  amounted  to  about  170,000  tons  (5,000,000  boxes)  in  1894- 
1895j  but  the  exceptional  frost  of  the  following  winter  destroyed  almost  all  the  trees 
and  the  crop  was  reduced  to  2500  tons.  The  trees  were  afterwards  replaced  and  the  crop 
reached  about  165,000  tons  (£880,000)  in  1909  and  almost  270,000  tons  in  1912-1913. 

The  citric  acid  imported  into  and  exported  from  Italy  (Calabria  and  Sicily)  was  as 
follows  : 

1908    1910    1912     1913     1914      1915 

Imports  (tons)        164     109         127         105  32  18 

Value,  £         .  24,332          -    18,870  7,040       5,370 

Exports  (tons)        2-3      0-8         2-3        220  599          755 


1916 

26 

7,890 
1,045 


1917 


1918 


832 


754 


Value,  £ 


—       32,634    131,736    226,650    313,380    349,440    316,596 


The  output  of  citric  acid  in  Italy  in  1912  was  still  below  200  tons,  and  in  1914  it  reached 
800  tons,  the  capacity  of  the  factories  being  1600  tons. 

The  Sicilian  exports  and  imports  of  calcium  citrate  (in  casks  called  pipes,  holding 
305  kilos)  2  were  as  follows  (especially  to  the  United  States,  France,  and  Great  Britain)  : 

1905    1908    1910     1912     1913    1914     1915     1916    1917     1918 

Tons   .    .  4126   7710'  6476   7680   3813   5688   6704   7279   5838   3736 
Value  X  £1000  181    401   414   488   242   428   509   553    724   463 


1  While  in  other  years  the  picked  lemons  for  use  as  fruit  sold  for  12s.  or  even  16s.  per  1000 
(i.  e.,  1J  cantaros  =  about  125  kilos),  and  the  forced  fruit  for  as  much  as  32s.,  the  quotations 
in  July  1908  were  as  follow  :  ripe  lemons  (gathered  in  winter  and  spring),  5s.  4rf.  to  8s.  per  1000  ; 
verdelli,  17s.  Qd.  to  20s.  ;    bianchetti,  8s.   to   10s.  ;   for  pressing,  2s.  to  2s.  4d.     Subsequently 
prices  have  always  been  higher. 

2  M.  Spica  (1910)  has  suggested  a  simple,  rapid,  and  exact  method  for  the  analysis  of  calcium 
citrate,  the  content  of  citric  acid  being  obtained  from  the  volume  of  carbon  monoxide  generated 
when  the  citrate  is  heated  with  concentrated  sulphuric  acid.     Two  grams  of  the  citrate,  mois- 
tened in  a  flask  on  the  water-bath,  are  treated  with  25  c.c.  of  concentrated  sulphuric  acid.     By 
means  of  a  current  of  carbon  dioxide,  all  the  carbon  monoxide  is  driven  into  a  nitrometer  similar 
to  that  illustrated  in  Fig.  16  (p.  11),  the  carbon  dioxide  being  absorbed  in  caustic  soda.     Each 
cubic  centimetre   of   CO  at  0°  and  760  mm.  corresponds  with  0-009407  gram   of  citric  acid, 
C6H807  +  H2O;   the  method  cannot  be  used  with  citrate  adulterated  with  oxalate  or  tartrate. 

VOL.  ii.  27 


418 


ORGANIC     CHEMISTRY 


The  output  of  calcium  citrate  in  Sicily  in  1913  was  6000  tons,  besides  800  pipes  of  con- 
centrated juice ;  in  1914  the  output  was  6687  tons,  and  in  1918,  9087  tons  (see  note,  p.  414). 
The  mean  price  fixed  was  £52  per  ton  in  1905,  £80  in  1907,  £50  in  1909,  and  £53  12s.  in 
1910.  In  1909,  owing  to  the  economic  crisis,  exportation  diminished  considerably  and  in 
certain  months  the  price  fell  to  £40  per  ton.  During  the  war  the  sale  price  for  the  citrate 
(64  per  cent.)  was  fixed  at  £280  per  ton  for  the  years  1917-1919. 

The  agro  cotto  exported  in  1905  amounted  to  1200  tons  (£35,520),  and  in  1908  to  750  tons 
(£22,000);  subsequently  practically  only  calcium  citrate  was  exported. 

In  1913,  the  freight  for  calcium  citrate  from  Sicily  to  Marseilles  was  about  10s.  per  ton, 
and  to  London  16s. 

In  1903,  281  works  in  Calabria  and  Sicily  for  the  preparation  of  agro  cotto  employed 
a  total  of  4000  workmen  and  240  h.p. 

The  annual  production  of  refined  citric  acid  in  Europe  was  about  4000  tons  in  1913, 
and  the  price  varied  from  £108  to  £140  per  ton.  In  general  the  price  rises  and  falls  with 
that  of  tartaric  acid,  the  difference  between  the  prices  of  the  two  acids  being  due  to  the 
different  degrees  of  acidity  (3  carboxyls  in  one  case  and  2  in  the  other)  and  molecular 
weights  [152  for  tartaric  acid  and  210  for  citric  acid  (+  H20)]. 

If  all  the  juice  transformed  into  calcium  citrate  for  exportation  were  treated  in  Sicily, 
the  annual  output  would  amount  to  3000  to  4000  tons  of  citric  acid,  which  would  suffice 
to  supply  the  whole  of  Europe. 

The  French  imports  and  exports  are  as  follows  (tons ) : 


Citric  acid 


T  .          (  imported 
Juice 

(exported 


exported 


1913 

134 
31 
29 

452 


1914 

58 

12 

58 

249 


1915  1916 

19  146 

11  131 

37  95 

272  207 


In  the  West  Indies  the  crude  citrus  materials  produced  corresponded  with  1000  tons 
of  calcium  citrate  in  1913  and  with  1200  tons  in  1914. 

The  Argentine  imported  111  tons  of  citric  acid  in  1910  and  208  tons  in  1911. 
For  Germany  the  imports  and  exports  are  as  follows  (tons): 


Imports 
Exports 


1902 

306 
163 


1905 


379 


1909 

193 
358 


1910 

206 
381 


1911 

178 
553 


1912 

162 

550 


1913 

310 
528 


In  addition,  360  tons  of  lemon  juice  were  imported  into  Germany  in  1908  and  170  tons 
in  1909. 

The  import  duty  in  Italy  was  formerly  £4  per  ton,  but  was  raised  in  1909  to  £20  to  protect 
a  large  factory,  with  £40,000  capital,  erected  in  1910-1911  near  Palermo  by  the  firm  of 
Goldenberg ;  during  the  war  this  factory  became  solely  Italian,  with  the  title  Fabbrica 
Chimica  Arenella,  and  it  now  supplies  Italian  needs  and  is  able  to  export  a  considerable 
quantity  of  citric  acid  (see  above). 

In  Austria  there  are  two  citric  acid  factories,  which,  in  1906,  imported  54  tons  of  calcium 
citrate  from  Sicily,  145  from  Turkey,  and  435  from  Greece.  France  has  two  factories, 
these  importing  1811  tons  of  Sicilian  calcium  citrate  in  1906.  In  Germany  there  are  nine 
citric  acid  works  and  four  of  pure  citrates,  1318  tons  of  Sicilian  calcium  citrate  being  imported 
in  1908.  In  England  there  are  ten  works,  almost  all  in  London.  The  United  States  have 
three  very  large  factories  which  produce  more  than  1000  tons  of  citric  acid  and  import  also 
a  certain  quantity  from  Europe,  although  the  protective  duty  is  £31  10s.  per  ton ;  calcium 
citrate,  which  is  all  imported  (in  1911  about  2800  tons,  of  the  value  £160,000),  is  free  from 
duty. 

SALTS  OF  CITRIC  ACID.  Being  tribasic,  this  acid  forms  three  series  of  salts,  as 
well  as  two  different  monosubstituted  acids  and  two  disubstituted  acids.  The  alkali 
salts  are  all  soluble  in  water,  almost  all  of  the  others  being  insoluble,  although  dissolving 
in  alkali  citrates  owing  to  the  formation  of  double  salts;  in  such  solutions,  the  metals 
are  no  longer  precipitable  by  ammonia,  phosphates,  or  alkali  carbonates.  When  heated, 
many  citrates  give  salts  of  aconitic  acid. 

CALCIUM  CITRATE,  (C6H6O7)2Ca3  +  4H2O.  If  calcium  hydroxide  is  added  to  a 
dilute  solution  of  citric  acid,  no  precipitate  forms  in  the  cold  but  one  separates  in  the  hot. 


AMIDES  419 

In  presence  of  ammonia,  calcium  chloride  gives  no  precipitate  in  the  cold,  while  that 
formed  in  the  hot  partly  dissolves  on  cooling  but  does  not  dissolve  in  caustic  soda,  and 
so  differs  from  calcium  tartrate  (see  p.  401).  In  moderately  concentrated  solutions, 
calcium  chloride  precipitates  calcium  citrate,  although  incompletely,  even  in  the  cold; 
in  the  hot,  precipitation  is  complete.  The  water  of  crystallisation  is  wholly  expelled  at 
about  200°. 

Calcium  citrate  is  soluble  in  ammonium  citrate  with  formation  of  a  double  salt 
precipitable  by  alcohol. 

The  manufacture  and  statistics  of  calcium  citrate  are  considered  above. 

BARIUM  CITRATE  is  less  soluble  in  cold  water  than  the  calcium  salt. 

MAGNESIUM  CITRATE,  (C6H5O7)2Mg3,  is  formed  by  dissolving  magnesium  car- 
bonate in  citric  acid  solution.  It  is  used  as  a  purgative  and  is  then  prepared  by  heating 
a  mixture  of  105  parts  of  powdered  citric  acid  with  30  parts  of  magnesium  oxide  cautiously 
at  100°  to  105°,  pouring  the  fused  mass  on  to  porcelain  tiles  and  powdering  when  cold. 
Large  quantities  of  effervescent  magnesia  are  prepared  nowadays  as  a  purgative  and 
refreshing  drink  by  mixing  magnesium  citrate  with  sodium  bicarbonate  and  small  pro- ' 
portions  of  citric  acid  and  sugar,  and  granulating  the  mass  with  addition  of  a  little  glucose. 
Citric  acid  and,  to  some  extent,  magnesium  citrate  are  often  adulterated  with  tartaric 
acid,  which  is  cheaper. 

CITRATE  OF  IRON  is  obtained  as  a  dark  red  colloidal  solution  by  dissolving  ferric 
hydroxide  in  cold  citric  acid  solution.  Such  solutions  of  different  concentrations  give, 
on  heating,  various  citrates  of  iron  which  are  soluble  in  ammonium  citrate  and  more  or 
less  soluble  in  water,  and  have  been  studied  in  recent  years  in  relation  to  their  colloidal 
character. 

Of  the  HIGHER  POLYBASIC  HYDROXY-ACIDS  the  following  may  be  mentioned : 
Desoxalic  acid,  C02H  •  CH(OH)  •  C(OH)(C02H)2,  which  forms  deliquescent  crystals  and, 
when  boiled  with  water,  loses  C02  and  gives  uvic  acid ;  hydroxycilric  acid  (dihydroxytri- 
carballylic  acid),  C3H3(OH)2(C02H)3,  found  in  the  beet;  acetonetricarboxylic  acid  and 
various  acids  which  contain  four,  five,  or  even  more  carboxyl  groups  and  are  of  synthetic 
and  not  of  natural  origin. 

IV.  THIO-ACIDS  AND  THIO-ANHYDRIDES 

These  may  be  regarded  as  acids  or  anhydrides  in  which  an  oxygen  atom  is  replaced  by 
sulphur,  as  in  THIOACETIC  ACID  (Ethanthiolic  Acid),  CH3  •  CO  •  SH,  which  is  obtained 
by  the  action  of  phosphorus  pentasulphide  on  acetic  acid  and  is  a  colourless  liquid  boiling 
below  100°,  giving  an  odour  of  acetic  acid  and  hydrogen  sulphide ;  these  two  compounds 
are  also  formed  by  the  action  of  water  on  the  acid.  ETHANTHIOLTHIOLIC  ACID, 
CH3  •  CS  •  SH,  is  a  dithio-acid,  and  ACETYL  SULPHIDE,  (CH3  •  CO)2S,  a  thio-anhydride. 
The  esters  corresponding  with  these  acids,  e.  g.,  ETHYL  THIOACETATE,  CH3  •  CO  •  SC2H5, 
a  liquid  boiling  unchanged  and  yielding  the  acid  and  mercaptan  on  hydrolysis,  are  also 
known. 

V.  AMIDO-ACIDS,     AMINO-ACIDS,     IMIDES,     AMIDINES,     THIOAMIDES, 
IMINO-ETHERS,   AND  ANALOGOUS   COMPOUNDS 

A.  AMIDO-ACIDS    (AMIDES)   AND   DERIVATIVES 

Like  the  amines  (see  p.  239),  the  amides  may  be  regarded  as  derivatives 
of  ammonia,  the  hydrogen  atoms  of  which  are  replaced,  not  by  alkyl,  but  by 
acid  radicals. 

There  are  thus  primary,  secondary,  and  tertiary  amides,  which  are  obtained 
by  the  replacement  of  one,  two,  or  three  atoms  of  hydrogen,  and  are  sharply 
distinguished  from  the  amines,  as  they  are  readily  hydrolysed  by  alkali,  acid, 
or  superheated  water,  giving  ammonia  and  the  corresponding  acids.  They 
are  generally  crystalline  substances  soluble  in  alcohol  or  ether,  and  the  lower 
members,  especially  of  the  primary  amides,  dissolve  also  in  water.  Their 
boiling-points  are  much  higher  than  those  of  the  corresponding  amines. 

Amides  are  also  known  in  which  one  or  two  atoms  of  the  ammoniacal 


420  ORGANIC     CHEMISTRY 

hydrogen  are  replaced  by  alkyl  radicals,  i.  e.,  alkylated  amides,  e.  g.,  ethyl- 
acetamide  or  acetylethylamine,  CH3  •  CO  •  NH  •  C2H5,  and  dimethylacetamide, 
CH3  •  CO  •  N(CH3)2,  from  which,  on  hydrolysis,  only  the  acid  is  separated,  the 
alkyl  residue  or  residues  remaining  joined  to  the  amino-group,  forming 
non-hydrolysable  amines. 

PREPARATION.  (1)  By  dissolving  an  alkyl  cyanide  (nitrile)  in  con- 
centrated sulphuric  acid,  either  with  or  without  concentrated  acetic  acid, 
concentrated  hydrochloric  acid  or  hydrogen  peroxide,  a  molecule  of  water 
is  added  :  CH3  •  CN  +  H2O  =  CH3  •  CO  •  NH2.  By  heating  acids  or  anhydrides 
with  nitriles,  secondary  or  tertiary  amides  are  formed. 

(2)  The  action  of  ammonia  solution  or  solid  ammonium  carbonate  on 
acid  chlorides  yields  primary  amides,  whilst,  if  the  ammonia  is  replaced  by 
an  amine,  an  alkylated  amide  is  obtained : 

CH3  •  CO  •  Cl  +  2NH3  =  NH4C1  +  CH3  •  CO  •  NH2 
CH3  •  CO  •  Cl  +  2NH2  •  C2H5  =  C2H5  •  NH2,  HC1  +  CH3  •  CO  •  NH  •  C2H5. 

Ethylamine  hydrochloride  Ethylacetamide 

On  the  other  hand,  the  anhydrides  give,  with  ammonia,  the  primary 
anhydride  and  an  ammonium  salt. 

(3)  By  heating  ammonium  salts  of  the  fatty  acids  in  closed  vessels  at 
about  250°,  primary  amides  are  formed  : 

CH3  •  CO2NH4  =  H20  +  CH3  •  CO  •  NH2. 

PROPERTIES.  Unlike  the  amines,  the  amides  have  only  a  very  feeble  basic 
character,  owing  to  the  presence  of  the  negative  acid  radical,  and  only  the 
primary  ones  give  additive  products  with  acids,  e.  g.,  CH3  *  CO  •  NH2,  HC1, 
acetamide  hydrochloride,  which  is  decomposed  even  by  water.  Also  certain 
sodium  and  mercuric  derivatives  are  known,  e.  g.,  (CH3  •  CO -NH)2Hg,  which 
exhibit  the  amides  as  feebly  acid  compounds,  one  of  the  hydrogen  atoms  of 
the  amido-group  being  replaceable  by  metals. 

With  nitrous  acid,  amides  react  similarly  to  primary  amines,  giving  the 
acid  and  liberating  nitrogen : 

CH3  •  CO  •  NH2  +  N02H  =  H20  +  N2  -f  CH3  •  C02H. 

Removal  of  water  from  primary  amides  by  means  of  phosphorus  penta- 
chloride  or  pentoxide  results  in  the  formation  of  alkyl  cyanides  (nitriles). 

By  the  gradual  action  of  bromine  in  presence  of  alkali,  the  corresponding 
amine  with  one  less  carbon  atom  is  finally  obtained,  while  urea  derivatives, 

such  as  methylacetylurea,  CO<-KTTT  .  prr      3,  are  formed  as  intermediate  pro- 

3 

ducts,  these  being  decomposable  by  excess  of  alkali ;  an  intermediate  bromo- 
compound,  e.  g.,  acetobromamide,  CH3  •  CO  •  NHBr,  is  also  formed,  this  giving 
the  amine  with  liberation  of  C02 : 

CH3  -CO  •  NHBr  +  KOH  =  KBr  +  C02  +  CH3  •  NH2. 

When,  however,  the  acid  residue  contains  more  than  five  carbon  atoms, 
the  nitrile  is  obtained  instead  of  the  amine,  which  is  acted  on  by  the  bromine  : 
CBH2n+1  •  CH^  •  NBr2  =  2HBr  +  CBH2n+1  •  CN.  Since  the  nitriles  may  be  con- 
verted into  the  acids  containing  one  less  carbon  atom  than  the  amides  from 
which  they  originate,  it  is  hence  possible  to  pass  gradually  from  higher  acids 
to  more  and  more  simple  ones. 

The  ready  hydrolysability  and  the  methods  of  formation  of  amides  confirm 
their  constitutional  formula,  X  •  CO  '  NH2.  With  the  alkali  salts,  however,  the 
existence  of  the  isomeric  modification,  X  •  C(OH)  :  NH  (see  Tautomerism, 
pp.  18  and  394)  is  assumed,  but  if  the  hydrogen  of  the  hydroxyl  or  amino- 
group  is  replaced  by  an  alkyl  residue,  no  tautomeric  forms  occur,  only  true 


I  HIDES  421 

structural  isomerides,  X  •  CO  •  NHR  and  X  •  C(OR)  :  NH.  The  latter  are  termed 
imino-ethers  and  are  derived  from  the  hypothetical  imino-hydroxides  of  the 
acids,  e.  g.,  CH3*  C(OH)  :  NH.  They  are  prepared  by  the  action  of  a  nitrile 
on  an  alcohol  in  presence  of  gaseous  hydrogen  chloride;  thus,  with  HCN, 
the  hydrochloride  of  formiminic  ether,  CH(OC2H5)  :  NH,  is  obtained  as  a  white 
powder. 

It  is  worthy  of  mention  that  Effront  decomposes  ami  no-acids  on  an 
industrial  scale  by  means  of  special  ferments  so  as  to  obtain  fatty  acids  and 
ammonia  from  them  (see  pp.  183  and  348). 

FORMAMIDE  (Methanamide),  H  •  CO  •  NH2,  prepared  as  described  above,  is  a  liquid 
which  is  soluble  in  water  and  alcohol,  boils  at  200°  with  partial  decomposition,  and  gives 
ammonia  and  carbon  monoxide  when  rapidly  heated ;  with  P2O5  it  yields  HCN,  and  with 
chloral,  an  additive  product,  chloralamide,  which  is  used  as  an  antiseptic  and  hypnotic. 

ACETAMIDE  (Ethanamide),  CH3  •  CO  •  NH2,  forms  needles  melting  at  82°  and  boils 
at  222°.  Diacetyl-derivatives  l  are  obtained  less  easily.  Diacetamide,  (CH3  •  COjgNH,  melts 
at  78°,  boils  at  223°,  and  is  obtained  by  heating  acetamide  with  acetic  anhydride. 

OXAMIC  ACID,  CO2H  •  CO  •  NH2,  is  the  monamide  of  oxalic  acid  and  is  obtained  as  a 
white,  crystalline  powder,  slightly  soluble  in  cold  water,  when  ammonium  oxalate  is  heated. 

OXAMIDE,  NH2  •  CO  •  CO  •  NH2,  is  the  diamide  or  normal  amide  of  oxalic  acid,  and 
is  obtained  by  the  partial  hydrolysis  of  cyanogen  or  by  distillation  of  ammonium  oxalate. 
In  appearance  it  closely  resembles  oxamic  acid  and  it  is  insoluble  in  water  or  alcohol  and  is 
readily  hydrolysed ;  elimination  of  water  (by  P2O5)  from  it  leads  to  cyanogen  (see  p.  240). 

SUCCINAMIC  ACID,  CO2H  •  CH2  •  CH2  •  CO  •  NH2,  is  analogous  to  oxamic  acid,  and 
succinamide,  NH2  •  CO  •  CH2  •  CH2  •  CO-NH2,  is  prepared  similarly  to  oxamide,  to  which  it  is 
analogous ;  succinamide  crystallises  from  water  in  shining  needles,  and  decomposes  at 
200°  into  ammonia  and  succinimide. 

Of  the  amides  of  hydroxy -acids,  only  the  following  need  be  mentioned  : 

GLYCOLLAMIDE,  OH  •  CH2  •  CO  •  NH2,  which  is  obtained  by  treating  the  ester  of 

glycollic  acid  with  ammonia  or,  better,  by  heating  ammonium  tartronate  at  150°,  melts 

at  120°  and  has  a  sweet  taste.    The  diglycollamides,  NH2  •  CO  •  CH2  •  0  •  CH2  •  C02H  and 

(CH2  •  CO  •  NH2)20,  are  also  known,  the  latter,  on  heating,  giving  ammonia  and  diglycol- 

pTT     r*A 

limide,  0<;±2 '  ;C;>NH»  which  melts  at  142°. 
V^HJJ  •  i_/u 

MALIC  ACID,  CO2H  •  CH2  •  CH(OH)  •  CO2H,  forms  two  amides  by  means  of  its  two 
carboxyl  groups,  an  amine  by  means  of  its  alcoholic  group  (aspartic  acid),  and  also  an 
amino-amide  (asparagine ). 

MALAMIC  ACID,  NH2-  CO  •  CH2-  CH(OH)  •  CO2H,  is  known  best  as  its  crystalline 
ethyl  ester,  which  is  formed  by  the  action  of  ammonia  on  an  alcoholic  solution  of  ethyl 
malonate. 

MALAMIDE,  NH2  •  CO  •  CH2  •  CH(OH)  •  CO  •  NH2,  is  formed  by  the  action  of  ammonia 
on  ethyl  malonate  in  the  dry  state. 

B.  IMIDES   AND   IMINO-ETHERS 

Attention  must  be  drawn,  not  so  much  to  the  secondary  amides  [in  which 
two  hydrogen  atoms  of  ammonia  are  replaced  by  two  acid  residues,  as  in 
diacetamide,  (CH3  •  CO)2NH,  which  contains  the  iminic  group,  NH]  or  to  the 

^ 

tautomeric  form  of  the  primary  amides   (with  X  •  Cf  corresponds    the 

XNH2 

1  In  general,  diacelylamines  or  diacylamines  of  the  fatty  or  aromatic  series  are  obtained  by 
one  of  the  following  methods  :  (1)  By  heating  isocyanic  esters  with  acetic  anhydride;  (2)  by 
the  action  of  a  current  of  HC1  in  the  hot  on  the  primary  amides  :  2CH3  •  CO  •  NH2  -f-  HC1  = 
(CH3  •  CO  )2NH  +  NH4C1 ;  part,  however,  undergoes  decomposition :  (CH3  •  CO  )2NH  ±=;  CH3  •  CN  + 
CH3  •  CO.H ;  (3)  from  amines  and  acid  chlorides,  either  with  or  without  pyridine ;  (4)  by  heating 
nitriles  with  acids ;  (5)  by  heating  amines  with  acetic  anhydride  in  a  sealed  tube  at  200° ;  from 
urea  and  acetic  anhydride  in  the  hot,  etc.,  etc. 

The  melting-points  of  some  acylamines  are  as  follows  :  butyramide,  115° ;  dibutyramide,  101° ; 
isobidyramide,  129°;  di-iscbutyramide,  174°;  propionamide,  79°;  dipropionamide,  153°. 


422  ORGANIC     CHEMISTRY 

/OH  /OR 

isomeride  X  •  C^       ,  which  is  well  known  in  the  form  of  imino-ethers,  X  •  C^       , 


/OH 

or,  in  the  case  of  the  imidohydrin  of  glycollic  acid,  OH  •  CH2  •  C^        >  in  the 

XNH 
free  state)  as  to  the  imides  of  certain  dibasic  acids. 

CCK 
OXIMIDE,     |     /NH    (perhaps   with  the  double  formula),  is  formed  on 

ccr 

elimination  of  water  from  oxamic  acid  (by  PC15). 

CH2-C(X 
SUCCINIMIDE,    |  "/NH,  is  obtained  by  heating  succinic  anhydride 

CH2  '  CCT 

in  a  current  of  ammonia  or  by  heating  the  diamide  or  rapidly  distilling  mono- 
ammonium  succinate,  as  has  been  mentioned  on  p.  365,  where  the  reason  was 
given  for  the  ready  formation  of  the  closed-ring  internal  anhydrides. 

Succinimide  melts  at  126°  and  boils  at  288°,  crystallises  with  1H2O  and 
exhibits  the  characters  of  an  acid,  the  iminic  hydrogen,  influenced  by  the  two 
carboxyl  groups,  being  replaceable  by  acids.  On  the  other  hand,  when  they  are 
treated  with  alkali,  these  imides  give  the  amides  from  which  they  originate, 

CH2  •  COv  CH2  •  C02H 

a  molecule  of  water  being  added  :    |  /NH  -f-  H20  =  | 

CH2  •  CW  CH2  •  CO  •  NH2 

It  is  interesting  that,  when  succinimide  is  distilled  over  zinc  dust,  it  yields 

CH  :  CHv 

pyrrole,    \  /NH,  while,  if  it  is  heated  in  alcoholic  solution  with  sodium 

CH  :  CH' 

CH2  •  CH2v 

(reduction),  it  gives  Pyrrolidine,  |  /NH. 

CH2  •  CH2' 

CH2  •  CO, 
Also  Phenylsuccinimide  (Succinanil),    |  /N  '  C6H5,  is  known  and  its 

CH2  •  CO' 

various  transformations  confirm  the  symmetry  of  its  own  structure  and 
consequently  also  that  of  succinimide. 

CH    •  CO 
GLUTARIMIDE,  CH2<££2  .  ^Q>NH,  is  obtained  by  distilling  ammonium 

8 

glutarate  ;  it  melts  at  152°  and  gives  a  little  pyridine  when  heated  with  zinc 
dust. 

C.  AMINO-ACIDS   AND   THEIR   DERIVATIVES 

In  the  amino-acids,  it  is  the  hydrogen  in  direct  union  with  carbon  that  is 
replaced  by  the  NH2-group,  the  carboxyl  group  remaining  intact,  so  that 
these  compounds  have  both  acidic  and  basic  functions,  and  may  hence  be  readily 
separated  from  other  substances,  since  after  the  carboxyl  is  esterified,  salts 
such  as  the  hydrochlorides  of  the  ammo-group  are  formed. 

These  substances  and  their  derivatives  are  of  considerable  importance  in 
animal  and  vegetable  physiology,  since  they  are  found  among  the  products 
of  the  gradual  synthesis  and  decomposition  of  the  proteins  in  the  living 
organism;  they  are  also  of  interest  theoretically,  as  they  form  intermediate 
products  in  various  chemical  syntheses. 

The  a-amino-acids  are  readily  obtained  by  the  action  of  ammonia  on  the 
cyanohydrins  of  ketones  and  aldehydes  and  hydrolysis  of  the  remaining 
nitrile  group  : 


GLYCOCOLL  423 

OH  /NH2 


CN  \CN 

Nifcrile  of  lactic  acid  Nitrilc  of  alanine 

/NH2  /NH2 

CH3  •  C^H      +  2H20  =  NH3  +  CH3  •  C£  H 

XCN  \C02H 

Alanine  (a-Aminopropionic  acid) 

They  are  also  formed  generally  by  reducing  the  oximes  of  ketonic  acids 
or,  better,  by  the  action  of  ammonia  on  halogenated  acids  : 

C02H  •  CH2C1  +  NH3  =  HC1  +  C02H  •  CH2  •  NH2. 

We  may  also  mention  the  interesting  Korner-Meno/zi  reaction  (see  note, 
p.  375),  which  allowed  these  authors,  by  inverting  the  reaction,  to  pass  from 
the  esters  of  unsaturated  acids  (fumaroid  or  maleinoid  form)  to  a  single  form 
of  the  corresponding  saturated  ami  no-acids  by  simple  treatment  with  ammonia 
(or  even  an  alkylamine  in  alcoholic  solution). 

PROPERTIES.  With  nitrous  acid,  the  amino-acids  give  hydroxy-acids 
with  elimination  of  nitrogen,  and  they  give  many  reactions  analogous  to  those 
of  the  hydroxy-acids  and  varying  with  the  position  of  the  amino-group. 

Two  molecules  of  an  a-amino-acid  readily  lose  2  mols.  of  water,  giving  a 
kind  of  anhydride  with  an  imido-ketonic  character  : 

C02H  •  CH2  •  NHa  CO  •  CH2  •  NH 

=  2H20  +  |  | 

NH2  •  CH2  •  C02H  NH  •  CH2  •  CO 

The  y-amino-acids,  however,  give  internal  anhydrides  analogous  to  the 
lactones  and  termed  Lactams  : 

C02H  •  CH2  •  CH2  •  CH2  •  NH2  =  H2O  +  CO  •  CH2  •  CH2  •  CH2 

-  NH 


The  5-amino-acids,  when  heated,  evolve  ammonia  and  give  unsaturated 
acids. 

The  amino-acids  resist  the  action  of  boiling  alkali  solutions,  but  when  fused 
with  caustic  soda  they  yield  the  sodium  salts  of  the  monobasic  acids,  ammonia 
being  liberated.  On  dry  distillation  (best  in  presence  of  baryta)  they  yield 
amines  and  C02,  e.  g,  CH3  •  CH(NH2)  •  C02H  =  CH3  •  CH2  •  NH2  +  C02. 

The  stereoisomerides  may  be  separated  by  means  of  the  strychnine  or 
brucine  salts,  etc. 

GLYCOCOLL  (Glycine,  Aminoacetic  or  Aminoethanoic  Acid,  or  Amine  of  Glycollic 
Acid),  CO2H  •  CH2-  NH2,  is  formed  on  boiling  gelatine  with  alkali  [BafOHJJ  or  acid 
(dilute  H2S04)  or  on  heating  hippuric  acid  (benzoylglycocoll )  with  dilute  acid: 
C02H  *  CH2  •  NH  •  CO  •  C6H5  +  H2O  =  C02H  •  CH2  •  NH2  +  C6H5  •  C02H  (benzoic  acid). 
Synthetically  it  is  obtained  from  monochloracetic  acid  and  concentrated  ammonia  (see 
p.  385);  if  the  ammonia  is  replaced  by  methylamine,  sarcosine,  C02H  •  CH2  •  NH  •  CH3, 
m.-pt.  115°,  is  obtained,  or  if  by  trimethylamine,  betaine  (see  p.  385)  is  formed  : 

C02H  •  CH2C1  +  N(CH3)3  =  HC1  +  CO  •  CH2  •  N(CH3)3. 

O- 

Betaine,  C5HnO2N,  crystallises  with  1H20,  which  it  loses  at  100°  or  in  a  desiccator 
over  sulphuric  acid.  It  dissolves  in  water  or  alcohol,  from  which  it  is  precipitated  by 
ether,  or  as  betaine  hydrochloride  by  hydrochloric  acid.  This  solid  hydrochloride  is  soluble 
in  water,  which  hydrolyses  it  to  a  considerable  extent,  the  solution  then  behaving  like 


424  ORGANIC     CHEMISTRY 

hydrochloric  acid.  Owing  to  this  property  it  is  sold,  under  the  name  of  acidol,  in  pastilles 
containing  exact  and  suitable  doses  for  stomach  complaints,  and  replaces  solutions  of 
hydrochloric  acid  for  this  purpose ;  the  same  effect  as  that  of  the  acid  is  thus  obtained 
by  use  of  a  solid  product.  Betaine  is  a  feeble  base,  and  is  not  decomposed  even  by  boiling 
aqua  regia ;  at  high  temperatures  it  decomposes,  giving  trimethylamine.  It  occurs  abun- 
dantly in  beet-sugar  molasses  (10  to  12  per  cent.,  besides  1  to  2  per  cent,  of  leucine  and 
isoleucine  and  5  to  7  per  cent,  of  glutamic  acid),  from  which  it  is  extracted  by  means  of 
alcohol;  after  evaporation  of  this  solvent,  it  is  separated  as  hydrochloride. 

The  action  of  tertiary  amines,  other  than  trimethylamine,  with  monochloracetic  acid 
gives  various  compounds  to  which  is  given  the  name  of  BETAINES. 

Substitution  in  the  amino -group  of  the  amino -acids  also  yields  other  interesting 
compounds,  e.  g.,  Aceturic  Acid  (acetylglycocoll),  CO2H-CH2-NH-CO-CH3,  melting  at  206°. 

The  properties  of  glycocoll  and  its  salts  are  given  on  p.  385. 

In  the  amino-acid  group  is  also  found  SERINE  or  a-amino-/3-hydroxypropionic  acid, 
CO2H  •  CH(NH2)  •  CH2  •  OH,  which  is  obtained  on  boiling  silk  gelatine  with  dilute  sulphuric 
acid  or  synthetically  from  glycollic  aldehyde,  ammonia,  and  hydrocyanic  acid.  LEUCINE 
(a-aminoisocaproic  acid),  C02H  •  CH(NH2)  •  CH2-  CH(CH3)2,  is  obtained  synthetically  by 
hydrolysing  the  nitrile  of  isovaleraldehyde-ammonia,  and  is  usually  found  with  glycine 
among  the  products  of  decomposition  of  the  proteins  by  acid  or  alkali,  and  is  then  optically 
active  (the  carbon  atom  adjacent  to  the  carboxyl  being  asymmetric). 

ASPARTIC  ACID  (Aminosuccinic  Acid),  C02H  •  CH2  •  CH(NH2)  •  C02H,  is 
one  of  the  most  important  products  obtained  by  the  decomposition  of  proteins 
by  acid  or  alkali.  It  occurs  in  abundance  (Isevo-rotatory)  in  beet-sugar 
molasses,  and  has  been  prepared  by  various  synthetic  methods,  e.  g.,  by  the 
action  of  ammonia  on  bromosuccinic  acid. 

Three  stereoisomerides  are  known,  two  of  them  being  optically  active 
owing  to  the  presence  of  an  asymmetric  carbon  atom.  They  are  obtained  in 
small,  tabular,  dimetric  crystals,  soluble  to  some  extent  in  hot  water.  Their 
cold  solutions  and  also  acid  solutions  of  the  dextro-rotatory  acid  have  a  sweet 
taste,  but  hot  solutions  or  alkaline  solutions  of  the  Isevo-rotatory  acid  are 
without  taste. 

They  give  the  general  reaction  of  amines  and  amides  with  nitrous  acid, 
being  converted  into  malic  acid.1 

The  higher  homologue  of  aspartic  acid  is  Glutamic  Acid  (a-aminoglutaric 
acid),  C02H  •  CH(NH2)  •  CH2  •  CH2  •  CO2H. 

Among  the  DI AMINO- ACIDS  we  have  'Lysine,  CO2H  •  CH(NH2)  •  [CH2]4  •  NH2,  which 
is  obtained  by  the  action  of  acids  on  proteins  or  by  synthetical  methods ;  on  putrefaction 
it  gives  pentamethylenediamine. 

Ornithine,  CO2H  •  CH(NH2)  •  [CH2]3  •  NH2,  is  the  lower  homologue  of  lysine  and  gives 
tetramethylenediamine  (putrescine)  on  putrefaction. 

Taurine  (Ethyleneaminosulphonic  Acid),  S03H  •  CH2  •  CH2  •  NH2,  is  found  in  ox-bile 
combined  with  cholic  acids  as  taurocholic  acid  (for  properties  of  taurine,  see  p.  257 ). 

Cysteine  (Thioserine),  CO2H  •  CH(NH2)- CH2- SH,  is  formed  by  the  reduction  of 
cystine,  CO2H  •  CH(NH2)-  CH2-  S  •  S  •  CH2-  CH(NH2)  •  C02H,  which  occurs  in  urinary 
sediments  (calculi). 

ASPARAGINE,  NH2  •  CO  •  CH2  •  CH(NH2)  •  C02H,  is  the  amide  of  aspartic 
acid.  It  was  first  found  in  asparagus,  but  is  moderately  widespread  in  almost 
all  vegetables  (beet,  potatoes,  beans,  vetches,  peas,  etc.),  especially  during  the 
germination  period,  and  the  dry  seeds  of  certain  lupins  contain  as  much  as 
30  per  cent.  The  constitution  of  asparagine  is  confirmed  by  the  various 
syntheses  leading  to  its.  production. 

1  By  the  action  of  nitrous  acid  on  the  ethyl  ester  of  glycocoll,  Curtius  obtained  Ethyl  Diazo- 

N\ 
acetate,  ||   >CH  •  C02C2H5,  as  a  yellow  oil  with  a  peculiar  odour;  when  heated  it  explodes,  while 

N/ 

with  water  it  loses  nitrogen  and  forms  ethyl  glycollate. 


ASPARAGINE  425 

It  crystallises  with  1H20  in  laevo-hemihedral,  trimetric  prisms,  soluble  in 
hot  water  but  insoluble  in  alcohol  or  ether. 

With  aqueous  cupric  acetate  solution,  it  forms  a  blue,  well-crystallised 
copper  salt,  (C4H703N2)2Cu,  insoluble  in  water.  It  is  isomeric  with  malamide, 
from  which  it  differs  in  the  possession  of  both  acid  and  basic  characters.  It 
is  Isevo-rotatory  and  has  an  unpleasant,  insipid  taste,  but  vetch  seedlings 
contain  a  dextro-rotatory  asparagine  which  has  a  sweet  taste  (Piutti,  1886), 
but  does  not  unite  with  the  laevo-rotatory  form — also  present  in  the  seedlings 
— to  give  the  inactive  modification.  Pasteur  stated  that  the  substance 
composing  the  nerves  of  the  palate  behaves  as  an  optically  active  combination 
which  acts  differently  towards  the  dextro-  and  Isevo-  asparagines. 

Asparagine  is  converted  into  aspartic  acid  by  hydrolysis  and  into  malic 
acid  by  the  action  of  nitrous  acid. 

ASPARTAMIDE,  NH2  •  CO  •  CH2  •  CH(NH2)  •  CO  •  NH2,  is  the  diamide  or 
normal  amide  of  aspartic  acid. 

Numerous  higher  homologues  of  aspartic  acid  (Homo-Aspartic  Acids)  and 
of  asparagine  (Homo-Asparagines)  are  known. 

D.  AMIDO-   AND   IMIDO-CHLORIDES 

With  both  the  primary  amides  and  also  the  alkylated  amides,  the  oxygen  is  readily 
replaced  by  chlorine  by  the  action  of  PC15.  Thus,  acetamide  gives  acetamido-chloride, 
CH3  •  CC12  •  NH2,  and  ethylacetamide,  ethylacetamido-chloride,  CH3  •  CC12  •  NH  •  C2H5.  Both 
of  these  compounds  readily  lose  HC1,  forming  imino-chlorides,  e.  g.,  acetimino.-chloride, 
CH3  •  CC1 :  NH,  and  ethylacetimino-chloride,  CH3  •  CC1 :  N-C2H5.  These  imino-chlorides,  like 
amido-chlorides,  are  readily  decomposed  by  water  into  hydrogen  chloride  and  amide.- 
These  chlorinated  compounds  react  easily  with  aromatic  substances  and  with  hydrogen 
sulphide,  ammonia,  and  amines,  the  chlorine  being  thus  replaced  by  sulphur  or  by  amino- 
residues,  forming  ihioamides,  e.  g.,  CH3  •  CS  •  NHX,  and  amidines,  e.  g.,  CH3  •  C(NH2) :  NX2. 

E.  THIOAMIDES 

These  are  well-crystallised  compounds,  more  acid  in  character  than  the  amides,  and 
hence  capable  of  forming  metallic  derivatives  and  of  dissolving  in  alkali.  Besides  by  the 
reaction  just  mentioned  they  are  obtained  by  the  addition  of  H2S  to  nitriles : 
CH3  •  CN  +  H2S  =  CH3  •  CS  •  NH2  (thioacetamide  or  ethanelhioamide) ;  on  heating,  the 
opposite  change  occurs. 

Phosphorus  pentasulphide  replaces  the  oxygen  of  amides  by  sulphur,  thus  forming 
thioamides.  With  H2S,  isonitriles  give  the  alkylated  thioamides  of  formic  acid, 
CN  •  X  +  H2S  -  H  •  CS  •  NHX. 

Thioamides  are  readily  hydrolysed  (by  alkali,  hot  water,  etc.),  with  formation  of 
H2S,  NH3  (or  amine),  and  the  corresponding  acids  : 

X  •  CS  •  NHX'  +  2H2O  =  X  •  C02H  +  NH2X'  +  H2S. 

F.  IMINOTHIOETHERS 

The  thioamides  (and  especially  their,  derivatives )  can  ex'st  in  the  isomeric  or  tauto- 
meric  form,  X  •  C(SH) :  NH,  in  which  the  hydrogens  of  both  the  sulphydryl  and  theimino- 
group  are  replaceable  by  alkyl  groups,  Iminothioethers,  e.  g.,  X  •  C(SX') :  NH,  being  then 
formed.  These  are  prepared  by  the  action  of  alkyl  iodides  on  the  thioamides  (also  from 
thioalcohols,  nitriles,  and  gaseous  hydrogen  chloride),  e.g.,  CH3  •  CS  •  NH2  +  CH3I  = 

/S  •  CH3 
CH3-  C/  ,  HI  (acetiminothiomethyl  hydriodide). 

>NH 

The  iminothioethers  are  easily  hydrolysed  (by  HC1),  forming  ammonia  and  esters  of 
thio-acids  ; 

/S  •  CH3 
CH3  •  C^  +  H20  =  NH3  +  CH3  -  CO  •  SCH3. 


426  ORGANIC     CHEMISTRY 

G.  AMIDINES 

When  the  amides  or  alkylamides  are  heated  with  amines  in  presence  of  a  dehydrating 
agent  (like  PC13),  the  oxygen  of  the  amide  is  substituted  by  an  imino  -residue  : 

NH 


/ 
<; 
^NR 
NHX' 


X  •  CO  •  NHX'  +  R  •  NH2  =  H2O  +  X 


These  compounds  are  obtained  also  from  thioamides,  isothioamides,  iminochlorides, 
or  iminoethers  by  the  action  of  ammonia  or  of  primary  or  secondary  amines  : 

NH 

CH3  •  CS  •  NH2  +  NH3  =  H2S  +  CH3  •  Cf  (acetamidine  or  ethanamidine). 

\NH2 

NH  NH 

X  •  Cf          +  R  •  NH2  =  X  •  Cf  +  HSX'. 

\SX'  \NHR 

When  nitriles  are  heated  with  the  hydrochlorides  of  primary  (of  the  aromatic  series 
also)  or  secondary  amines  (not  with  NH4C1),  alkylamidines  are  obtained  : 

CH3  •  CN  +  R  •  NH2  =  CH3  •  C( :  NH)-  NHR. 

Properties.  The  amidines  (or  amimides)  are  bases  and  usually  of  the  aromatic 
series;  they  are  easily  hydrolysed  (by  boiling  with  alkali  or  acid),  giving  (when  theiminic 
hydrogen  is  not  replaced  by  an  alkyl  group)  ammonia  (or  an  amine)  andanitrile;  the 
same  change  occurs  on  dry  distillation.  With  H2S  they  give  first  an  additive  product : 

/NHX'; 

X  •  C(  :NH)  -NHX'  +  H2S  =  X  •  C^SH 

NH2 

this    product   then   decomposes   in   two    senses,  giving    (a)  X  •  CS  •  NHX'  +  NH3  and 
(6)  X-CS  •  NH2  +  X' •  NH2. 

With  CS2,  amidines  give  thioamides  and,  at  the  same  time,  thiocyanic  acid  or  an  alkyl 
thiocyanate. 

H.  HYDRAZIDES   AND   AZIDES 

Introduction  of  an  acid  residue  into  hydrazine,  H2N  •  NH2  (see  Vol.  I.,  p.  376),  gives  the 
primary  hydrazides  or  monoacylhydrazides,  e.  g.,  CH3  •  CO  •  NH  •  NH2  (acetylhydrazide)  and 
H-CO-NH-NH2  (formhydrazide,  m.-pt.  54°);  two  acid  radicals  give  secondary  hydrazides 
or  dihydrazides,  e.  g.,  CH3  •  CO  •  NH  •  NH  •  CO  •  CH3  (diacethydrazide,  which  melts  at  138° 
and  is  prepared  from  hydrazine  hydrate  and  acetic  anhydride). 

They  are  readily  hydrolysable,  and  reduce  ammoniacal  silver  nitrate  solution  in  the 
cold  and  Fehling's  solution  on  heating.  The  primary  hydrazides  are  more  highly  basic 
than  the  amides,  and  so  give  more  stable  salts.  Nitrous  acid  acts  on  primary  hydrazides, 
forming  azides,  which  are  derivatives  of  hydrazoic  acid  (see  Vol.  I.,  p.  376) : 

CH,  •  CO  •  NH  -  NH,  +  HNO,  =  2H90  +  CH-  •  CO  •  H/'ll 


These  resemble  the  acichlorides  in  many  properties,  but  are  explosive  (silver  and  lead 
azides,  see  p.  310)  and,  when  heated  with  alcohol,  give  urethanes  and  liberate  nitrogen: 

/N 
CH3  •  CO  •  N<    ||  +  C2H5  •  OH  =  N2  +  CH3  •  NH  •  C02C2H5,  meihylureihane, 

\N 

which  may  be  hydrolysed  with  formation  of  C02,  alcohol,  and  methylamine.  It  is  hence 
possible  to  pass  from  an  acid  to  an  amine  with  one  carbon  atom  less,  by  way  of  the  hydrazide 
and  azide. 


CYANOGEN    COMPOUNDS  427 

I.  HYDROXYLAMINE-DERIVATIVES   OF  ACIDS 

Hydroxylamine  or  its  residues  may  be  united  to  acid  residues,  forming  Hydroximic 
(or  hydroxamic)  Acids,  e.  g.,  CH3  •  C( :  N  •  OH)OH  (ethylhydroxamic  acid,  m.-pt.  59°),  and 
Amidoximes,  X  •  C(  :  N  •  OH)  •  NH2.  The  hydroxamic  acids  have  an  acid  character  and 
are  formed,  with  evolution  of  ammonia,  by  the  action  of  hydroxylamine  on  amides. 

Also  Formyloxime  Chloride,  CH( :  N  •  OH)C1,  is  known,  this  being  obtained  by  treating 
mercury  fulminate  in  the  cold  with  HC1 ;  it  forms  needles,  which  are  readily  decomposable, 
volatile,  and  soluble  in  ether. 

The  Amidoximes  are  formed  by  the  addition  of  nitriles  to  hydroxylamine, 
CH3CN  +  NH2  •  OH  =  CH3  •  C( :  NOH)NH2.  If  hydrogen  cyanide  is  employed,  ISURET 
(Methanamidoxime  or  Methenylamidoxime),  CH(:NOH)NH2,  isomeric  with  urea, 
would  be  obtained. 

VI.  CYANOGEN   COMPOUNDS 

Some  cyanogen  compounds,  especially  Hydrocyanic  Acid,  HCN,  potassium 
cyanide,  and  ferro-  and  ferri -cyanides,  have  already  been  dealt  with  in  Vol.  I., 
pp.  497,  547,  and  840.  We  have  to  consider  here  the  numerous  and  varied 
organic  derivatives  of  cyanogen,  which  are  of  some  interest  as  they  often 
exist  in  polymerised  forms  and  almost  always  in  two  isomeric  modifications, 
sharply  differentiated  by  their  chemical  properties  :  derivatives  of  nitriles, 
X'C  :  N,  and  of  isonitriles,  C  j  N'  X  (see  also  p.  237). 

CYANOGEN,  (CN)2,  is  a  highly  poisonous  gas  with  a  pungent  odour 
recalling  that  of  bitter  almonds ;  it  is  liquid  at  —  21°  and  solid  at  —  34°.  It 
is  found  in  the  gas  from  blast-furnaces  and  occurs  largely  in  the  tail  of  Halley's 
comet,  which  approached  the  earth  in  May  1910.  It  is  obtained  by  the 
elimination  of  water  from  ammonium  oxalate  or  oxamide  (NH2  •  CO  •  CO  •  NH2) 
by  the  action  of  P205  in  the  hot,  or  by  heating  a  solution  of  copper  sulphate 
with  potassium  cyanide,  and  is  commonly  prepared  by  heating  cyanide  of 
silver  or  of  mercury,  Hg(CN)2  =  Hg  -f-  (CN)2 ;  as  a  secondary  product, 
PARACYANOGEN,  (C3N3)2,  or  (CN)W  is  formed  as  a  brown  powder. 

It  burns  with  a  purple  flame,  dissolves  readily  in  alcohol  or  water  (4  :  1), 
and  its  solutions  gradually  become  brown,  with  formation  of  oxalic  acid, 
formic  acid,  hydrocyanic  acid,  ammonia,  and  urea,  and  deposition  of  Azulmic 
Acid  (brown  powder).  With  H2S  it  forms  the  thioamides  :  RUBEANHYDRIC 
ACID,  NH2  •  CS  •  CS  '  NH2,  and  FLAVEANHYDRIC  ACID,  NC  •  CS  •  NH2. 

CYANOGEN  CHLORIDE,  NC  •  Cl,  is  of  importance  in  the  synthesis  of  many  cyanogen 
compounds,  and  is  formed  by  the  action  of  chlorine  on  hydrocyanic  acid  or  metallic  cyanides  : 
NC  •  H  -f-  C12  =  HC1  +  NC  •  Cl.  It  is  a  colourless  gas  which  is  easily  liquefied,  boils  at 
15-5°,  has  a  pungent  odour,  and  dissolves  in  water.  In  presence  of  HC1  it  polymerises, 
forming  CyanogenTrichloride  (melts  at  145°,  boils  at  190° ).  With  KOH  it  forms  potassium 
cyanate,  NCOK. 

CYANIC  ACID,  NC  •  OH,  is  a  liquid  of  penetrating  odour  and  only  slight  stability, 
even  at  the  ordinary  temperature. 

It  is  obtained  by  the  dry  distillation  of  cyanuric  acid  (q.  v. )  and  condensation  of  the 
vapours  in  a  freezing  mixture.  It  undergoes  change,  even  at  the  ordinary  temperature 
and  with  slight  explosions,  into  a  compact,  white  isomeride,  which  is  polymerised  iso- 
cyanic  acid  or  cyamelide,  (0  :  C  :  NH  )x ;  this,  on  dry  distillation,  gives  cyanic  acid  again. 

Its  salts  are  more  stable,  but  when  attempts  are  made  to  liberate  the  acid  from  these 
by  the  action  of  mineral  acids,  immediate  hydrolysis  occurs  : 

NC  •  OH  +  H20  =  CO2  +  NH3. 

If  it  is  liberated  by  dilute  acetic  acid,  the  isomeric  cyanuric  acid  is  obtained. 

The  alkyl  derivatives  of  cyanic  acid  exhibit  two  isomeric  forms :  Cyanates,  N  :  C  •  OX, 
and  Isocyanates,  O  :  C  :  NX. 

Potassium  Cyanate,  NCOK,  forms  white  scales  soluble  in  alcohol  or  water,  and  is 


428  ORGANIC     CHEMISTRY 

obtained  by  oxidising  solutions  of  potassium  cyanide  by  means  of  potassium  perman- 
ganate or  dichromate,  or  by  fusing  potassium  cyanide  or  ferrocyanide  with  PbO,  or  Mn02  • 
NCK  +  0  =  NCOK. 

Ammonium  'Cyanate,  NC-ONH4,  is  isomeric  with,  urea,  into  which  it  can  be  converted. 
It  is  obtained  by  neutralising  cyanic  acid  with  ammonia  and  forms  a  moderately  stable, 
white,  crystalline  mass. 

ETHYL  ISOCYANATE,  CO  :  NC2H5,  is  prepared  by  distillirig  potassium  cyanate 
with  either  potassium  ethyl  sulphate  or  ethyl  iodide.  It  is  a  liquid  of  penetrating  odour 
and  boils  at  60°.  It  does,  not  behave  as  a  true  ester  (true  esters  of  cyanic  acid 
do  not  exist),  since  the  action  of  acid  or  alkali  yields,  not  alcohol,  but  ethylamine; 
CO  :  NC2H5  +  H2O  =  CO2  +  C2H5  •  NH2.  Hence  the  nitrogen  is  united  directly  to  the 
alkyl  group,  so  that  the  structure  is  not  N  •  C  •  OC2H5,  but  O  :  C  :  NC2H5. 

Ethyl  isocyanate  is  instantly  decomposed  by  water,  forming  derivatives  of  urea ; 
the  latter  are  also  formed  by  the  action  of  ammonia  or  amino-bases. 

CYANURIC  ACID,  (NC)3(OH)3,  is  a  polymeride  of  cyanic  acid  and  on  heating  urea 
— which  contains  the  constituents  of  ammonia  and  cyanic  acid — either  alone  or  in  a 
current  of  chlorine  so  as  to  eliminate  the  elements  of  ammonia,  there  remain  those  of 
cyanic  acid,  which  polymerise  to  cyanuric  acid.  It  crystallises  with  2H20  in  prisms, 
effloresces  in  the  air,  and  is  readily  soluble  in  hot  water.  When  heated  with  HC1,  it 
hydrolyses  slowly  to  NH3  and  C02;  with  PC15  it  gives  the  chloride  of  cyanuric  acid. 
It  is  a  tri basic  acid  and  forms  a  violet,  crystalline  copper  salt ;  its  sodium  salt  is  insoluble 
in  concentrated  alkalis.  Like  cyanic  acid,  it  gives  rise  to  two  series  of  derivatives,  e.  g., 
Ethyl  Cyanurate,  (NC)3(OC2H5)3,  which  is  a  colourless  liquid  giving  alcohol  on  hydrolysis. 
It  is  only  slightly  stable,  and  is  readily  transformed  into  the  isomeride  of  the  other  series, 
Ethyl  Isocyanurate,  (CO)3(NC2H5)3,  which  is  formed  by  polymerisation  of  ethyl 
isocyanate,  or  by  distilling  the  cyanurate  with  potassium  ethyl  sulphate.  On  hydrolysis 
it  gives  ethylamine,  this  confirming  its  constitution,  which  is  shown  by  the  following 
closed-ring  formulae  to  be  clearly  different  from  that  of  ethyl  cyanurate. 

0  OC2H5 

/\  /\ 

C2H5-N        N-C2H5  N        N 

O:C          C:O  C2H50  •  C          C-OC2H5 


\N/ 


I  Ethyl  cyanurate 

C2H5 

Ethyl  isocyanurate 

FULMINIC  ACID,  C  :  NOH,  is  readily  volatile  but  unstable,  and  is  decomposed  by 
concentrated  hydrochloric  acid  into  hydroxylamine  and  formic  acid,  chloroformyloxime, 
CHC1 :  N  •  OH,  being  formed  as  intermediate  product.  Kekule  regarded  fulminic  acid 
as  a  nitroacetonitrile,  N02  •  CH2  •  CN,  but  Nef  subsequently  attributed  to  it  the  consti- 
tution C :  N-OH,  the  carbon  being  divalent.  With  bromine,  mercury  fulminate  (see 
p.  308)  gives  the  compound 

Br  •  C  :  N  •  0 

I  I 

Br  •  C  :  N • O 

Silver  fulminate  is  even  more  explosive  than  the  mercury  salt. 

Palazzo  (1907-1910)  has  prepared  various  additive  products  of  fulminic  acid  with 
different  acids  (HBr,  HI,  HSCN,  HNO2,  N3H ).  With  hydrazoic  acid  at  —  12°,  he  obtained 
two  isomerides  with  different  constitutions,  probably  with  intermediate  formation  of 
Triazoformoxime  : 

„  CH N— OH 

N3H  +  C:NOH=tJ>C:N-OH   -— >        || 

3  N  •  N  :  N 

Triazoformoxime  N-hydroxytetrazok  (m.-pt.  145°) 

The  other  isomeride  also  is  possibly  a  tetrazole  derivative. 


THIOCYANIC    ACID 

By  the  action  of  hydrogen  sulphide  on  mercury  fulminate  suspended  in  water,  Cambi 
(1910)  obtained  and  isolated  the  Formothiohydroxamic  Acid  predicted  by  Nef : 

H  •  C : NO • H 

H-S 

FULMINURIC  ACID,  C3H303N3,  is  isomeric  with  cyanuric  acid  (see  above),  and  two 
true  isomerides  are  described:  (1)  a-Isofulminuric  acid,  obtained  in  1884  by  Ehrenberg 
by  treating  mercury  fulminate  suspended  in  ether  first  with  gaseous  hydrogen  chloride  and 
afterwards  with  concentrated  ammonia  solution,  "is  infusible,  and  insoluble  in  water  or 
alcohol,  and  gives  a  deep  red  coloration  with  ferric  chloride;  (2)  (3-isofulminuric  acid, 
obtained  in  1884  by  Scholvien,  melts  at  196°.  Ulpiani  (1912)  maintains  the  existence  of 
only  one  fulminuric  acid,  to  which  he  attributes  the  formula : 

NH2-CO-C 


THIOCYANIC  ACID   AND   ITS   DERIVATIVES 

THIOCYANIC  ACID  (Rhodanic  Acid),  NC  •  SH,  is  a  yellow  liquid  of  penetrating  odour, 
stable  only  when  anhydrous  in  a  freezing  mixture  or  when  in  very  dilute  aqueous  solution. 
At  ordinary  temperatures  it  polymerises  to  a  yellow  mass.  It  is  obtained  from  its  mercury 
salt  (see  later)  by  the  action  of  hydrochloric  acid. 

In  concentrated  aqueous  solution,  it  undergoes  conversion- into  a  yellow  crystalline 
mass  of  Perthiocyanic  Acid,  (CN)2S3H2. 

Cyanogen  Sulphide,  (NC)2S,  may  be  regarded  as  a  kind  of  anhydride  of  thiocyanic 
acid,  and  is  obtained  from  silver  thiocyanate  and  cyanogen  iodide.  It  forms  colourless 
plates  which  have  a  pungent  odour  and  are  readily  soluble  in  water. 

Thiocyanuric  Acid,  (NC)3(SH)3,  is  polymeric  with  thiocyanic  acid,  and  is  obtained 
by  the  action  of  sodium  sulphide  on  cyanogen  chloride.  It  is  a  yellow  powder  and  gives 
salts  corresponding  with  a  tribasic^acid.  Its  trimethyl  salt  is  formed  by  polymerisation 
of  ethyl  thiocyanate  by  heating  at  180°. 

POTASSIUM  THIOCYANATE  (or  Rhodanate),  NC  •  SK,  see  Vol.  I.,  p.  841. 

AMMONIUM  THIOCYANATE  (or  Rhodanate),  NC  •  SNH4,  forms  colourless,  tabular 
crystals  soluble  in  alcohol,  and  readily  so  in  water.  It  is  obtained  by  heating  together 
CS2and  NH3  (see  also  Vol.  I.,  p.  841).  When  heated  it  is  transformed  into  the  isomeric 
thiourea.  It  serves  for  the  preparation  of  other  thiocyanates,  and  is  extracted  in  large 
quantities  from  the  exhausted  Laming  mixture  of  gasworks  (see  p.  49),  which  contains 
1  to  4  per  cent,  of  it. 

MERCURIC  THIOCYANATE,  (NC  •  S)2Hg,  is  prepared  from  a  mercuric  salt  and 
ammonium  thiocyanate,  and  forms  a  white,  insoluble  powder  which  swells  up  to  a  very 
considerable  extent  when  heated  (Pharaotis  serpents). 

SILVER  THIOCYANATE  is  precipitated  as  a  white  mass  on  mixing  silver  nitrate 
and  ammonium  thiocyanate.  The  latter  gives,  with  ferric  salts,  a  dark  red  coloration 
of  FERRIC  THIOCYANATE  (sensitive  indicator  in  the  titration  of  silver  with  thio- 
cyanate) and  this,  with  potassium  thiocyanate,  gives  a  violet  double  salt,  (NC  •  S)6FeK3. 

Hydrogen  sulphide  decomposes  the  thiocyanates,  NC  •  SH  +  H2S  =  NH3  +  CS2, 
while  with  concentrated  sulphuric  acid,  addition  of  water  and  decomposition  into  ammonia 
and  carbon  oxysulphide  occur 

NC  •  SH  +  H20  =  COS  +  NH3. 

For  thiocyanic  acid  there  are  two  series  of  isomeric  derivatives,  corresponding  with 
the  two  general  formulae  :  N  :  C  •  SX  (alkyl  thiocyanate)  and  S  :  C  :  N  •  X  (mustard  oils). 

ETHYL  THIOCYANATE,  NC  •  SC2H5,  is  a  colourless  liquid  with  a  marked  odour  of 
garlic ;  it  boils  at  142°  and  is  very  slightly  soluble  in  water.  It  is  formed  by  the  action 
of  cyanogen  chloride  on  mercaptides,  or  by  distillation  of  potassium  thiocyanate  with 
potassium  ethyl  sulphate.  As  it  has  the  constitution  of  a  true  ester,  it  is  hydrolysed 
by  alcoholic  potash  with  formation  of  alcohol  and  potassium  thiocyanate,  but  in  certain 


430  ORGANIC     CHEMISTRY 

reactions  it  behaves  like  the  isomeric  mustard  oils.  Nascent  hydrogen  converts  it  into 
mercaptan,  since  the  alkyl  is  united  to  sulphur,  and  the  action  of  nitric  acid  in  the  hot 
yields  ethylsulphonic  acid. 

ALLYL  THIOCYANATE,  NC  •  SC3H5,  boils  at  161°,  and  has  a  garlic-like  odour; 
it  undergoes  change  into  the  isomeric  mustard  oil,  slowly  at  the  ordinary  temperature 
and  more  rapidly  on  distillation. 

The  Mustard  Oils  (Isothiocyanates)  are  obtained  from  the  corresponding 
thiocyanates  simply  by  heating.  They  are  also  formed  by  the  action  of 
carbon  disulphide  on  the  corresponding  primary  amines,  CS2  -f-  X  *  NH2  = 
H2S  +  S  :  C  :  NX,  this  change  taking  place  by  way  of  the  intermediate 
alkylamine  salt  of  alkyldithiocarbamic  acid  (see  later],  which  is  distilled  with 
mercuric  chloride.  Mustard  oils  are  formed  also  when  an  alkylated  thiourea 
is  distilled  with  phosphoric  or  concentrated  hydrochloric  acid. 

Their  structure  is  indicated  by  their  formation  of  primary  amine  on  hydro- 
lysis :— S  : C : NX  +  2H20  =  C02  +  H2S  +  X  •  NH2.  The  isothiocyanic  acid, 
S  :  C :  NH,  from  which  these  mustard  oils  are  regarded  as  derived,  is  not 
known  in  the  free  state. 

METHYL  MUSTARD  OIL  (Methyl  Isothiocyanate),  SC  :  NCH3,  melting  at  34°  and 
boiling  at  119°;  Ethyl  Mustard  Oil,  SC :  NC2H5,  boiling  at  134°;  and  Propyl  Mustard 
Oil,  SC  :  NC3H7,  boiling  at  153°,  are  of  little  importance.  More  interesting  is 

ALLYL  MUSTARD  OIL  (or  Ordinary  Mustard  Oil  ;  Allyl  Isothiocyanate), 
S  :  C  :  NC3H5,  which  is  prepared  by  distilling  Sinapis  nigra  (black  mustard )  with  water ; 
it  is  obtained  synthetically  by  the  reactions  given  above.  It  is  a  liquid  with  a  pungent 
odour  recalling  that  of  mustard  and  raises  blisters  on  the  skin ;  it  is  sparingly  soluble  in 
water  and  boils  at  150-7°. 

CYANAMIDE  AND   ITS   DERIVATIVES 

CYANAMIDE,  NC  •  NH2,  is  a  white  crystalline  substance,  melting  at  40° 
and  dissolving  very  slightly  in  water,  alcohol,  or  ether.  It  is  obtained  by 
passing  a  current  of  cyanogen  chloride  into  an  ethereal  solution  of  ammonia : 
2NH3  +  NC  •  Cl  =  NH4C1  +  NC  •  NH2,  and  is  also  formed  by  desulphurising 
thiourea,  NH2  •  CS  *  NH2,  by  means  of  HgO,  which  removes  H2S. 

It  is  obtained  abundantly  and  in  a  pure  state  by  extracting  calcium 
cyanamide  (see  later)  systematically  with  water,  neutralising  the  saturated 
solution  with  sulphuric  acid,  filtering  from  the  calcium  sulphate,  concen- 
trating in  a  vacuum,  again  filtering  from  the  gypsum,  concentrating  anew, 
and  extracting  the  crystalline  mass — formed  on  cooling — with  ether,  which 
does  not  dissolve  gypsum,  dicyanamide,  and  other  impurities.  Evaporation 
of  the  ether  yields  pure  cyanamide  in  almost  theoretical  yield  (Baum,  1910). 

With  lapse  of  time,  or  rapidly  at  150°,  cyanamide  changes  into  the  poly- 
meric dicyanodiamide  '(see  later).  It  behaves  both  as  a  weak  base  forming 
unstable  crystalline  salts  and  as  a  weak  acid  giving  metallic  salts,  e.g., 
NC  •  NHNa,  NC  •  NAg2,  etc.  The  most  important  of  these  is  calcium  cyan- 
amide,  NC  •  NCa,  which  was  considered  in  detail  in  Vol.  I,  pp.  369  et  seq.,  in 
the  discussion  of  the  utilisation  of  atmospheric  nitrogen;  it  is  formed  by  the 
action  of  nitrogen  on  heated  calcium  carbide  and  forms  an  excellent  nitrogenous 
fertiliser. 

In  presence  of  dilute  acid,  cyanamide  fixes  a  molecule  of  water,  giving 
urea  :  NC  •  NH2  +  H20  =  NH2  •  CO  •  NH2 ;'  with  hydrogen  sulphide  it  yields 
thiourea.  Cyanamide  also  gives  two  series  of  isomeric  alkyl  derivatives  of 
the  general  formulae,  N  |  C  *  NX2  and  XN  :  C  :  NX.  Compounds  of  the  latter 
formula  are  derived  from  the  hypothetical  carbodi-imide,  NH  :  C  :  NH ;  for 
example,  carbodiphenylimide,  C6H5N :  C :  NC6H5,  boiling  at  330°,  is  well 
characterised. 


CARBONIC    ACID    DERIVATIVES  431 

DIETHYLCYANAMIDE,  NC  •  N(C2H5)2,  is  formed  by  the  action  of  ethyl  iodide 
on  the  silver  salt  of  cyanamide,  its  structure  being  indicated  by  the  products — 
CO2+ NH3+ NH(C2H5)2 — obtained  on  hydrolysis  with  dilute  acid.  Methyl-  and 
elhyl-cyanamide  are  also  known. 

DICYANODIAMIDE,  (NC  •  NH2)2,  is  formed,  as  has  already  been  mentioned,  from 

.NH 
cyanamide ;  certain  of  its  reactions  indicate  the  structure  NC  •  NH  •  Cf  (Bamberger ). 

\NH2 

It  forms  acicular  crystals  or  small  flat  prisms.  When  heated  strongly  and  rapidly,  it  is 
converted  into  a  white  insoluble  powder,  MELAM,  C6H9NU  or  [(NC^NH^jgNH,  this 
being  an  imide  of  melamine,  into  which  it  is  transformed  by  sulphuric  acid  or  ammonia. 

MELAMINE  (Cyanurtriamide),  (NC)3(NH2)3,  is  a  crystalline  basic  substance,  insoluble 
in  alcohol  or  ether.  When  it  is  boiled  with  acid,  the  amino-groups  are  gradually  replaced 
by  hydroxyl  groups,  giving  AMMELINE,  (NC)3(NH2)2OH,  then  AMMELIDE, 
(NC)3NH2(OH)2,  and  finally  Cyanuric  Acid,  (NC)3(OH)3. 

As  usual,  the  alkyl  derivatives  form  two  isomeric  series,  derivatives  being  known  of  a 
hypothetical  Isomelamine,  (CNH)3(NH)3,  among  these  being  the  polymerised  alkyl- 
cyanamides. 

VII.  DERIVATIVES  OF  CARBONIC  ACID 

True  carbonic  acid,  O :  C(OH)2,  is  not  known  in  the  free  state,  since  two 
hydroxyl  groups  cannot  exist  in  combination  with  the  same  carbon  atom 
(see  p.  216),  but  it  is  supposed  to  exist  in  aqueous  solution,  and  salts  corre- 
sponding with  this  formula  are  stable  and  well  known  (carbonates  and  bicar- 
bonates).  Also  important  organic  derivatives,  similar  to  those  already  studied 
for  other  dibasic  acids  (amides,  chlorides,  esters,  etc.),  are  known.  The  acid 
derivatives  are  less  stable  than  the  normal  ones. 

ESTERS   OF  CARBONIC  ACID 

ETHYL  CARBONATE,  CO(OC2H5)2,  is  a  liquid  which  is  insoluble  in  water,  boils  at 
126°,  and  has  a  pleasant  odour.  It  is  formed  by  the  interaction  of  ethyl  chlorocarbonate 
and  alcohol :  C2H5  •  OH  +  Cl  •  CO  •  OC2H5  =  HC1  +  CO(OC2H5)2,  and  also  from  silver 
carbonate  and  ethyl  iodide.  Mixed  esters,  containing  different  alkyls,  also  exist. 

ETHYLCARBONIC  ACID,  CO(OH)  •  OC2H5,  is  known  only  as  salts,  e.g.,  Potassium 
Ethylcarbonate,  CO  (OK)  •  OC2H5,  which  is  obtained  by  the  action  of  C02on  an  alcoholic 
solution  of  potassium  ethoxide  and  forms  shining  scales,  giving  alcohol  and  potassium 
carbonate  when  treated  with  water. 

CHLORIDES   OF  CARBONIC  ACID 

Carbon  Oxychloride  (phosgene),  COC12,  has  already  been  described  (Vol.  I.,  p.  492). 

CHLOROCARBONIC  ACID,  COC1  •  OH,  is  the  acid  chloride  of  carbonic  acid,  but 
is  not  stable,  and,  when  liberated,  decomposes  into  C02  and  HC1.  Its  esters  are,  however, 
well  known,  the  action  of  phosgene  on  absolute  alcohol  giving,  for  example,  ethyl  chloro- 
carbonate (Ethyl  Chloroformate),  Cl  •  CO  •  OC2H5,  thus  :  C2H6  •  OH  +  COC12  =  HC1  + 
Cl  •  CO  •  OC2H5. 

This  ester  is  a  liquid,  having  a  pungent  odour,  boiling  at  93°  and  readily  decomposing 
under  the  action  of  water ;  it  is  used  largely  in  organic  syntheses  to  introduce  carboxyl 
into  the  molecule. 

AMIDES   OF  CARBONIC   ACID 

The  acid  amide,  NH2  •  CO  •  OH,  is  Carbamic  Acid,  and  the  normal  amide,  NH2  •  CO 
NH,,  urea. 

CARBAMIC  or  CARBAMINIC  ACID,  NH2  •  CO  •  OH,  is  obtained  as  ammonium  salt 
— ammonium  carbamate,  NH2  •  CO  •  ONH4 — by  the  direct  union  of  dry  CO2  and  NH3 ; 
a  white  mass  is  thus  obtained  which,  even  at  60°,  dissociates  into  C02  +  NH3.  In  aqueous 
solution  this  salt  does  not  precipitate  solutions  of  calcium  salts  at  the  ordinary  tem- 
perature, since  calcium  carbamate  is  soluble,  but  in  the  hot  the  salt  decomposes  into  C02 
and  NH3  and  gives  a  precipitate  of  calcium  carbonate. 


432  ORGANIC     CHEMISTRY 

Ethyl  carbamate  or  URETHANE,  NH2  •  CO  •  OC2H5,  is  also  well  known  and  is 
obtained  by  the  action  of  ammonia  on  ethyl  carbonate,  CO  (OC2H5  )2  +  NH3  =  C2H5  •  OH  + 
NH2  •  CO  •  OC2H5,  or,  more  easily,  by  treating  ethyl  chlorocarbonate  with  ammonia  : 


COC1(OC2H5)  +  2NH3  -  NH4C1  +  NH2  •  CO 

It  melts  at  48°  to  50°,  is  soluble  in  water,  and  is  used  as  a  soporific. 

The  following  are  also  known  :  iodourethane,  NHI  •  CO  •  OC2H5  ;  ethylur  ethane, 
NHC2H5  •  CO  •  OC2H5  (boils  at  175°);  nitrourethane,  NO2  •  NH  •  CO  •  OC2H5;  carbamidyl 
chloride,  NH2  •  CO  •  Cl  (melts  at  50°  and  boils  at  61°);  and  diethyl  iminodicarbonate, 
NH(CO  •  OC2H5)2,  which  is  the  imide  of  urethane. 

Urethane  derivatives  are  readily  hydrolysable  with  alkalis  and  yield  ammonia  and 
urea  when  heated. 

UREA  (Carbamide),  CO(NH2)2,  is  the  final  oxidation  product  of  nitrogenous  com- 
pounds in  the  living  organism,  and  the  adult  human  being  produces  about  30  grams  of 
it  a  day  ;  it  is  found  in  general  in  the  urine  of  carni  vora  (where  it  was  first  discovered  ) 
and  in  other  animal  fluids.  It  crystallises  in  shining  needles  soluble  in  water  and  in 
alcohol,  but  insoluble  in  ether  ;  it  melts  at  132°  and  sublimes  in  a  vacuum.  It  is  formed 
from  ammonium  cyanate  by  simple  rearrangement  under  the  action  of  heat  (Wohler): 
NC  •  ONH4  =  CO(NH2)2.  Escales  (1911)  found  that  when  urea  is  distilled  or  sublimed 
in  a  vacuum,  the  reverse  reaction,  i.  e.,  formation  of  ammonium  cyanate,  occurs,  Urea 
is  obtained  also  by  the  action  of  ammonia  on  ethyl  carbonate  or  carbamic  acid  : 

CO(OC2H5)2  +  2NH3  =  2C2H5  •  OH  +  CO(NH2)2. 

Many  other  reactions  give  urea,  e.  g.,  oxidation  of  thiourea,  action  of  water  on  cyanamide, 
best  in  the  cold  and  in  presence  of  hydrated  manganese  peroxide  as  catalyst  (Ger.  Pat. 
254,474,  1910  ;  U.S.  Pat.  796,713)  ;  it  may  also  be  prepared  from  COCl2and  NH3,  etc.  In 
the  laboratory  it  is  prepared  by  treating  with  barium  carbonate  the  urea  nitrate  obtained 
by  evaporating  urine  in  presence  of  nitric  acid,  or  by  heating  ammonium  sulphate  solution 
with  potassium  ferro  cyanide  or  cyanate  : 

(NH4)2S04  +  2NCOK  =  K2S04  +  2CO(NH2)2. 

In  the  future  urea  will  probably  be  prepared  on  an  enormous  industrial  scale  according 
to  the  scheme  of  the  Badische  Anilin-und  Soda-Fabrik  of  Ludwigshafen  and  Oppau. 
Synthetic  ammonia  is  obtainable  by  the  Haber  process  (see  Vol.  I.,  p.  373),  and  an  abun- 
dant supply  of  CO2is  obtained  in  the  preparation  from  water-gas  of  the  hydrogen  necessary 
for  the  synthesis  of  ammonia.  Thus  ammonium  sulphate  may  be  made  economically 
according  to  the  reaction,  NH3  +  C02  +  H2O  +  CaS04  ==  CaC03  +  (NH4)2S04,  and 
urea  from  C02  and  NH3  in  an  autoclave  :  CO2  +  2NH3  =  H20  +  CO(NH2)2.  Since  urea 
contains  more  than  46  per  cent,  of  nitrogen,  its  use  as  a  high-grade  nitrogenous  fertiliser 
is  anticipated  when  it  can  be  manufactured  to  compete  with  other  fertilisers. 

When  heated  it  is  decomposed  into  ammonia,  biuret  (see  later),  cyanuric  acid,  and 
ammelide.  It  is  readily  hydrolysed  by  acids,  alkalis,  or  even  hot  water  :  CO(NH2)2  + 
H20  =  C02  +  2NH3,  and  is  decomposed  by  nitrous  acid  or  sodium  hypochlorite  : 

2HN02  +  CO(NH2)2  =  3H20  +  C02  +  2N2. 

Owing  to  this  property  urea  is  used  as  a  stabiliser  (so-called  !)  for  explosives,  decom- 
position being  retarded  and  the  nitrous  vapours  fixed  (see  p.  303  ). 

It  exhibits  the  properties  of  a  base  and  of  a  weak  acid,  giving  salts  with  acids  (e.  g., 
Urea  Nitrate,  CO(NH2)2,  HN03,  which  is  soluble  in  water  and  slightly  so  in  nitric  acid, 
and  with  concentrated  sulphuric  acid  gives  the  highly  acid  Nitrourea,  NH2  •  CO  •  NH  • 
NO2,  and  with  bases,  e.  g.,  CO(NH2)2,  2HgO.  It  also  crystallises  with  other  salts,  e.  g., 
CO(NH2),  +  NaCl  +  H2O,  CO(NH2)2  +  AgNO3,  etc.  Mercuric  nitrate  precipitates  urea 
quantitatively  from  its  neutral  aqueous  solutions  as  2CO(NH2)2  +  Hg(NO3)2  +  3HgO. 

Urea  forms  various  alkyl  derivatives;  thus  ethyl  cyanate  and  ethylamine  give  symm. 
or  a-diethylurea,  which  is  isomeric  with  unsymm.  or  /3-diethylurea,  NH2  •  CO  •  N(C2H5)2; 
CO  •  NC2H5  +  C2H5  •  NH2  =  CO(NHC2H5)2.  The  constitutions  of  these  alkyl  derivatives 
are  determined  by  study  of  the  products  of  their  hydrolysis. 

NH 

Readily  hydrolysable  alkylisoureas,  NH  :  C<^~vV2,  are  also  known. 


THIOCARBONIC    ACID    DERIVATIVES      433 

SEMICARBAZIDE,  NH2  •  CO  •  NH  •  NH2,  which  is  obtained  from  potassium  cyanate 
and  hydrazine  hydrate,  may  also  be  regarded  as  a  derivative  of  urea.  It  has  already 
been  seen  that  this  base  (which  melts  at  96°)  gives  crystalline  compounds  (semicarbazones) 
with  ketones  and  aldehydes  (see  p.  246 ).  CARBAZIDE  (Carbohydrazide),  CO(NH  •  NH2)2, 
melts  at  152°,  and  is  obtained  from  esters  of  carbonic  acid  by  the  action  of  hydrazine 
hydrate. 

Acetylurea,  NH2  •  CO  •  NH  •  CO  •  CH3,  and  Allophanic  Acid,  NH2  •  CO  •  NH  •  CO^ 
(not  known  free,  but  as  salts ),  are  obtained  from  acid  chlorides  and  urea. 

The  formation  of  ureides  (compounds  of  urea  and  mono-  and  dibasic  acids)  takes 
place  with  monobasic  divalent  acids  or  with  an  alcohol  and  acid.  Such  a  reaction  gives 
Hydantoic  Acid  (glycoluric  acid),  NH2  •  CO  •  NH  •  CH2  •  C02H,  which,  when  evaporated  in 

,NH  •  CO 
presence  of  HC1,  loses  water  and  forms  Hydantoin,  CO^  |       ,  the  latter  giving  first 

\NH  •  CHS 
hydantoic  acid  and  then  C02,  NH3,  and  glycine  on  hydrolysis. 

When  urea   is    heated  at  160°,  2  mols.  condense  with  separation  of   ammonia   and 

/CO  •  NH, 

/ 
formation  of  Biuret,  NH<^  ,  which  crystallises  with  1H2O  and  is  soluble  in  water 

\nr>  .  -\TTT 

\^\J  '  -LNXTo 

or  alcohol ;    in  alkaline  solution  it  gives  a  characteristic  violet  coloration  with  a  little 
copper  sulphate. 

DERIVATIVES   OF   THIOCARBONIC   ACID 

More  or  less  complete  substitution  of  the  oxygen  of  carbonic  acid  by 
sulphur  gives  a  series  of  unstable  compounds,  which  form  stable  alkyl  deriva- 
tives and  exhibit  various  cases  of  isomerism  indicated  by  varying  products 
of  hydrotysis.  These  numerous  sulphur  compounds  are  reducible  to  three 
types,  according  as  they  contain  (1)  the  nucleus  SC<C,  thiocarbonic  or  thio- 
carbamic  compounds,  (2)  the  nucleus  OC<C,  carbonyl  or  carbamic  compounds, 
or  (3)  the  group  H  •  N :  C<C,  iminocarbonic  or  iminocarbamic  compounds. 

The  following  are  the  principal  compounds  of  these  types,  which  have  been  thoroughly 
studied  in  the  form  of  their  alkyl  derivatives  : 


Trithiocarbonic  acid  .          .     SC(SH)2 


Dithiocarbonic  acid 


Monothiocarbonic  acid       .          .     SC< 


Dithiocarbamic  acid 


OH 
OH 


Dithiocarbonylic  acid        .          .       CO(SH)2 

OTT 

Monothiocarbonylic  acid  .          .    CO-e^L,^ 


Monothiocarbonylamic  acid 


NH 

Monothiocarbamic  acid     .          .     SC<n w  2 


Thiocarbamide          .          .         .     SC< 


NH2 
NH2 

Thiophosgene.          .          .          .          SC :  C12 

TVTTT 

Thiocarbamidyl  chloride  . 
Iminodithiocarbonic  acid  HN:C(SH)2 

QTT 

Iminomonothiocarbonic  acid    HN :  C-^^TT 

Uli 

NH 

Iminothiocarbamic  acid    .        HN  :  C^^ 


THIOPHOSGENE  (Carbon  Sulphochloride),  SCC12,  is  a  red  liquid  which  fumes  in  the 
air,  attacks  the  mucous  membrane,  and  boils  at  68°  to  74°.  It  is  prepared  by  the  action 
of  chlorine  on  carbon  disulphide,  the  intermed  ate  compound,  CC13  •  SCI,  thus  obtained 
being  reduced  with  stannous  chloride.  It  is  more  stable  towards  water  than  phosgene, 
and  with  ammonia  gives,  not  thiourea,  but  ammonium  thiocyanate. 

TRITHIOCARBONIC  ACID,  CS3H2,  is  obtained  as  sodium  salt  by  the  action  of 
carbon  disulphide  on  sodium  sulphide.  The  free  acid  is  a  brown  unstable  oil  and  its  ethyl 
ester,  SC(SC2H5)a,  a  liquid  boiling  at  240°. 

POTASSIUM  XANTHATE,  KS  •  SC  •  OC2H5,  is  the  ether  of  the  potassium  salt  of 
dithiocarbonic  acid.     It  is  formed  by  the  action  of  CS2  on  C2H5  •  OK  and  crystallises  in 
shining  needles  soluble  in  water  and  to  a  less  extent  in  alcohol.     With  copper  sulphate  it 
gives  copper  xanthate  as  an  unstable  yellow  powder  which  is  used  in  indigo  printing. 
VOL.  n.  28 


434  ORGANIC     CHEMISTRY 

XANTHIC  or  XANTHONIC  ACID,  HS  •  SC  •  OC2H5,  is  liberated  from  its  potassium 
salt  (see  above)  and  forms  an  oil  insoluble  in  water;  it  readily  decomposes  into 
C2H5  •  OH  +  CS2. 

,  DITHIOCARBAMIC  ACID,  NH2  •  SC  •  SH,  is  obtained  as  ammonium  salt  by  the 
action  of  ammonia  on  an  alcoholic  solution  of  CS2: 

2NH3  +  CS2  =  NH2  •  SC  •  SNH4. 

In  the  free  state  this  acid  forms  an  unstable,  reddish  oil  (decomposing  into  SH2  + 
thiocyanic  acid )  and  its  ethyl  ester,  NH2  •  SC  •  SC2H5,  is  dithiourethane,  whilst  ihiourethane 
will  be  NH2  •  CO  •  SC2H5  and  is  isomeric  with  xanthogenamide,  NH2  •  CS  •  OC2H5. 

Ethylamine  Ethyldithiocarbamate,  C2H5  •  NH  •  SC  •  SH,  NH2-  C2H5,  is  formed  similarly 
by  the  action  of  carbon  disulphide  on  ethylamine;  in  the  hot  it  gives  diethylthiourea, 
SC(NHC2H6)2,  the  mercuric  salt  of  which  gives  the  corresponding  mustard  oil  with  water 
in  the  hot,  whilst  the  alkylated  dithiocarbamic  acids  obtained  with  secondary  amines 
do  not  give  mustard  oils  under  these  conditions. 

THIOCARBAMIDE  (Thiourea),  SC(NH2)2,  is  only  partly  obtained  on  heating 
ammonium  thiocyanate  at  130°,  the  reaction  being  reversible.  It  forms  crystals  melting 
at  172°,  and  dissolving  in  water  and  in  alcohol,  giving  neutral  solutions;  it  has  a  bitter 
taste.  On  hydrolysis  it  yields  C02  +  H2S  -f  NH3.  As  has  already  been  stated,  it  is 
converted  into  urea  by  permanganate,  into  cyanamide  by  mercuric  oxide,  and  into 
potassium  thiocyanate  and  ammonia  by  alcoholic  potash  at  100°.  It  behaves  as  a  weak 
acid  and  a  weak  base,  and  its  derivatives,  in  some  cases,  correspond  with  the  tautomeric 

NH 
formula,  HNC<ToTT  2  (hypothetical  iminothiocarbamic  acid). 

oil 

About  10,000  kilos  of  thiourea  are  produced  annually  by  two  factories,  one  French 
and  the  other  German,  for  preserving  weighted  silk  from  corrosion,  the  Gianoli  process 
(see  later,  under  Silk)  being  used.  Owing  to  this,  the  price  of  thiourea  was  lowered  in 
pre-war  times  from  £2  to  5s.  6d.  or  Qs.  6d.  per  kilo. 

GUANIDINE   AND   ITS   DERIVATIVES 

NH 
GUANIDINE  (Iminourea  or  Iminocarbamide),  NH  :  C<NjT2,  forms  crystals 

2 

readily  soluble  in  water  or  alcohol.  It  is  a  strong  base,  absorbing  carbon 
dioxide  from  the  air,  but  is  converted  into  salts  by  one  equivalent  of  acid. 
The  fatty  acid  salts  are  converted  on  heating  into  guanamines,  which  form 
crystals  of  peculiar  shape. 

It  is  obtained  by  heating  cyanamide  with  ammonium  iodide  :  NH4I  + 
CN  •  NH2  =  NH  :  C(NH2)2,  HI ;  or,  better,  as  thiocyanate  by  heating  thiourea 
with  ammonium  thiocyanate  at  190°  : 

NCS  •  NH4  +  SC(NH2)2  =  H2S  +  NH  :  C(NH2)2,  NC  •  SH. 

It  may  also  be  obtained  from  dicyanodiamide  by  the  action  of  aqua  regia 
(Ulpiani,  1907). 

Guanidine  is  readily  hydrolysed,  forming  first  ammonia  and  urea  and 
then  CO2  and  NH3. 

Guanidine  Nitrate,  NH:C(NH2)2,  HN03,  is  converted  by  concentrated  sulphuric 
acid  into  nitroguanidine,  NH  :  C(NH2)(NH  •  N02),  and  this,  on  reduction,  gives  amino- 
guanidine,  NH  :  C(NH2)(NH  •  NH2).  The  latter  gives  hydrazine  [(NH2)2],  NH3,  and  C02 
on  hydrolysis  with  acid  or  alkali,  whilst  with  nitrous  acid  it  yields  Diazoguanidine  (imino- 
carbamideazide),  NH :  C(NH2)  •  N3,  which  is  resolved  by  alkali  into  hydrazoic  acid  (see 
Vol.  L,  p.  376)  and  cyanamide. 

From  aminoguanidine  can  be  obtained  Azodicarbonamide,  NH2  •  CO  •  N :  N  •  CO  •  NH2, 
and  Hydrazodicarbonamide,  NH2  •  CO  •  NH  •  NH  •  CO  •  NH2. 

GLYCOCYAMINE,  NH  :  C(NH2)  •  NH  •  CH2  •  CO2H,  is  formed  by  the  union  of  glycocoll 


URIC    ACID    GROUP  435 

xNH   CO 

with  cyanamide,  and  if  water  is  lost  Glycocyamidine,  NH  :  C<^  |  ,  is  obtained.   If, 

XNH  •  CH2 

however,  instead  of  glycocoll,  its  methyl-derivative  is  taken,  sarcosine,  CO2H  •  CH2  • 
NH  •  CH3  (melts  at  115°  and  is  neutral),  results,  creatine  and  creatinine  being  obtained 
similarly. 

CREATINE,  NH  :  C(NH2)  •  N(CH3)  •  CH2  •  CO2H,  is  obtained  from  meat-extract,  being 
a  stable  component  of  muscle.  It  has  a  neutral  reaction  and  is  soluble  in  water  and 
sparingly  so  in  alcohol  ;  it  crystallises  with  1H2O,  has  a  bitter  taste  and,  when  heated 
with  acid,  loses  1  mol.  of  water  of  constitution  and  forms  creatinine;  on  complete 
hydrolysis,  it  gives  urea  and  sarcosine. 

NH  --  CO 

CREATININE,  NH  :  C(^  ,  is  a  weak  base  and  dissolves  very  readily  in 

\N(CH3)  .  CH2  % 

water,  giving  creatine  again.  It  is  one  of  the  constituents  of  urine  and  forms  a  character- 
istic zinc  salt,  2  mols.  of  creatinine  combining  with  1  mol.  of  ZnCl2.  When  hydrolysed, 
it  gives  ammonia  and  methylhydantoin. 

URIC  ACID   AND   ITS   DERIVATIVES 

When  the  two  amino-groups  of  urea  condense  with  the  two  carboxyl 
groups  of  a  dibasic  acid  with  expulsion  of  2  mols.  of  water,  ureides  (see  above) 

/NH  •  CO 

are    obtained.      Thus,    oxalic    acid    yields    parabanic    acid,    C0\  |     ; 

XNH  •  CO 

NH  *  CO 

malonic  acid,  barbituric  acid,  CO<C^TTT  .  p,O>CH2  ;    tartronic    acid,    dialuric 


acid,  and  mesoxalic  acid,  alloxan,  CO<C^rTT  .  p/O>CO.     If,  however,  only  one 

molecule  of  water  is  eliminated,  one  amino-  and  one  carboxyl-group  remaining 
unchanged,  uro-acids  are  obtained,  e.g.,  oxaluric  acid,  NH2  •  CO  '  NH  •  CO  '  C02H, 
and  alloxanic  acid  (from  mesoxalic  acid). 

These  ureides  are  usually  well  crystallised,  and  are  aminic  and  also 
markedly  acid  in  character.  On  hydrolysis,  they  give  first  the  corresponding 
uro-acid  and  then  urea  and  free  acid.  They  are  sometimes  formed  on  oxida- 
tion of  di  ureides  (see  below)  ;  thus  parabanic  acid  is  obtained  by  oxidising 
uric  acid  with  nitric  acid.  The  alcohol-acids  and  the  aldehydo-acids  also 
give  such  condensations  (see  above),  yielding,  for  example,  hydantoin,  kydantoic 
acid,  and  allanturic  acid  (from  glyoxylic  acid). 

When  2  mols.  of  urea  take  part  in  the  condensation,  diureides  are  obtained, 
these  forming  the  group  containing  uric  acid, 

a)  HN  --  CO  (6) 

I  0) 

(2)  CO      (5)  C—  NH\ 

1  II  >CO  (8) 

(3)  NH  --  C—  NHX 

(4)         (9) 

and  its  derivatives  :  xanthine,  caffeine,  theobromine,  guanine,  hypoxanthin  e, 
alloxanthine,  purpuric  acid,  allantoin,  etc.  The  positions  of  the  substituent 
groups  are  indicated  by  the  bracketed  numbers  shown  in  the  above  formula  for 
uric  acid.  During  recent  years  successful  attempts  have  been  made,  by  means 
of  -ethyl  cyanoacetate,  to  synthesise  all  these  xanthine  bases  and  to  convert 
them,  one  into  the  other  (see  Berichte  der  deutsch.  chem.  Gesells.,  1899,  32, 
p.  435). 

As  a  general  rule,  the  ureides  and  diureides  have  a  more  or  less  marked 
acid  character  and,  as  they  contain  no  carboxyl  group,  this  acidity  is  explained 


436 


ORGANIC     CHEMISTRY 


as  due  to  the  existence  of  these  compounds  in  tautomeric  forms,  just  as  is 
the  case  with  succinimide, 


CH2— 


>NH.     In  the  latter  it  is  assumed  that 


CH2— CO' 


the  iminic  hydrogen  atom  is  very  mobile  and  undergoes  displacement  and 
union  with  the  oxygen  of  the  neighbouring  carbonyl  group,  a  double  linking 
between  carbon  and  nitrogen  being  formed  and  an  acid  hydroxyl  group 
capable  of  forming  salts  with  metals.  The  tautomeric  formula  of  Succinimide 
CH2  •  C(OHk  xN  :  C  •  OH 


would  hence  be 


CH, 


CO 


N,  and  that  of  Parabanic  Acid, 


N  :  C  •  OH 


similar  formulae  hold  for  uric  acid  and  barbituric  acid,  the  latter  functioning 
as  a  dibasic  acid  (in  this  case,  however,  the  acid  character  is  perhaps  to  be 
attributed  to  the  hydrogen  of  the  methylene  group,  CH2). 

Several  diureides  are  found  in  nature,  e.g.,  in  guano,  in  the  urine  and 
muscles  of  carnivora,  in  the  excreta  of  serpents,  in  articular  concretions,  and 
in  certain  plants  (theobromine  in  cocoa,  caffeine,  etc.), 

The  constitutional  formulae  of  the  more  important  diureides  are  as  follow : 


CO 


,N(CH8)— CO 

\  I 

XN(CH3)— CO 


C0( 


,NH-C(CH3)X 


CH 


O 


-CO' 


Dimethylparabanic  acid 
(Cholestrophane) 


Metbyluracil 


< 
/|CO-NH 

I      CO-NH 
<CO-HN> 

Alloxanthine 


—  NH 
-> 


NH—  CH 


CO 


CO 


CH. 


CH, 


Murexide 

N-C-N      • 
II       II  >CH 

CH   C  — NH/ 

I     i 

N=CH 

Purino 

N  — CO 

I     i 

CO    CH  •  NH  •  CO  •  NH2 
•N  — CO 

Dimethylpseudouric  acid 


2   CO— NH' 

Allantoin 


N  — C  — N 


\ 


CC1 


CC1  C  —  NH 


Trichloropurine 


CO  C— NH^ 


CH3-N  — CO 

Theophylline 


JCH 


^±13  •  S 

( 

—                 v 

II                      /CH 
)O    C—  N(CH3)/ 
i 

II 

CH 

V_y  

II 

C- 

>H 
-NH/ 

CO 

1 

c- 

> 

-NH/ 

CH8-1 

I  —  CO 

I 

yH 

-CO 

NH 

—  CO 

Caffeine 

Hypox: 

mthine 

Xanthine 

CH 


N  — C  —    N 

I!      II 

CH    C  — NH 

!      I 

N  =  C  •  NH2 

Adenine 


\CH 


NH— C  —  N 

I  II 

NH:C          C  — NH' 

!        I 

NH  —  CO 

Guanine 


\ 


CH 


COCOA    AND    CHOCOLATE  437 

URIC  ACID,  C5H4O3N4.  Syntheses  of  uric  acid  are  many  and  various ;  from  cyano- 
acetic  acid,  or.glycocoll  or  isodialuric  acid,  by  heating  with  urea;  from  aminobarbituric 
acid  and  potassium  cyanate ;  from  ethyl  acetoacetate  and  urea,  passing  through  methyl  - 
uracil,  nitrouracil,  hydroxyuracil,  and  isodialuric  acid.  The  following  scheme  represents 
the  various  steps  of  the  synthesis  frpm  malonic  acid  :  1 

NH9  CO -OH  NH  — CO  NH  — CO 

I  i  I      1  li 

CO  CH2 >         CO       CH2 >          CO        C:N-OH > 

I  I  II'  II 

NIT  CO -OH  NH  — CO  NH  —  CO 

Urea  Malonic  acid  Barbituric  acid  Violurie  acid 

NH  — OC  NH  — CO  NH  — CO 

I  !  II  II 

CO        CH-NH2       — >          CO        CH  — NHX          — >       CO       C  —  NIL 

II  I        I  >co  i        ||         >co 

NH  — CO  NH  — CO      NH/  NH  — C  — NH/ 

Uramil  Pseudouric  acid  Uric  acid 

Uric  acid  is  a  feeble  dibasic  acid  (see  above),  and  forms  a  white,  amorphous  substance 
insoluble  in  alcohol  or  ether  and  almost  insoluble  in  water.  It  dissolves,  however,  in 
concentrated  sulphuric  acid,  from  which  it  separates  unchanged  on  dilution  with  water. 
It  is  extracted  from  guano,  the  excrements  of  serpents,  and  the  urine  of  carnivora. 

Evaporation  of  uric  acid  with  dilute  nitric  acid  and  treatment  of  the  residue  with 
ammonia  yields  murexide,  which  forms  yellowish  green  crystals  which"  give  a  purple 
aqueous  solution,  turning  blue  on  addition  of  alkali  (characteristic  reaction  for  uric 
acid ). 

THEOBROMINE  (3  :  7-Dimethyl-2  :  6-dioxypurine),  C?H8O2N4  or 

CH3  •  N  —  C—       — N. 

II  >CH 

CO     C  —  N(CH3)/ 

NH— CO 

is  extracted  by  means  of  boiling  alcohol  from  cocoa,2  de-fatted  and  made  into  a  paste  with 

1  The  constitution  of  uric  acid  was  demonstrated  first  by  Medicus,  and  later,  by  various 
syntheses,  by  E.  Fischer  (Liebig's  Annalen,   1882,  215,  p.  253).     The  presence  of  a  chain, 
— C — C — C — ,  and  of  a  carbonic  acid  residue  is  shown  by  the  formation  of  urea  and  alloxan  when 
uric  acid  is  treated  in  the  cold  with  nitric  acid.     The  presence  of  four  imino-groups  is  deduced  from 
the  fact  that,  by  introduction  of  four  methyl  groups  and  subsequent  hydrolysis,  the  four  atoms 
of  nitrogen  are  eliminated  as  methylamine.     A  large  part  of  the  uric  acid  molecule  is  rendered 
evident  jby  the  formation  of  allantoin  (of  known  constitution)  on  oxidation  with  alkaline  perman- 
ganate, and  by  the  formation  of  methylurea  and  methylalloxan  on  oxidation  of  dimethyluric 
acid. 

2  Cocoa  and  Chocolate.     Cocoa  is  placed  on  the  market  in  the  form  of  large  violet  seeds  of 
Theobroma  cacao,  which  grows  well  in  the  Antilles,  Mfexico,  Guatemala,  Java,  Borneo,  Esmeralda 
(equator),  etc.     The  red  or  brown  mature  fruits  resemble  cucumbers,  each  containing  fifty  to 
sixty  seeds  like  beans.     The  seeds  are  separated  from  the  pulp,  heaped  in  casks  for  four  to  five 
days  to  initiate  the  fermentation  which  increases  the  aroma,  and  then  dried  in  the  sun.     The 
chemical  composition  of  the  decorticated  seeds  differs  considerably  with  the  variety  :  fatty 
substance  (cocoa-butter),  40  to  55  per  cent.;   proteins,  10  to  18  per  cent.;   cellulose,  3  to  6  per 
cent. ;  sugars  and  starch,  8  to  15  per  cent. ;   theobromine,  0-8  to  2-5  per  cent. ;   ash,  3  to  4  per 
cent.     Cocoa-butter  (or  cacao-butter)  is  extracted  by  pressing  the  seeds  hot,  and  forms  a  faintly 
yellow  mass  of  pleasing  odour;   it  melts  at  29°  to  31°,  and  contains  the  glycerides  of  arachic, 
palmitic,  oleic,  stearic,  and  lauric  acids. 

In  the  manufacture  of  chocolate,  the  seeds  are  washed  in  suitable  sieves- and  then  gently 
and  cautiously  heated  for  thirty  to  forty  minutes  to  facilitate  skinning.  They  are  next  crushed 
in  mortars  or  rotating  cylinders,  the  flour  obtained  being  made  into  a  paste  with  sugar  and 
worked  for  a  long  time  on  heated  stone  rollers,  different  ingredients  and  flavouring  matters  being 
added  to  give  the  different  kinds  of  chocolate ;  the  homogeneous  paste  then  passes  to  the  moulds. 


438 


ORGANIC     CHEMISTRY 


lime.  Synthetically  it  is  obtained  by  treating  the  lead  salt  of  xanthine  with  methyl 
iodide,  or  from  methyluric  acid  and  phosphorus  oxychloride.  It  forms  white,  anhydrous 
crystals  which  have  a  bitter  taste  and  dissolve  only  slightly  in  water,  alcohol  or  ether. 
It  is  soluble  in  acids  or  alkalies,  and  at  290°  volatilises  without  melting.  It  behaves  as  a 
weak  acid  and  as  a  weak  base.  With  methyl  iodide  the  silver  salt  yields  caffeine.  With 
concentrated  nitric  acid,  chlorine  and  ammonia,  it  gives  the  same  reactions  as  caffeine 
(see  below).  In  the  form  of  different  salts,  theo bromine  is  used  as  a  stimulant  and  diuretic. 
Before  the  war  it  cost  about  72s.  per  kilo. 

CAFFEINE  or  THEINE,  C5H(CH3)3O2N4  +  H2O,  is  trimethylxanthine  or  methyl- 
theobromine  (for  constitution,  see  p.  436).  It  is  an  alkaloid  formed  in  varying  proportions 
(0-5  to  2  per  cent. )  in  coffee  seeds.1  The  leaves  of  the  coffee  plant  C9ntain  up  to  1-3  per  cent., 


Good  chocolate  contains  from  40  to  60  per  cent,  of  cocoa,  the  rest  being  sugar ;  ordinary  qualities 
contain  10  to  15  per  cent,  of  starch. 

The  amounts  of  cocoa  imported  by  various  countries  are  as  follows  (tons ) : 


United 
States 

Germany 

Great 
Britain 

France 

Holland 
(one  half 
re-3xported) 

Belgium 
(one  half 
re-exported) 

Spain 

Switzer- 
land 

Italy 

5J190T     . 

39,239 

34,515 

25,900 

23,180 

22,870 

/  5,963 

5,652 

7,124 

1,456 

1910     . 

52,546 

43,941 

32,046     25,076       34,229 

9,881 

5,517       9,089 

1,886 

1912     . 

69,447 

55,085 

34,145  ;  26,890       41,858 

13,023       5,241      10,342 

2,432 

1913     . 

70,660 

52,878 

35,543     27,610       46,810 

11,620 

6,166      10,248 

2,457 

1914     . 

80,479 

— 

42,416     26,085 

52,375 

•    6,911      10,078 

2,275 

1916     . 

110,050 

— 

90,237 

37,172 

21,112 

— 

7,504 

14,705 

6,746 

1918     . 

— 

— 

— 

— 

— 

—             —     ,      — 

5,863 

The  cocoa  crop  in  the  British  colony  of  the  Gold  Coast  increased  from  5770  tons  in  1904 
to  40,640  tons  in  1911;  in  the  German  colonies,  especially  the  Cameroons,  the  crop  rose  from 
1454  tons  in  1905  to  5500  tons  in  1912. 

Italy  imported  and  exported  the  following  quantities  of  chocolate  : 


Importation 
Exportation 


fTons 


1908 

.     1,090 
£  .       — 

230 


1910 

1,500 
180,000 

230 

30,704 


1913 
2,078 
216,160 


1914 

1,627 


1916 
876 


273  308  362 

38,266         69,544 


1918 

211 
59,120 

336 

107,584 


Before  the  war  the  price  of  cocoa  was  about  £4  per  cwt. 

1  Coffee  consists  of  the  seeds  of  one  of  the  Rubiacese  (Coffea  arabica)  which  grows  naturally 
in  Southern  Ethiopia  and  Arabia,~and  is  cultivated  on  an  enormous  scale  in  India,  the  Antilles, 
Madagascar,  and  South  America.  It  is  an  evergreen  plant,  6  to  9  metres  high  and  of  pyramidal 
habit,  with  greyish  branches  and  lanceolated  leaves,  the  flowers  (at  the  base  of  the  leaf)  being 
white  and  pleasant-smelling,  like  jessamine.  The  fruit  forms  drupes  like  cherries,  the  epicarp 
passing  from  yellow  to  green  to  red  to  brownish,  and  the  mesocarp  being  yellow,  pulpy  and  of 
agreeable  taste.  The  endocarp  is  divided  into  two  compartments  surrounded  by  coriaceous 
membrane  and  each  containing  a  seed,  which  has  one  convex  and  one  flat,  furrowed  face,  and 
is  covered  by  a  friable  pellicle ;  the  endosperm  (albumen )  is  yellowish  or  greenish  and  horny. 

Coffee  berries  are  composed  of  cellulose  (18  per  cent. ),  fatty  matters  (12  per  cent. ),  gummy  and 
saccharine  substances  (10  per  cent.),  nitrogenous  compounds  (12  per  cent.),  mine^jQ  salts 
(4  to  5  per  cent.),  a  tannin  (caffetannic  acid,  8  per  cent.),  caffeine  (0-8  to  1-3  per  cent.),  caffearine, 
and  water  (11  per  cent.).  When  roasted,  coffee  develops  aroma  and  loses  15  to  20  per  cent,  in 
weight,  but  increases  in  volume  by  one-third,  while  the  sugar  caramelises  and  the  cellulose 
carbonises  partially,  forming  a  brown  oil  which  is  denser  than  water,  dissolves  in  ether,  and 
constitutes  the  aromatic  substance  (caffeone).  Roasted  coffee  contains,  on  the  average,  1-5  per 
cent,  of  water,  13  per  cent,  of  nitrogenous  substances,  0-8  per  cent,  of  sugars,  13-5  per  cent,  of  fats, 
4-8  per  cent,  of  ash,  0-9  per  cent,  of  caffeine,  and  46  per  cent,  of  non -nitrogenous  substances ;  to 
hot  water  this  coffee  gives  up  about  25  per  cent,  of  its  weight. 

The  form  of  the  seed  varies  with  the  kind  of  the  coffee  (Coffea  mauritiana,  laurina,  liberica, 
etc. ).  Mocha  coffee  berries  are  small  and  the  Australian  ones  large,  whilst  those  from  the  Antilles 
are  intermediate  in  size. 

The  quality  of  coffee  is  influenced  by  the  methods  of  cultivation  and  preparation  :  by  the 
ordinary  or  dry  method  the  fruit  is  dried  in  the  sun,  so  that  it  may  be  freed  from  the  parchment- 
like  membrane  and  partly  from  the  silvery  pellicle  by  beating  in  a  husking  machine.  In  the  West 
Indies  and  Brazil,  however,  more  use  is  now  made  of  the  wet  process,  in  which  the  fresh  fruit  is 
carried  by  a  stream  of  water  into  a  de-pulping  machine  fitted  with  revolving  channelled  or  toothed 
discs  or  cylinders,  the  seeds  after  this  treatment  being  covered  only  with  the  parchment  integu- 
ment and  with  a  little  pulp,  which  is  eliminated  by  fermentation  and  subsequent  washing ;  finally 


COFFEE    SUBSTITUTES 


439 


larger  proportions  occurring  in  the  leaves  of  the  tea  plant  (1-2  to  4  per  cent.),1  in  cola  nuts 
(2  to  3  per  cent. ),  in  mate  leaves  (or  Paraguay  tea ;  about  1  per  cent. )  and  in  guarana  paste 
(made  from  the  seeds  of  Paullinia  sorbilis,  grown  in  Brazil :  3  to  5  per  cent. ). 


the  seeds  are  dried  in  the  sun  or  in  an  oven,  and  may  then  be  freed  from  the  parchment  by  de- 
corticating machines.  One  hundred  kilos  of  fresh  fruit  gives  about  20  kilos  of  berries  for  sale, 
these  being  rendered  shiny  by  shaking  them  dry  in  sacks  or  in  levigating  apparatus,  in  which 
finely  powdered  colouring  matters  (indigo,  ultramarine,  chromium  salts,  curenin,  graphite,  etc. ) 
are  often  introduced. 

The  cultivation  of  coffee  has  received  a  considerable  impulse  in  Brazil,  where  as  much  as 
800,000  tons  (more  than  three-fourths  of  the  total  production  of  the  world)  is  now  produced. 
Of  the  Antilles  coffees,  the  most  highly  valued  is  that  from  Porto  Rico.  The  principal  commercial 
varieties  of  coffee  are  named  after  the  countries  where  they  are  grown.  The  output  in  different 
countries  is  as  follows  (tons ) : 


Brazil 

Other  American 
countries 

Asia  and"  Oceania 
(except  Arabia) 

Africa  and 
Arabia 

Whole  world 

1900-1901 
1904-1905 
1909-1910       . 
1913-1914 

675,700 
632,000 
1,150,000 
680,000 

170,000 
181,400 
36,000 
85,000 

46,100 
39,500 
26,000 
36,000 

11,300 
8,200 
1,500  (?) 
1,000  (?) 

910,000 
861,000 
1,300,000 
850,000  (?) 

In  1902  the  mean  consumption  per  head  in  kilos  amounted  to  :  Holland,  6-6 ;  Norway,  5-3 ; 
Sweden,  5-2;  United  States,  5-1;  Belgium,  4-7;  Denmark,  3-4;  Germany,  3;  France,  2-2; 
Austria,  0-9;  Italy  0-5;  Spain,  0-5;  Great  Britain,. 0-43. 

The  total  importation  is  as  follows  (tons ) : 


Belgium 

Holland 

Germany 

France 

(one-third 

(two-thirds 

g?',e                Italy            Spain 

re-exported) 

re-exported) 

1 

1907 

189,600 

53,596       101,570 

113,350 

117,857 

426,487        21,476       11,292 

1910 

171,000 

47,600        112,000 

50,000 

120,000 

364,876        25,287    i  12,838 

1912 

171,000 

34,200        111,240 

50,000        116,250 

427,516        27,627       13,378 

1913 

168,000 

43,000        115,280 

53,480 

144,950 

387,000        28,659       15,129 

1914 

— 

52,680        116,420 

124,950 

458,620        28,197       13,733 

1916 

— 

82,880        153,000 

— 

89,000 

529,297        48,961       16,383 

1918 

— 

;             

— 

•  — 

—            51,638    ,      — 

In  1900  Italy  imported  14,100  tons  of  coffee,  in  1908  22,760,  and  in  1910  25,300  tons  (£1,062,080) 
(about  four- fifths  from  Brazil) ;  the  Customs'  duty  was  £60  per  ton  until  1909,  after  which  it  was 
lowered  somewhat.  Pre-war  prices  per  cwt.  at  Genoa,  exclusive  of  duty,  were  :  .Mocha,  £4; 
Porto  Rico,  72s. ;  Peru,  50s. ;  Salvador,  56s. ;  San  Domingo,  44s.  (washed  60s. ) ;  Santos,  42s. ; 
Rio,  38s. ;  Bahia,  36s. 

In  1909,  coffee  became  a  State  monopoly  in  Italy,  the  retail  price  being  raised  in  January,  1920, 
to  14s.  to  17s.  (18  to  22  lire )  per  kilo,  according  to  the  quality;  before  the  war,  the  price  was  3s.  6d. 
to  4s.  Qd.  (including  Is.  2d.  duty ). 

Coffee  Substitutes.  These  are  now  numerous,  and  as  a  rule  contain  no  caffeine,  being 
obtained  by  roasting  roots,  saccharine  fruits,  cereals,  leguminous  seeds,  etc.  On  roasting,  the 
saccharine  substances  form  caramel  and  other  bitter  substances  giving  colour,  taste  and  smell 
to  the  aqueous  decoction.  Chicory  coffee  contains,  on  the  average  :  water,  8  per  cent. ;  nitro- 
genous substances,  7 ;  fats,  2-5;  sugar,  16;  non-nitrogenous  extractives,  52  (9  per  cent,  induline 
and  12  per  cent,  caramel);  cellulose,  10,  and  ash,  5  per  cent.;  about  65  per  cent,  is  soluble  in 
water. 

Beet  coffee,  carrot  coffee,  etc.,  are  also  sold,  and  in  Germany  and  Austria  large  quantities  of 
fig  coffee  are  used,  this  being  often  mixed  with  coffee  made  from  dates,  carobs,  lupins,  wheat,  rye, 
barley,  maize,  malt,  acorns,  chestnuts,  arachis  nuts,  etc. 

These  substitutes  may  be  distinguished  from  coffee  by  microscopic  examination,  by  their  small 
proportion  of  fat  (1  to  3  per  cent.,  whereas  coffee  contains  up  to  14  per  cent.),  and  by  the  high 
content  of  saccharine  substances  (3  to  50  per  cent.,  while  coffee  contains  2  per  cent,  at  most). 

1  Tea  is  an  evergreen  shrub  (Thea  viridis,  Thea  bohea,  and  Thea  assamica),  cultivated  in  China, 
Japan,  British  India,  Java,  Ceylon,  and  Brazil.  The  leaves  are  similar  to  those  of  the  white 
willow,  and  contain  various  enzymes,  of  importance  being  an  oxydase  which,  under  suitable 
conditions  of  temperature  and  moisture,  transforms  the  green  matter  into  a  black  substance 
(the  tannins  being  oxidised ).  The  oxydase  is  more  sensitive  to  heat  than  other  enzymes  producing 
the  aroma,  so  that  if  the  leaves  are  heated- for  more  than  an  hour  at  70°  for  green  tea  or  at  80°  for 
black  tea,  the  maximum  aroma  is  developed,  while  the  tannin  (oxidised)  and  theine  (volatilised) 
are  diminished  in  amount  and  the  soluble  substances  increased  (Sawamura,  1912).  For  black  tea 


440 


ORGANIC     CHEMISTRY 


Industrially  caffeine  may  be  extracted  from  coffee,  tea,  or  mate  leaves,  in  which  it  is 
partly  combined  with  tannic  acid,  by  decomposing  the  compound  with  water  and  then 
treating  with  chloroform,  which  readily  dissolves  it  (from  coffee  it  may  be  extracted  directly 
with  benzene,  which  takes  out  the  oil  also ;  after  evaporation  of  the  benzene,  the  caffeine  is 
separated  by  means  of  water,  the  oil  remaining  insoluble ).  Tea  residues  may  be  extracted 
directly  with  solvents  such  as  alcohol,  previous  pulping  with  lime  (as  used  in  the  case  of 
guarana  paste)  not  being  always  necessary.  During  the  war  a  certain  amount  of  caffeine 
was  obtained  in  Italy  by  extraction  of  the  soot  deposited  in  the  flues  of  the  apparatus  used 
for  roasting' coffee. 

Synthetically  caffeine  may  be  prepared  by  methylating  3-methylxanthine,  1  :  7-dimethyl- 
xanthine  (paraxanthine )  or  3 :  7-dimethylxanthine  (theo bromine)  by  means  of  methyl 
iodide  and  caustic  soda. 

Pure  caffeine  forms  white,  silky,  odourless  needles  of  bitter  taste ;  at  100° 
it  loses  the  molecule  of  water  of  crystallisation,  and  it  sublimes  readily  and  melts 
at  228°  to  230°.  It  dissolves  readily  in  chloroform,  to  some  extent  in  boiling 
water,  slightly  in  alcohol  or  cold  water,  and  very  slightly  in  ether.  It  dissolves 
in  acids  forming  unstable  crystallisable  salts.  When  heated  gently  to  dryness 
with  a  little  chlorine  water  and  concentrated  nitric  acid,  it  leaves  a  reddish- 
yellow  residue  which  gives  a  purple- violet  coloration  with  a  little  ammonia. 
Before  the  war  it  cost  £2  per  kilo,  but  during  the  war  it  was  sold  in  Italy  at  £  12 
(300  lire)  per  kilo. 

GUANINE,  C5H5ON-  (constitution  given  above),  is  a  di-acid  base,  but  forms  salts 
also  with  bases.  It  is  a  white  powder  insoluble  in  water  but  soluble  in  ammonia.  On 
oxidation  with  potassium  chlorate  and  hydrochloric  acid,  it  gives  carbon  dioxide,  para- 
banic  acid,  and  guanidine. 


the  leaves  ar§  allowed  to  wither  and  soften  in  the  sun,  and  are  then  rolled  up  and  covered  with 
moist  cloths  to  accelerate  the  fermentation,  which  transforms  the  green  into  black  substances. 
Rolling  of  the  leaves  results  in  rupture  of  the  cells  and  expression  of  the  juice  which  facilitates  the 
fermentation ;  when  the  latter  ceases  (in  a  few  hours)  the  material  is  spread  either  on  iron  plates 
heated  over  direct  fire  or  on  gratings  heated  with  hot  air  (not  over  80° ).  To  prepare  green  tea, 
the  withered  leaves  are  subjected  to  rapid  treatment  with  boiling  water  or  steam  to  destroy  the 
oxydase  (the  enzymes  producing  the  aroma  are  more  resistant),  so  that  the  green  colour  may  be 
preserved.  The  prepared  tea  is  kept  in  sealed  boxes  of  metal  foil,  in  order  that  extraneous  odours 
may  not  be  absorbed. 

From  4  kilos  of  leaves  1  kilo  of  dry  tea  is  obtained.  Commercially  the  numerous  varieties 
are  grouped  into  three  types  :  green,  black,  and  scented,  the  last  two  being  slightly  fermented. 
The  active  alkaloid  is  Theine  (see  above).  The  best  infusion  of  tea  is  obtained  by  macerating 
for  thirty  minutes  in  cold  water  and  then  adding  boiling  water,  the  liquid  being  poured  off  before 
it  becomes  very  brown  and  excessively  rich  in  tannin  (20  grams  of  tea  per  litre  of  slightly  hard 
water). 

The  world's  output  of  tea  is  about  600,000  tons,  and  is  furnished  almost  entirely  by  Asia  [55 
per  cent,  from  China  and  the  rest  from  India  (120,000  tons),  Ceylon  (85,000  tons),  Japan  (28,000 
tons),  Formosa,  and  Java]. 

The  consumption  of  tea  in  different  countries  is  shown  by  the  following  amounts  imported 
(tons ) : 


Great  Britain 

Belgium 

(one-sixth 

Eussia 

Trance          Holland 

(two-thirds 

Spain 

Italy 

re-exported) 

fc 

re-exported) 

1907        143,846 

92,856 

44,959 

1,155          4,174 

766 

143 

74 

1910        150,522 

70,172 

44,501 

1,261          4,970 

749 

156 

74 

1912 

163,771 

68,509 

44,772 

1,309          5,508 

1,051 

187 

87 

1913 

165,580 

78,513 

40,378 

1,207          5,467 

586 

214 

95 

1914        168,705 

78,271 

44,466 

1,980          6,461 

— 

122 

75 

1916 

171,306 

78,400 

47,522 

2,645          8,185 

— 

202 

106 

Other  imports  were  in  1913  (tons):  Canada,  16,300;  Austria,  2,000;  Denmark,  467; 
Roumania,  350;  Switzerland,  528;  Argentine,  1880;  Chili,  1746;  Persia,  4770,  and  Australia, 
16,940. 

Before  the  war,  tea  was  sold  in  Italy  at  3s.  to  6s.  per  kilo  (including  the  import  duty  of  2s. ), 
according  to  the  quality. 


XAN THINE,   ADENINE  441 

XANTHINE,  C5H4O2N4  (constitution  given  above),  is  a  white  powder  and  acts  as 
both  acid  and  base.  It  is  obtained  from  guanine  by  the  action  of  nitrous  acid,  and  its 
lead  salt  reacts  with  methyl  iodide,  giving  theo bromine. 

ADENINE,  C5H5N5  (constitution  given  above),  forms  shining  needles  and  is  a  base 
occurring  in  tea  and  in  ox-pancreas.  It  is  formed  by  decomposition  of  the  nuclein  of 
the  cell-nuclei  and  is  hence  of  physiological  importance. 


INDEX 


ABRIN,  138 

Abrus  prrecatorius,  138 

Acetaldehyde,  250 

Estimation,  251 
Acetals,  245 
Acetamide,  238,  421 
Acetamidine,  426 
Acetamido-chloride,  425 
Acetates,  345-348 
Acetic  anhydride,  380 
Acetifiers,  342 
Acetimino-chloride,  425 
Acetiminothiomethyl  hydriodide,  425 
Acetins,  257,  274 
Acetoacetaldehyde,  399 
Acetobromamide,  420 
Acetometers,  344 
Acetonamines,  252 
Acetone,  129,  254 
Acetonealcohol,  397 
Acetone-chloroform,  119 
Acetonitrile,  238 
Acetonylacetone,  399 
Acetoxime,  252 
Acetyl  chloride,  379 

iodide,  380 

number,  224 

sulphide,  419 
Acetylacetone,  398 
Acetylcarbinol,  397 
Acetylcellulose,  381 
Acetylene,  111 

hydrocarbons,  110 
Acetylethylamine,  420 
Acetylglycocoll,  424 
Acetylhydrazides,  426 
Acetylides,  110,  361 
Acetylurea,  433 
Achroodextrin,  141 
Acichlorides,  379 
Acid,  Abietic,  206 

Acetaldehydedisulphonic,  257 

Acetic,  328 

Acetoacetic,  396 

Acetonediacetic,  411 

Acetonedicarboxylic,  411 

Acetonetricarboxylic,  419 

Acetonic,  389 

Aceturic,  385,  424 

Acetylenecarboxylic,  361 

Acetylenedicarboxylic,  376 

Aconitic,  376,  411 

Acrylic,  354 

Adipic,  357,  362 

Alkylphosphonic,  242 

Allanturic,  435 

Allocroto'nic,  355 

Allophanic,  433 

Alloxanic,  435 

•y-Allylbutyric,  357 


442 


Acid,  Allylsuccinic,  373 

Aminoacetic,  379,  385,  423 

Aminoethylsulphonic,  257 

a-Aminoglutaric,  424 

a-Amino-j8-hydroxypropionic,  424 

a-Aminoisocaproic,  424 

o-Aminopropionic,  423 

Aminosuccinic,  424 

a-Amino-j8-thiolactic,  396 

Amylacetylenecarboxylic,  360 

Amylmalonic,  369 

Angelic,  356 

Arabonic,  392 

Arachidic,  320 

Aspartic,  424 

Azelaic,  365,  372 

Azulmic,  427 

Barbituric,  435,  437 

Behenic,  320 

Behenolic,  360,  362 

Brassidic,  360 

Brassylic,  360,  365 

Bromosuccinic,  374 

Butylacetylenecarboxylic,  360 

Butylfumaric,  373 

Butylmaleic,  373 

Butylmalonic,  369 

Butylsuccinic,  371 

Butyric,  348 

Cacodylic,  242 

Caffetannic,  438 

Camphoronic,  376 

Capric,  350 

Caproic,  349 

Caprylic,  349 

Carbamic,  431 

Carbaminic,  431 

Cerotic,  351 

Cetylmalonic,  369 

Chloroacetic,  379 

a-(B-,  7-)  Chlorobutyric,  378 

Chlorocarbonic,  431 

o-(0-)  Chloropropionic,  378 

Citraconic,  22,  375 

Citramalic,  400 

Citric,  412 

Citronellic,  357 

Citrylideneacetic,  364 

Crotonic,  22,  354 

Cyanic,  427 

Cyanoacetic,  377 

Cyanuric,  428,  431 

Cyclogeranic,  363 

Decamethylenedicarboxylic,  365 

Decoic,  350 

Dehydroundecenoic,  361 

Desoxalic,  419 

Diacetosuccinic,  411 

Diacetylenedicarboxylic,  376 

Diacetylglutaric,  411 


INDEX 


443 


Acid,  Dialkylphosphonic,  242 
Diallylacetic,  363 
Dialuric,  435 
oS-Diaminovaleric,  392 
Diaterebinic,  400 
j87-Dibromobutyric,  355 
£j8-Dibromopropionic,  378 
Dicetylmalonic,  369 
Dichloracetic,  378 
aa-(aB-)  Dichloropropionic,  378 
Diethylmaleic,  373 
Diethylmalonic,  369 
Diglycollic,  384 
o8-Dihydroxybutyric,  355 
Dihydroxymalonic,  410 
ajS-Dihydroxypropionic,  392 
Dihydroxystearic,  359,  390,  392 
Dihydroxytartaric,  411 
Diisoamylmalonic,  369 
Diisobutylmalonic,  369 
Dimethylacetic,  349 
o0-Dimethylacrylic,  356 
Dimethylarsenic,  242 
Dimethylfumaric,  375 
aa-(cr/-,  77-)  Dimethylitaconic,  373 
Dimethylmaleic,  375 
Dimethylmalonic,  369 
Dimethyloxaminic,  240 
Dimethylparabanic,  436 
Dimethylpseudouric,  436 
Dimethylsuccinic,  371 
Dioctylmalonic,  369 
Dipropylmalonic,  369 
Dithiocarbamic,  434 
Dithiocarbonic,  433 
Dithiocarbonylic,  433 
Dodecamethylenedicarboxylic,  365 
Elaeostearic,  364 
Elaidic,  359 
Erucic,  360 
Erythric,  392 
Ethanetricarboxylic,  411 
Ethanthiolic,  419 
Ethan thioltbiolic,  419 
Ethylacetylenecarboxylic,  360 
Ethylcarbonic,  431 
Ethyleneaminosulphonic,  424 
Ethyleaelactic,  389 
Ethylenesuccinic,  370 
Ethylfumaric,  373 
Ethylhydroxamic,  427 
Efchylideneacetic,  355 
Ethylidenelactic,  386 
Ethylidenepropionic,  356 
Ethylidenesuccinic,  371 
Ethylisopropylmalonic,  369 
a-(7-)  Ethylitaconic,  373 
Ethylmaleic,  373 
Ethylmalonic,  369 
Ethylmethylacetic,  349 
Ethylnitric,  236 
Ethylsulphonic,  235 
Ethylsulphuric,  108,  235 
Ethylsulphurous,  235 
Flaveanhydric,  427 
Formic,  324 

Formothiohydroxamic,  429 
Formylacetic,  393 
Fulminic,  428 
Fulminuric,  429 
Fumaric,  22,  374 
Galactonic,  392 
Geranic,  358,  363 
Glucoheptonic,  393 


Acid,  Gluconic,  392 
Glutaconic,  375 
Glutamic,  424 
Glutaric,  366,  372 
Glyceric,  220,  392 
Glycerophosphoric,  258 
Glycolglycollic,  384 
Glycollic,  379,  384 
Glycolsulphuric,  256 
Glycoluric,  433 
Glycuronic,  393 
Glyoxylic,  393 
Gulonic,  392 
Heptoic,  349 

Heptylacetylenecarboxylic,  360 
Heptylsuccinic,  371 
Hexahydrostearic,  364 
Hexantetroloic,  392 
Hexylacetylenecarboxylic,  360 
Hexylsuccinic,  371 
Hippuric,  423 
Hydantoic,  433,  435 
Hydracrylic,  389 
Hydrazoic,  426,  434 
Hydrochelidonic,  411 
Hydrocyanic,  427 
Hydromucic,  373 
Hydromuconic,  375 
Hydroxyacetic,  379,  384 
3-Hydroxyacrylic,  390,  393 
o-(fl-)Hydroxybutyric,  389 
a-Hydroxycaproic,  389 
Hydroxycitric,  419 
Hydroxyethylsulphonic,  257 
o-(^)-Hydroxyglutaric,  400 
a-Hydroxyisobutyric,  389 
a-Hydroxyisovaleric,  389 
Hydroxymalonic,  399 
Hydroxymethylsulphonic,  257 
o-Hydroxymyristic,  389 
Hydroxyoleic,  390 
a-Hydroxypalmitic,  389 
j8-Hydroxypelargonic,  390 
a-Hydroxypropionic,  386 
i3-Hydroxypropionic,  389 
o-Hydroxystearic,  389 
Hydroxysuccinic,  399 
a-Hydroxyvaleric,  389 
Hypogaeic,  358 
Ichthyolsulphonic,  103 
Idonic,  392 

Iminodithiocarbamic,  433 
Iminodithiocarbonic,  433 
Iminothiocarbamic,  433 
^-lodopropionic,  378 
Isethionic,  257 
Isoamylmalonic,  369 
Isobutylaticonic,  375 
Isobutylfumaric,  373 
Isobutylmaleic,  373 
Isobutylmalonic,  369 
Isobutyric,  349 
Isocrotonic,  22,  355 
Isocyanic,  427 
Isoerucic,  360 
a-(/8)  Isofulminuric,  429 
Isolinolenic,  364 
Iso-oleic,  359 

Isopropylacetylenecarboxylic,  360 
Isopropylfumaric,  373 
7-Isopropylitaconic,  373 
Isopropylmaleic,  373 
Isopropylmalonic,  369 
Isosaccharinic,  392 


INDEX 


Acid,  Isosuccinic,  371 
Isovaleric,  349 
Itaconic,  374 
Itamalic,  400 
Jecorinic,  364 
0-Ketobutyric,  396 
Lactic,  383,  386 
Laurie,  320,  350,  362 
Leucinic,  389 
Levulinic,  390,  397 
Lignoceric,  320 
Linolenic,  364 
Linolic,  363 
Lyxonic,  392 
Malamic,  421 
Maleic,  22,  374 
Malic,  399,  421 
.     Malonic,  368,  437 
d-Mannonic,  392 
Margaric,  350 
Melissic,  351 
Mesaconic,  22,  374 
Mesotartaric,  401 
Mesoxalic,  399,  410 
Metacrylic,  356 
Metasaccharinic,  392 
Methionic,  228,  257 
Methylacetylenecarboxylic,  360 
a-Methylacrylic,  356 
3-Methylacrylic,  355 
£-Methy]adipic,  372 
Methylbutylmalonic,  369 
l-Methylcyclohexylidene-4-acetic,  20 
Methylenedisulphonic,  257 
7-Methylene-7-methylpyrotartaric,  373 
Methylenesuccinic,  374 
Methylethylglycollic,  389 
Methylethylitaconic,  373 
Methylethylmaleic,  373 
Methylethylmalonic,  369 
Methylfumaric,  374 
Methylisobutylmalonic,  369 
Methylisopropylmaleic,  373 
Methylisopropylmalonic,  369 
a-(y-)  Methylitaconic,  373 
Methylmaleic,  374 
Methylmalonic,  369 
Methylmethyleneacetic,  356 
Methylpropiolic,  361 
Methylpropylmaleic,  373 
Methylpropylmalonic,  369 
Monochloroacetic,  379,  383 
Monothiocarbamic,  433 
Monothiocarbonic,  433 
Monothiocarbonylamic,  433 
Monothiocarbonylic,  433 
Mucic,  410 
Muconic,  376 
Myristic,  350 
Nitrohydroxylaminic,  246 
Nonoic,  349,  360 
Nonylacetylenecarboxylic,  360 
(Enanthic,  934 
Oleic,  358 
Aa/3-Oleic,  359 
Oxalacetic,  410 
Oxalic,  366 
Oxaluric,  435 
Oxaniic,  421 
Palmitic,  350 
Parabanic,  435,  436 
Paralactic,  389 
Paratartaric,  401 
Pelargonic,  349 


Acid,  Pentadecoic,  320 

Pentylmalonic,  369 

Perthiocyanic,  429 

Picric,  303 

Pimelic,  365 

Pivalic,  349 

as.  Propanetricarboxylic,  411 

s.  Propanetricarboxylic,  376,  411 

Propargylic,  361 

Propinoic,  361 

Propiolic,  361 

Propionic,  348 

Propylacetylenecarboxylic,  360 

Propylfumaric,  373 

Propylitaconic,  373 

Propylmaleic,  373 

Propylmalonic,  369 

Propylsuccinic,  371 

Pseudouric,  437 

Purpuric,  435 

Pyrocinchonic,  375 

Pyroligneous,  335 

Pyrotartaric,  372 

Pyroterebic,  357 

Pyruvic,  383,  396 

Racemic,  21,  400 

Rhamnohexonic,  393 

Rhodanic,  429 

Rhodinic,  358 

Ribonic,  392 

Ricinelaidinic,  390 

Ricinoleic,  390 

Ricinoleinsulphonic,  390 

Roccellic,  365 

Rubeanhydric,  427 

Saccharic,  410 

Saccharinic,  392 

Salicylic,  212 

Sarcolactic,  389 

Sativic,  364 

Sebacic,  358,  365,  372 

Sorbic,  363 

Stearic,  350 

Stearolic,  358,  362 

Suberic,  365,  372 

Succinatmc,  421 

Succinic,  370 

Talonic,  392 

Tariric,  362 

Tartaric,  21,  400 
Artificial,  410 
Manufacture  of,  407 

Tartronic,  220,  399 

Taurocholic,  257,  424 

Telfairic,  364 

Teraconic,  373 

Teracrylic,  357 

Terebic,  357 

Terebinic,  400 

Terpenylic,  357 

Tetrabromostearic,  364 

Tetracetylenedicarboxylic,  376 

Tetrahydroxystearic,  364 

Tetrolic,  356,  361 

Thioacetic,  419 

Thiocyanic,  429 

Thiocyanuric,  429 

Tiglic,  357 

Tricarballylic,  363,  376,  411 

Trichloroacetic,  378 

Trihydroxyglutaric,  410 

Trimesic,  393 

Trimethylacetic,  349 

aa£-Trimethyltricarballylic,  376 


INDEX 


445 


Acid,  Trithiocarbonic,  433 

Undecenoic,  358 

Undecoic,  350 

Undecolic,  361 

Uric,  435 

Valeric,  349 

Vinylacetic,  354 

0-Vinylacrylic,  363 

Violuric,  437 

Xanthic,  434 

Xanthonic,  434 

Xylonic,  392 
Acidol,  424 
Acids,  Affinity  constants,  321 

Heats  of  neutralisation  of  organic,  26 

Alkylsulphonic,  233 

Alkylsulphuric,  235 

Amino,  422 

Dibasic,  234 

Dihydroxystearic,  389 

Diolefinedicarboxylic,  376 

Halogenated,  377 

Heptonic,  393 

Hexabromostearic,  364 

Hexahydroxystearic,  364 

Hexonic,  392 

Homoaspartic,  425 

Hydroxamic,  246,  427 

Hydroximic,  427 

Hydroxy,  383 

Hydroxyolefinecarboxylic,  389 

a-Ketonic,  395 

£-Ketonic,  395 

7-Ketonic,  396 

Ketonic  dibasic,  410 

Lactic,  20,  385 

Monobasic,  234 

Monobasic  aldehydic,  393 

Monobasic  ketonic,  394 

Olefinecarboxylic,  351 

Olefinedicarboxylic,  373 

Polybasic  fatty,  364 

Pyrotartaric,  372 

Saturated  dibasic,  364 

Saturated  monobasic  fatty,  319 

Succinic,  370 

Tartaric,  21,  400 

Tetrabasic,  376 

Tribasic,  234,  376 

Unsaturated  dibasic,  373 

Unsaturated  monobasic  fatty,  351 

Unsaturated     monobasic,   of     the    series 
CnH2n_4Oa»360 

with  two  double  bonds,  362 

with  three  double  bonds,  364    " 

with  triple  linking,  360 
Aconitum  napellus,  376,  411 
Acraldehyde,  251 
Acrolein,  251 
Acrolelnammonia,  252 
Acrose,  393' 
Adenine,  436,  441 
Affinity  constants,  32 1 
Agglutinins,  139 
Agro  cotto,  414,  415 
Alanine,  389,  423 
Albumin,  Living,  137 
Alcohol,  Absolute,  130,  172 
Acetoisopropyl,  398 
Acetone,  397 
Allyl,  216,  327 
Amyl,  126,  165,  215 
Butyl,  125,  126,  214 
Caproyl,  215 


Alcohol,  Capryl,  215 

Ceryl,  126,  215 

Cetyl,  215 

Decyl,  126 

Denatured,  176 

Dodecyl,  126 

Ethyl,  130 

Glycide,  258 

Heptyl,  126,  215 

Hexadecyl,  126,  215 

Hexyl,  215 

Isobutyl,  126,  215 

Isohexyl,  215 

Isopropyl,  126,  214 

Melissyl,  216 

Methyl,  127-130,  173 

Myricyl,  126,  216 

Nonyl,  126 

Octodecyl,  126 

Octyl,  126,  215 

(Enanthyl,  215 

of  crystallisation,  126 

Pentadecyl,  126 

Propargyl,  216 

Propyl,  126,  214 

Tetradecyl,  126 

Tridecyl,  126 

Undecyl,  126 

Vinyl,  216 
Alcohol,  Amylo  process,  155 

Denaturation,  176 

Effront  process,  167 

Fiscal  regulations,  179 

from  beet,  168 

from  calcium  carbide,  171 

from  fruit,  167 

from  lees,  169 

from  molasses,  166 

from  sulphite  liquors,  169 

from  vinasse,  169 

from  wine,  169 

from  wood,  167 

Industrial  preparation  of,  140 

meters,  173 

motors,  178 

Rectification  of,  164 

Solid,  131 

Statistics,  179 

Synthetic,  171 

Tests,  172,  174 

Windisch's  Table,  175 

Yield,  153 
Alcohols,  123 

Aldehydic,  393 

Constitution  of,  124 

Derivatives  of  monohydric,  226 
of  polyhydric,  256 

Dihydric,  216 

Higher  monohydric,  214 

Ketonic,  394,  397 

Nomenclature,  125 
Polyhydric,  217,  224 
Primary,  124,  125  . 

Saturated  monohydric,  124,  126 
Secondary,  124,  125 
Tertiary,  124.  125 
Tetrahydric,  224 
Trihydric,  217 
Unsaturated,  216 
Alcoholene,  178 
Alcoholism,  130,  184 
Alcoholometer,  Gay-Lussac,  174 

Tralles,  174 
Alcoholometry,  174 


446 


INDEX 


Aldehyde-ammonias,  245 
Aldehydes,  116,  124,  243,  244 

Determination  by  Strache's  method,  255 

Schiff's  reagent- for,  246 

with  unsaturated  radicals,  251 
Aldehydo-catalase,  134 
Aldoketenes,  256 
Aldol,  393 
Aldols,  245 
Aldoximes,  246 
Alembics,  158 
Algae,  68 

Aliphatic  compounds,  29 
Alipine,  119 
Alkoxides,  124 
Alkyl  halides,  114 

Estimation  of,  120 
Alkylenes,  106 
Alkylhydrazines,  241 
Alkylhydroxylamines,  24 1 
Alkylisoureas,  432 
Alkyls,  30 
Allantoin,  436 
Allene,  109,  374 
Alloisomerism,  21,  22 
Alloxan,  435 
Alloxanthine,  436 
AHyl  bromide,  123 

chloride,  123 

iodide,  123 

isothiocyanate,  430 

mustard  oil,  430 

thiocyanate,  430 
Allylene,  110,  375 
Amber,  370 
Amidases,  183 
Amides,  253,  419 

of  carbonic  acid,  431 

of  hydro xy-acids,  421 
Amidines,  238,  425,  426 
Amido-chlorides,  425 
Amidoximes,  427 
Amimides,  42£ 
Amines,  239 
Amino-acids,  419 

Derivatives  of,  422 
Aminoguanidine,  434 
Ammelide,  431 
Ammeline,  431 
Ammonal,  311 
Ammoncarbonite,  307 
Ammonium  carbamate,  431 

cyanate,  428 

ichthyolsulphonate,  103 

thiocyanate,  429 
Amygdalin,  136 
Amylacetylene,  399 
Amylase,  133,  134 
Amylene,  109 

hydrate,  215 
Amylo  process,  155 
Amylodextrin,  141 
Amylomyces  Rouxii,  155,  156 
Anaesthesia,  114,  118 
Anaesthetics,  118 
Analysis,  Elementary,  8 

Qualitative,  7 

Quantitative,  8 
Anhydrides,  380 

Internal,  380 

Mixed,  380 
Antialdoximes,  253 
Anti-bodies,  138 
Antiketoximes,  253 


Antilactase,  138 

Antimorphine,  138 

Antipepsin,  138 

Antirennet,  138 

Antiricin,  138 

Antiseptics,  151 

Antitoxins,  138 

Arabitol,  225 

Arginine,  392 

Aromatic  compounds,  29 

Arrack,  190 

Arsines,  242 

j^rtificial  parthenogenesis,  138 

Ascomycetes,  133 

Asparagine,  20,  424 

Aspartamide,  425 

Aspergillus  oryzae,  155 

Asphalte,  99 

Artificial,  99 

mastic,  99 
Asphaltite,  100 
Astatki,  77,  86 

Asymmetric  syntheses,  137  , 

Asymmetry,  Absolute,  22 

Relative,  22 
Atole,  190 
Atractylin,  248 
Attenuation  of  fermented  liquids.  153,  154, 

207 

Axite,  302 
Azides,  426 
Azodicarbonamide,  434 

Bacillus  aceticus,  145,  340 

acidi  laevolactici,  389 

acidificans  longissimus,  152 

butylicus,  214 

Delbrucki,  149 

ethaceticus,  392 

saprogenes  vini,  404 
Bacteria,  Acetic,  145,  340 

Butyric,  145 

Chromogenic,  133 

Lactic,  145 

Pathogenic,  133 

Reproduction  of,  132 

Saprophytic,  133 

Zymogenic,  133 
Bacteriology,  132 
Baekelite,  370 
Balling's  Table,  200 
Ballistite,  300 
Barley,  192 

Malting  of,  195 
Bases,  Aminic,  239 

Ammonium,  239 

Arsonium,  242 

Iminic,  239 

Nitrilic,  239 

Primary,  239 

Quaternary,  239 

Secondary,  239 

Tertiary,  239 

Beckmann  rearrangement,  253 
Beer,  191 

Alcohol-free,  211 

Analysis,  211 

Attenuation,  207 

Cask  pitching,  209 

Composition,  211 

Detection  of  antiseptics  in,  212 

Fermentation,  204 

Mashing,  201 

Pasteurisation,  210 


INDEX 


447 


Beer,  Racking,  209 

Statistics,  212 
Benzene  from  naphtha,  87 
Benzine,  Crude,  84 
Benzoyl,  15 
Bergamot,  413 
Betaine,  385,  423 

hydro-chloride,  423 
Bilineurine,  257 
Biogen  theory,  137 
Bismuth  tribromophenoxide,  122 
Bisulphite  aldehyde  compounds,  244 
Bitumen,  99 
Biuret,  133 
Blastomycetes,  133 
Blood,  137 
Boghead  coal,  100 
Boiling  point,  2,  25 
Boudineuse,  284,  300 
Brandy,  190 
Bromoacetylene,  123 
Butandiene,  113 
Butandiine,  114 
Butandione,  398 
Butanes,  37 
Butanolone,  398 
Butanols,  214 
Butanone,  256 
Butantetrol,  225 
Butenes,  109 
Butyl  iodides,  117,  118 
Butylenes,  109 
Butyramide,  421 
Butyrolactone,  384 
Butyryl  chlorides,  380 


Cacao  butter,  437 
Cacodyl,  15,  242 

chloride,  242 

oxide,  242 
Cadaverine,  257 
Caffeine,  438 
Calcium  acetate,  337 

butyrate,  348 

carbide,  11 

citrate,  415,  417 

cyanamide,  430 

dilactate,  388 

ethoxide.  214 

formate,  328 

lactate,  388 

oxalate,  368 

tartrate,  40 1 

Calorimeter,  Junker's  gas,  61 
Cannel  coal,  100 

powder,  305 
Capillarimeter,  176 
Caprylene,  109 
Caps,  309 
Carbamide,  432 
Carbamidyl  chloride,  432 
Carbazide,  433 
Carbenes,  99 
Carbinol,  125,  127 
Carbocyclic  compounds,  29 
Carbod'iimide,  18,  430 
Carbodiphenylimide,  430 
Carbodynamitc,  284 
Carbohydrazide,  433 
Carbon,  Asymmetric,  19 

chains,  16 

Estimation  of,  8 

oxychloride,  see  Phosgene. 


Carbon  sulphochloride,  433 

tetrachloride,  122 

Valency  of,  15 
Carbonic  acid  esters,  431 
Carbonite,  284,  307 
Carbonites,  306 
Carboxyl,  124 
Carbyl  sulphate,  257 
Carbylamines,  238 
Cart-grease,  98 
Castor  oil,  390 
Catalases,  135 
Catalysts,  Inorganic,  136 

Organic,  136 
Cellase,  134 
Cerasin,  69,  105 
Cereals,  Starch-content  of,  141 
Cerotene,  109 
Cerotin,  215 
Ceryl  cerotate,  216 
Chamberland  flasks,  147 
Champy  drums,  272 
Charcoal,  Wood,  268 
Chartreuse,  190 
Cheddite,  305 
Chica,  190 

Chlamydomucor  oryzse,  155 
Chloral,  251 

hydrate,  251 
Chloralamid<%  421 
Chloramides,  238 
Chloranhydrides,  379 
Chloretone,  119 
Chlorhydrins,  107,  217,  257 
Chlorimides,  238 
Chlorocruorin,  137 
Chloroe  thane,  117 
Chloroform,  118 

Pictet,  119 

Tests  for,  120 
Chloromethane,  116* 
Chlorophyll,  133 
Chloropicrin,  236 
o-Chloropropylene,  123 
Chocolate,  437 
Cholestrophane,  436 
Choline,  257 

Chronograph,  Le  Boulenge's,  317 
Cider,  190 
Citral,  216,  252,  416 
Citrates,  418 
C'itromyces  citricus,  412 

Pfefferianus  and  Glaber,  412 
Citronellal,  252,  358 
Citronellol,  216 
Citrus  bergamia,  413 

industry,  413 

limetta,  413 

limonium,  413 

Classification  of  organic  substances,  29 
Coagulation,  Enzymic,  134 
Coal,  Cannel,  100 

-dust  in  mines,  34 

for  gas,  39 

gas,  38 

tar,  99 
Cocaine,  119 
Cocci,  133 
Cocoa,  437 
Coffee,  438 

substitutes,  439 
Cognac,  190,  191 
Collodion  cotton,  285,  294 
Combustion  furnace,  8 


448 


INDEX 


Condensation,  Aldehyde,  245 

Aldol,  245 

Condenser,  Liebig's,  2 
Conductivity,  Electrical,  29 
Conidia,  133 
Coniine,  20,  110 
Conylene,  110 
Coolers,  Wort,  204 
Cordite,  287,  302 
Cracking  of  oils,  87 
Cream  of  tartar,  401,  402 
Creatine,  435 
Creatinine,  435 
Cremonite,  305 
Creosote  oil,  99 
Crotonaldehyde,  252 
Crotonylene,  110 
Crushers,  262,  315 
Crystalline  form,  24 
Crystallisation,  2 
Crystals,  Hemihedral,  19 

Liquid,  139 

Mixed,  23 
Curacao,  191 
Cyamelide,  427 
Cyanamide,  18,  430 
Cyanates,  427 
Cyanide  black,  104 
Cyanides,  Alkyl,  237 
Cyano-acids,  377 
Cyanogen,  427 

chloride,  427 

compounds,  427 
of  coal-gas,  50 

sulphide,  429 

trichloride,  427 
Cyanohydrins,  238 
Cyanurtriamide,  431 
Cyclic  compounds,  106 
Cycloheptanone,  357 
Cyclohexane,  71 
Cyclo-olefines,  29 
Cycloparaffins,  29 
Cyclopentane,  71 
Cyclopropane,  106 
Cymene,  252 
Cymogen,  37 
Cynarase,  139 
Cysteine,  396,  424 
Cystine,  396,  424 
Cytase,  134 


Decane,  32 

Degree  of  dissociation,  322 

fermentation,  153 

viscosity,  90 
Degrees  Brix,  153 
Dehusker,  145 
Denaturants,  177 
Denatured  alcohol,  176 
Densimeter,  Legal,  207 
Dephlegmators,  77,  158,  162 
Derricks,  66,  74 
Desichthyol,  103 
Desmobacteria,  133 
Desmotropy,  18 
Detonation,  258 
Detonators,  309 
Dextrase,  147 
Dextrinase,  134,  204 
Diacetamide,  421 
Diacethydrazide,  426 
Diacetyl,  398 


Diacetylene,  114 
Diacetylglycol,  217 
Dialdehydes,  393 
Diallyl,  110 
Diamalt,  140 
Diamino-acids,  424 
Diastase,  133,  134,  141 
Diastofor,  140 
Diazo-compounds,  241 
Diazoguanidine,  434 
Diazomethane,  242 
Dibutyramide,  421 
Dicetyl,  32 
Dichlorethane,  118 
Dichlorhydrin,  257 
Dichlormethane,  118 
Dicyanodiamide,  431 
Dieline,  122 
Diethylamine,  241 
Diethylcarbinol,  126,  243 
Diethylcyanamide,  431 
Diethylenediamine,  257 
Diethylsulphone,  233 
Diethylthiourea,  434 
Diglycerol,  218 
Diglycollamides,  421 
Diglycollimide,  421 
Dihydrazides,  426 
Dihydroxyacetonase,  147 
Dihydroxyacetone,  147,  398 
Dihydroxydiethylamine,  257 
Di-isobutyramide,  421 
Diketobutane,  398 
Diketohexane,  399 
Diketonamines,  252 
Diketones,  398 
Dimethylacetamide,  420 
Dimethylacetol,  398 
Dimethylamine,  241 
Dimethylarsenic  acid,  242 

chloride,  242 
Dimethylarsine,  242 
Dimethylcarbinol,  214 
Dimethylethylcarbinol,  126,  215 
Dimethylglyoximej  398 
Dimethylmethane,  36 
Dimethyloxamide,  240 
Dimorphism,  24 
Dinitroacetylglycerine,  274 
Dinitroethane,  237 
Dinitroformylglycerine,  274 
Dinitroglycerine,  273 
Dinitromethane,  237 
Dinitromonochlorhydrin,  274 
Diolefines,  109 
Diplococci,  133 
Dipropargyl,  114 
Dipropionamide,  421 
Distillation,  Fractional,  2,  75 

of  fermented  liquids,  158 

Theory,  3 

Vacuum,  4 

Wood,  330 

Distillery  residues,  Utilisation,  182 
Disulphides,  233 
Disulphoxides,  233 
Dithioglycol  chloride,  257 
Dithiourethane,  434 
Diureides,  435 
Docosane,  32 
Dodecane,  32 
Donnar,  305 
Dormiol,  119 
Dotriacontane,  32 


449 


Dropping-point  of  fats,  0 

Drying  ovens  for  explosives,  271,  294 

Dulcitol,  226 

Durra,  141,  182 

Dynamites,  273,  282 

Analysis,  313 

Gelatine,  298 

Gelatinised,  2J>9 

Gum,  298 

Manufacture,  283 

Properties,  284 

Safety,  284 

with  active  bases,  285 

with  inert  bases,  283 

Ebullioscope,  176 

Echinochrom,  137 

Effusiometer,  Bunsen's,  62 

Ehrlich's  side  chain  theory,  138 

Eicosane,  32 

Electrical  conductivity,  29 

Emulsin,  134 

Emulsor,  Kuhlmann,  278 

Enantiomorphism,  20 

Enantiotropy,  130 

Enzymes,  23,  133,  134 

Equilibrated  action,  136 

Synthetic  action,  136 
Epichlorhydrin,  258 
Erythrene,  109 
Erythritol,  109,  225 
Erythrodextrin,  141 
Esters,  124,  234 
Ethanal,  250 
Ethanamide,  421 
Ethanamidine,  426 
Ethandial,  393 
Ethandiol,  217 
Ethane,  24,  36 

Polychloro-derivatives  of,  122 
Ethanol,  130 
Ethene,  108 
Ethenol,  216 
Ether,  228 

Industrial  preparation,  230 

Petroleum,  37,  76 

Properties,  228 

Recovery  from  air,  231 

Tests,  232 

Uses,  231 
Ethers,  226 
Ethine,30,  111 
Ethyl,  30 

acetate,  395 

acetoacetate,  395,  396 

bromide,  115 

bromopropionate,  369 

carbonate,  431 

chloride,  115,  117 

chloracetoacetate,  397 

chlorocarbonate,  431 

chloroformate,  431 

cyanurate,  427 

diacetylsuccinate,  397 

diazoacetate,  385,  424 

dichloroacetoacetate,  397 

fluoride,  115,  117 

formate,  328,  395 

hydrosulphide,  233 

hydroxycrotonate,  394 

iodide,  115,  117 

isocyanate,  428 

isocyanurate,  428 

malonate,  368 
VOL.  II. 


Ethyl  methyl  ketone,  256 

mustard  oil,  430 

nitrate,  235 

nitrite,  235 

oxalate,  240 

peroxide,  232 
hydrate,  232 

phosphate,  234 

sodioacetoacetate,  396,  397 

sodiomalonate,  369 

sodiomethylmalonate,  369 

sulphate,  235 

sulphide,  234 

sulphite,  235 

sulphoxide,  234 

thioacetate,  419 

thiocyanate,  429 
Ethylacetamide,  420 
Ethylacetamido-chloride,  425 
Ethylacetimino-chloride,  425 
Ethylacetylene,  110 
Ethylamine,  241 

ethyldithiocarbamate,  434 

hydrochloride,  420 
Ethylcarbinol,  214 
Ethylcyanamide,  431 
Ethylene,  106,  108 

bromide,  118,  217 

chloride,  118 

cyanide,  256 

iodide,  118 

monothiohydrate,  257 

oxide,  256 

Polychloro-derivatives,  122 
Ethylenecyanohydrin,  256 
Ethylenediamine,  257 
Ethylhydrazine,  246 
Ethylidene  chloride,  118 
Ethylidene  compounds,  118 
Ethylideneacetone,  398 
Ethylidenecyanohydrin,  238,  256 
Ethylmagnesium  bromide,  243 
Ethylmercaptan,  233 
Ethylsulphone,  234 
Ethylurethane,  432 
Etiline,  122 
Eucaine,  119 
Excelsior  mill,  200,  269 
Exhausters,  53 
Explosion,  258 

by  influence,  265 

Determination  of,  264 

Heat  of,  259 

Pressure  of  gases,  261 

Velocity  of  combustion,  263 
projectiles,  317 
reaction,  263 

Volume  of  gases,  261 

wave,  262 

Explosive,  Favier's,  263,  304 
Explosives,  258 

Abel's  test  for,  314 

Analysis  of,  313 

Charging  density  of,  262 

Classification  of,  266 

Destruction  of  waste,  312 

Non-congealing,  274,  276 

Progressive,  263 

Safety,  35,  305 

Sensitiveness  of,  315 

Shattering,  263,  303 

Sprengel's,  304 

Stabilisation  of,  292 

Statistics  of,  319 

29 


450 


INDEX 


Explosives,  Storage  of,  312 
Theory  of,  259 
Uses  of,  318 

Fats,  Consistent,  90 

Dropping-point  of,  6 
Fehling's  solution,  255,  400 
Fermentation,  Alcoholic,  132,  145,  152,  204 

Lactic,  151,  387 
Fibrinogen,  137 
Firedamp,  34,  305 
Fishery  statistics,  69 
Fodder,  Molassic,  166 

Nutritive  value  of,  182 
Forcite,  298 
Formaldehyde,  247 
Formalin  (Formol),  Analysis  of,  247 
Formamide,  421 
Formates,  327 
Formhydrazide,  426 
Formins,  257 
Formolite  reaction,  71,  91 
Formula,  Constitutional,  15,  17 

Empirical,  13 

Structural,  15,  17 
Formulae,  Rational,  18 

Unitary,  15 
Formyl  chloride,  379 
Formyloxime  chloride,  427 
Francolite,  104 
Fruit  essences,  Artificial,  349 
Fulgurite,  284,  304 
Fuller's  earth,  80,  89 
Fulminate  of  mercury,  308 

Analysis  of,  308 
Fumaria  officinalis,  374 
Furfuraldehyde  (Furfural),  173 
Furnace,  Combustion,  8 

Gas,  45 

Fusel  oil,  109,  146,  165,  172 
Fuses,  309 

Bickford,  310 

Electric,  311 

Galalith,  250 
Gafezin,  191 
Gas,  Air,  60 

Blue,  58 

Illuminating,  38  et  seq* 

Marsh,  33 

meters,  56 

Oil,  65,  98 

producer,  45,  60 

Riche,  60 

Water,  58,  98 
Gases,  Permanent,  34 
Gasolene,  37,  76 
Gasometers,  54 
Gaultheria  procumbens,  127 
Gelatine,  Blasting,  285 

dynamites,  285,  298 
Gelignite,  298 
Geranial,  252 
Geraniol,  216,  252 
Gin,  190 

Glass,  Hardened,  94 
Glonoin,  275 
Glutarimide,  422 
Glyceraldehyde,  393 
Glycerides,  218 
Glycerol  (Glycerine),  36,  146,  217 

Industrial  preparation,  220 

Qualities  of,  223 

Refractive  index,  219 


Glycerol,  Statistics,  223 

Tests  for,  223 

Uses,  220 
Glycerose,  398 
Glyceryl  trinitrate,  258 
Glycine  (Glycocoll),  379,  385,  423 
Glycocyamidine,  435 
Glycocyamine,  434 
Glycogen,  137 
Glycol,  217 
Glycol  acetates,  256 

chlorohydrin,  256 

dinitrate,  256 

Ethyl  ethers  of,  256 

mercaptan,  257 
Glycollamide,  421 
Glycollic  aldehyde,  393 
Glycollide,  384 
Glycols,  216 

Propylene,  217 
Glycolsulphuric  acid,  256 
Glycosine,  393 
Glyoxal,  393 
Glyoxaline,  393 
Glyoxiline,  284 
Goudron,  99 
"  Grains,"  203 
Grape  must,  186 
Greek  fire,  266 
Green  naphtha,  102 

oil,  103 

Schweinfurth's,  348 
Grisounite,  307 
Guanamines,  434 
Guanidine,  434 

Amino  derivative  of,  434 

Diazo,  434 

nitrate,  434 

Nitro-derivative  of,  434 
Guanine,  436,  440 
Guncotton,  285 

Compression  of,  293 

Manufacture  of,  288 

Properties  of,  287 

Pulping  of,  292 

Stabilisation  of,  292 

Thomson  and  Nathan's  process  for,  290 

Uses  of,  293 
Gunpowder,  266 

Manufacture,  267 

Haemocyanin,  137 
Hsemoerythrin,  137 
Haemoglobin,  135 
Halides,  Acid,  377,  379 
Halogens,  Detection  of,  7 

Estimation  of,  12 
Hansena  fermentation  vessels,  208 
Hardened  glass,  94 
Heat  of  combustion,  25 

explosion,  259 

formation,  25 

of  explosives,  259 

neutralisation,  26 
Hedonal,  119 
Helianite,  328 
Heneicosane,  32 
Hentriacontane,  32,  37 
Henze  autoclaves,  143 
Heptachloropropane,  123 
Heptacosane,  32,  37 
Heptadecarte,  32 
Heptaldehyde,  251 
Heptane,  32,  37 


INDEX 


451 


Heracleum  giganteum,  127,  130,  215 

spondylium,  215 
Heterocyclic  compounds,  29 
Hexacetylmannitol,  224 
Hcxacontane,  32,  37 
Hexacosane,  32 
Hexadecane,  32 
Hexadione,  399 
Hexamethylbenzene,  111 
Hexaraethylene,  106 
Hexamethylenetetramine,  187,  248 
Hexandiine,  114 
Hexanes,  32,  37 
Hexanhexol,  225 
Hexanitroethane,  237 
Hexanol,  215 
Hexine,  110 
Holocaine,  119 
Homoasparagines,  425 
Homology,  24 
Hops,  193 

Decoction  of,  203 
Humulus  lupulus,  193 
Hydantoin,  433,  435 
Hydramine,  257 
Hydraulic  gas  main,  45 

press,  270 
Hydrazides,  426 
Hydrazodicarbonarnide,  434 
Hydrazones,  246 
Hydrocarbons,  29,  31 

of  petroleum,  71 

of  the  CnH2n-2  series,  109 

of  the  CnH2n-4  and  CnH2n-6  series,  114 

Saturated,  29,  31 

Unsaturated,  29,  106,  116 

with  triple  linkings,  1 10 
Hydrogen,  Estimation  of,  8 

Nascent,  33 

Tyoical  alcoholic,  124 
Hydrolysis,  125,  442 

Enzymic,  134 

Hydroxy-acids,  Higher,  389 
poly  basic,  419 

Polyvalent  dibasic,  399 
monobasic,  391 
tri basic,  411 

Saturated  monobasic,  383 

Unsaturated  monobasic,  389 
/3-Hydroxybutyraldehyde,  245 
Hydroxyethylamine,  257 

Hydroxyethyltrimethylammonium        hydrox- 
ide, 257 
Hydroxylamine,  235 

derivatives  of  acids,  427 
Hydroxymethyleneacetone,  396,  399 
Hydroxymethyleneketones,  399 
Hydroxynitriles,  238 
Hyphomycetes,  133,  155 
Hypnotics,  118 
Hypoxanthine,  436 

Ichthyoform,  104 
Ichthyol,  103 
Ichthyolsulphonates,  103 
Iditol,  226 
Illuminating  gas,  38 

Analysis  of,  60 

Calorific  value  of,  39,  61 

Composition  of,  40 

History  of,  38 

Lighting  power  of,  62 

meters,  56 

Physical  and  chemical  testing  of,  60 


Illuminating  gas.  Price  of,  58 

Properties  of,  40 

Purification  of,  45  et  seq. 

Separation  of  naphthalene  from,  46 

Statistics  of,  59 

Yield  of,  58 
Imides,  421 
Iminocarbamide,  434 
Iminocarbamideazide,  434 
Iminochlorides,  425 
Iminoethers,  420,  422 
Iminothioethers,  425 
Iminourea,  434 
Index  of  refraction,  27 
Injectors,  Korting,  53 
Invertase  (Invertin),  134 
lodoform,  121 

reaction,  Lieben's,  131 

Tests  for,  122 
lodopropane,  117 
lodourethane,  432 
Ironac,  328 
Isobutane,  37 
Isobutyl  iodide,  118 
Isobutylcarbinol,  126,  215 
Isobutyramide,  421 
Isocyanates,  427 
Isocyanides,  238 
Isocyclic  compounds,  29 
Isoleucine,  424 
Isology,  24 
Isomaltose,  136 
Isomelamine,  431 
Isomerides,  17 

Boiling-points  of,  25 

Melting-points  of,  25 

Metameric,  18 

Optical,  20 

Racemic,  21 
Isomerism,  15,  17 

Cis-  and  trans-,  22 

Space,  19 

Isonitriles,  237,  238,  240,  427 
Isonitrosoketones,  253,  398 
Isopentane,  37 
Isoprene,  109,  113 
Isopropyl  iodide,  116,  117 
Isopropylacetylene,  1 10 
Isovaleryl  chloride,  380 
Isuret,  427 
Ivory,  Artificial,  351 

Kephir,  139,  191 
Kerosene,  72 
Ketenes,  256 
Keto-aldehydes,  394,  399 
Ketoketenes,  256 
Ketones,  116,  124,  243,  252 

Strache's  estimation  of,  255 
Ketonimides,  243 
Ketoximes,  253 

Beckmann's  transposition  of,  253 
Kieselguhr,  275,  283 
Kirschwasser,  190 
Koji,  155 
Koumis,  191 
Kratites,  305 
Kummel,  191 

Laccase,  134 

Lactams,  423 

Lactases,  134 

Lactates,  388  ' 

Lactic  acid  bacillus.  145,  387 


452 

Lactides,  384 

Lactone,  Bromobutyric,  355 

Isocaproic,  357 
Lactones,  355,  377,  384 
Lactyl  chloride,  389 
Lager  beer,  203,  205 
Lamp,  Carcel,  62 

Hefner- Alteneck,  62 
Law  of  Dalton,  5 

Hess-Berthelot,  25 

of  refraction,  27 
Lead  plaster,  351 

Sugar  of,  347 
Leben,  191 
Lecithins,  258 
Lees,  Wine,  170,  402,  408 
Lemons,  Cultivation  of,  413 

Treatment  of,  414 
Leucine,  20,  424 
Leucocytes,  139 
Levulinaldehyde,  399 
Life,  Origin  of,  137 
Light,  Polarised,  27,  395 

Sources  of,  64 

Standards  of,  62 
Ligroin,  37,  76 
Limonene,  416 
Lipase,  134 
Liqueurs,  190 

Liquids,  Specific  gravity  of,  7 
Lithoclastite,  284 
Lupulin,  193,  203 
Lyddite,  303 
Lysine,  392,  424 
Lysins,  139 
Lysoform,  250 

Magnesia,  Effervescent,  413 
Magnetic  rotation,  28 
Maize,  142,  193 
Malamide,  421 
Malt,  141,  196 

Cleaning  of,  200 

Diastatic  power  of,  199 

Evaluation  of,  199 

Green,  196 

Grinding  of,  200 

Kilning  of,  198 

Mashing  of,  201 
Maltase,  134,  141 
Malting,  196 

Maltodextrinase,  134,  204 
Maltose,  134,  199 
Mammoth  pump,  278 
Manlianite,  305 
Manna,  225 
Mannatriose,  225 
Mannide,  226 
Mannitan,  226 
Mannitol,  225 

Hexacetyl,  224 

Hexanitro,  285 
Maraschino,  190 
Marmite,  149 
Marsala,  190 
Mashing  apparatus,  20 1 
Masut,  77,  86 
Medziankite,  305 
Melam,  431 
Melamine,  431 
Melene,  109 
Melibiase,  134 
Melinite,  303 
Melting-point,  5,  25 


INDEX 


Mercaptans,  233 
Mercaptide,  Mercuric,  233 

Sodium,  233 
Mercaptols,  252 
Mercury  fulminate,  308 
Mesityl  oxide,  253 
Mesitylene,  111 
Metaldehyde,  250 
Metalepsy,  15 
Metamerism,  18,  228 
Meters,  Alcohol,  173 

Automatic  gas,  58 

Dry  gas,  56 

Gas,  56 
Methanal,  247 
Methanamide,  421 
Methanamidoxime,  427 
Methane,  24,  33 

Derivatives  of,  31 

Industrial  uses  of,  35 

Preparation  of,  35 

Properties  of,  34 
Methanol,  127 
Methanthiol,  233 
Methene,  108 
Methenylamidoxime,  427 
Methoxymethane,  228 
Methyl,  30 

chloride,  ll(i 

cyanide,  238 

ether,  228 

iodide,  117 

isothiocyanate,  430 

mustard  oil,  430 

nonyl  ketone,  397 

sulphide,  233 
Methylacetylurea,  420 
Methylal,  251 
Methylamine,  240 

hydrochloride,  117,  241 
Methylbutanol,  215 
Methylcyanamide,  431 
Methylene,  108 

bromide,  115,  118 

chloride,  115,  118 

iodide,  115,  118 
Methylethylacetylene,  1 10 
Methylethylcarbinol,  214 
Methylglyoxal,  399 
Methylheptenone,  363 
Methylisopropylcarbinol,  12G 
Methylpropane,  37 
Methylpropanol,  215 
Methyluracil,  436 
Methylurethane,  426 
Microbes,  132 
Micrococci,  133 
Micron,  133 
Milk,  134 

Fermented,  191 
Molasses,  Beet,  166 
Molecular  volume,  25 
Monoacetin,  257 
Monoacylhydrazides,  426 
Monochlorhydrin,  257 
Mononitroglycerine,  274 
Morphine,  138 
Morphotropy,  24 
Moulds,  132 

Mucors,  133,  155,  156,  412 
Murexide,  436,  437 
Muscarine,  257 
Mustard,  Black,  430 

oils,  430 


INDEX 


453 


Muta-rotation,  28 
Mycoderma  aceti,  340,  341 

vini,  341 
Myristin,  350 

Naphtha,  65 

Naphthalene,  Estimation  in  coal-gas  61 

from  coal-gas,  46 
Naphthenes,  71 
Neradol,  250 
Neurine,  257 
Nisser  powder,  305 
Nitriles,  237,  427 
Nitroacetins,  274 
Nitrocellulose,  285 

Constitution  of,  286 
Nitrochlorhydrin,  274 
Nitro-derivatives,  235 
Nitroethane,  236,  237 
Nitroform,  237 
Nitroformins,  274 
Nitrogen,  Detection  of,  7 

Estimation  by  Dumas'  method,  10 
Kjeldabl's  method,  11 
Will  and  Varrentrapp's  method,  12 

Stereoisoinerism  of,  22 
Nitroglycerine,  275 

Filtration  of,  282 

Manufacture  of,  277 

Stabilisation  of,  281 

Uses  of,  282 
Nitroguanidine,  434 
Nitrohexane,  236 
Nitromethane,  237 
Nitropropane,  237 
Nitrosamines,  240 
Nitrostarch,  285 
Nitrourea,  432 
Nitrourethane,  432 
Nomenclature,  Official,  29 
Nonane,  32 
Nonodecane,  32 
Nonyl  aldehyde,  251 
Number,  Acetyl,  224,  225 

Acetyl  acid,  225 

Acetyl  saponification,  225 

Acid,  105 

Octadiene,  110 
Octane,  32 
Octocosane',  32 
Octodecane,  32 
Octylene,  109 
(Enanthaldehyde,  251 
(Enoxydase,  134 
Oil,  Acetone,  255 

Allyl  mustard,  430 

Castor,  390 

Ethyl  mustard,  430 

for  gas,  98 

Gelatinised  vaseline,  93 

Lemon,  415 

Methyl  mustard,  430 

Paraffin,  76 

Paraffin  wax,  94 

Propyl  mustard,  430 

Resin,  92 

Shale,  102 

Solar,  72,  98 

Turkey-red,  390 
Oil-gas,  64 
Oils,  Engine,  92 

Flash-point  of,  83,  91 

for  gas,  98 


Oils,  Heavy,  76 

Mineral  lubricating,  86 

Mustard,  430 

Spindle,  92 

Vaseline,  89 

Viscosity  of,  83,  90 
Olefines,  106 

Constitution  of,  108 

Nomenclature  of,  106 

Preparation  of,  107 

Table,  106 
Oleine,  358 
Opsonins,  139 
Optical  activity,  19,  69 

antipodes,  23 

properties,  26 

Organo-metallic  compounds,  242 
Ornithine,  392,  424 
Ortho-ethers,  324 
Orthoform,  119 
Oxalates,  368 
Oxamide,  421 
Oxidation,  Enzymic,  135 
Oximide,  422 

Oxy-acetylene  blowpipe,  113 
Oxydases,  134 
Oxygenases,  135 
Ozoform,  250 
Ozokerite,  31,  69,  94,  104 
Ozonides,  359 

Palmitates,  350 
Palmitin,  350 
Panclastite,  304 
Paracyanogen,  427 
Paraffin  wax,  94 

Analysis,  105 

Statistics,  106 
Paraffins,  29,  31 
Paraformaldehyde,  248 
Paraglobulin,  137 
Paraldehyde,  246 
Parthenogenesis,  Artificial,  138 
Partial  pressures,  5 
Pasteur  flasks,  147 
Pasteurisation,  186,  210 
Pastinaca  sativa,  130 
Penicillium  glaucum,  23 
Pentacosane,  32 
Pentadecane,  32 
Pentaerythritol,  225 
Pentahydroxypentane,  225 
Pentaline,  122 

Pentamethylenediamine,  257 
Pentanediene,  110 
Pentanes,  37 
Pentanol,  205 
Pentatricontane,  32 
Pentenes,  110 
Peptase,  134 
Peroxydases,  135 
Peroxyozonides,  356 
Petrinage,  299 
Petrolene,  99 
Petroleum,  65 

coke,  78 

Composition  of,  70 

Crude,  70 

Desulphurising  of,  80 

Distillation  of,  75,  76 

ether,  76,  86 

Extraction  of,  73 

Flash-point  of,  84 

fountains,  73 


454 


INDEX 


Petroleum,  History  of,  65 

Illuminating  power  of,  84 

Optical  activity  of,  69 

Origin  of,  67 

Pipe-lines  for,  75 

Properties  of,  70 

Purification  of,  78 

Refining  of,  78 

residues,  86 

Specific  gravity  of,  70,  72 

Statistics  of,  81 

tanks,  80 

Tests  for  lighting,  83 

Transport  of,  75 

Uses  of,  81 

Viscosity  of,  83 
Petroline,  76 
Pharaoh's  serpents,  429 
Phenylsuccinimide,  422 
Phlegm,  158 
Phorone,  256 
Phosgene,  118,  431 
Phosphines,  242 
Phosphorus,  Detection  of,  8 

Estimation  of,  13 
Photogen,  98 
Photometer,  Bunsen's,  63 

Lummer  and  Brodhun's,  63 
Phylloxera,  188 
Picoline,  252 
Pierrite,  305 
Pinacoline,  217 
Pinacones,  217 
Pinnoglobin,  137 
Piperazine,  257 
Piperidine,  1 10 
Piperylene,  110 
Pitch,  99 

Coal,  99 

Mineral,  99 

Plastering  of  wines,  187 
Platinichlorides,  14 
Polarimeters,  28 
Polarisation  of  light,  27 
Polyglycerines,  218 
Polymerism,  14 
Polymethylenes,  29 
Polymorphism,  24 
Potatoes,  Starch-content  of,  13,  141 
Powder  B,  296 

Black,  266 
Powders,  Brown  prismatic,  273 

Chlorate,  304 

Chocolate,  273 

Mining,  267 

Perchlorate,  304 

Prismatic,  272 

Prometheus,  304 

Smokeless,  295,  298,  300,  302,  303 

Smokeless  sporting,  267 

Sporting,  267 

Various,  311 
Precipitins,  139 
Pressed  yeast,  149 
Propaldehyde,  251 
Propane,  32 
Propanol,  214 
Propanone,  254 
Propantriol,  217 
Propargyl  aldehyde,  252 
Propene,  109 
Propenol,  216 
Propine,  110 
Propionamide,  421 


Propionyl  chloride,  380 
Propyl  iodide,  115 

mustard  oil,  430 
Propylcarbinol,  214 
Propylene,  109 
Propylpseudonitrile,  236 
Proteolytic  action,  134 
Protococcus  vulgaris,  225 
Protol,  218 
Protoplasm,  137 
Pseudoisomerism,  18,  394 
Ptomaines,  257 
Ptyalin,  134 

Purification  by  physical  methods,  '2 
Purine,  436 
Putrescine,  257 
Pyropissite,  95 
Pyroxyline,  285 
Pyrrole,  422 
Pyrrolidine,  422 
Pyrrolilene,  109 
Pyruvic  aldehyde,  399 

Racemisation,  23 

Rackarock,  304 

Radicles  and  types,  Theory  of,  1 5 

Reaction,  Baeyer's,  107 

Blank  and  Finkenbeiner's,  247 

Deniges',  413 

Formolite,  71 

Grignard's,  33,  243 

Kamarowsky's,  172 

Korner  and  Menozzi's,  375,  423 

Lieben's,  121,  129,  131 

Melsen's,  339 

Perkin's,  352 

Rimini's,  131,  172 

Sabatier  and  Sendcrens',  35,  67,  124 

Schiff's,  246 

Scudder  and  Riggs',  129 

Uffelman's,  386 

Yarrentrapp's,  350 

Wallach's,  357 
Reactions,  Reversible,  136 

Reversible  enzymic,  136 
Reagent,  Deniges',  413 

Schardinger's,  134 

Schiff's,  172 
Rectification,  3,  158 

of  alcohol,  158 
Rectifier,  Hempel,  3 

Perrier,  166 

Savalle,  159 
Reductases,  134 
Refraction  constant,  27 
Refractometer,  83 
Refrigerator  for  wort,  204 

Kentschel's,  144 
Rennet,  134,  138 
Rhigolene,  37 

Rhizoporus  oligosporus,  155 
Rhodinol,  358 
Rice,  193 

lUcho-Jialphen  test,  83 
Ricin,  138 
Robin,  138 

Robinia  pseudacacia,  138 
Roburite,  306,  307 
Rochelle  salt,  401 
Rubber,  Synthetic,  109,  113 
Rum,  190 

Saccharimeters,  28 
Saccharometer,  Balling,  153 


INDEX 


455 


Saccharomyces  cerevisirp,  134,  137,  145,  184 

Saccharomycetes,  133 

Saccharone,  410 

Salin,  183 

Salt  of  sorrel,  368 

Rochelle,  401 
Sanguemelassa,  166 
Saponification,  234 
Saponin,  138 
Sarcosine,  385,  423,  435 
Sawdust,  Utilisation  of,  333 
Scheelisation,  220 
Schists,  Bituminous,  100 
Schizomycetes,  132 
Schizosaccharomyces  Pombe,  204 
Schnapps,  190 
Schneiderite,  304J 
Scrubbers,  48 
Securite,  307 
Semicarbazide,  246,  433 
Semicarbazones,  246,  433 
Separators,  Naphthalene,  46 

Tar,  46 
Series,  Aliphatic,  29 

Ethylene,  106 

Fatty,  29 

Homologous,  24 

Isologous,  24 

Paraffin,  31 
Serine,  424 
Sero-therapy,  138 
Serum,  Physiological,  139 
Serum-albumin,  137 
Shale,  100 
Shalonka,  75 
Shimose,  303 
Siperite,  304 
Smokeless  powders,  295,  298,  302,  303 

Military,  300 
Soap,  350,  358 

Antiseptic,  79 
Sodium  acetonebisulphite,  253 

ethoxide,  131,  214 
Solanine,  138 
Solenite,  302 

Solubility  of  organic  compounds,  25 
Solvents,  Non-inflammable,  122 
Sorbitol,  226 
Sorbose  bacterium,  226 
Sorrel,  Salt  of,  368 
Specific  gravity,  25 

refraction,  27 

rotation,  28 
Spent  wash,  157,  182 
Sphserobacteria,  133 
Spirilla,  133 
Spirit,  Crude  wood,  128 

Denatured,  173,  176 

of  sweet  wine,  117 

of  wine,  130 

Purification  of,  172 

Wood,  128 

Spiritus  tetheris  nitrosi,  117 
Spirobacteria,  133 
Spores,  132 
Stachyose,  225 
Standard  scrubber,  48 
Staphyloooccus,  133,  151 
Starch,  133 

Estimation  of,  141 

Saccharification  of,  143 
Steam,  Superheated,  4,  77 
Stearine,  350 
Stereoisomerides,  Separation  of,  23 


Stereoisomerism,  19 

of  nitregen,  22,  253 
Stibines,  242 
Streptococci,  133 
Sublimation,  2 
Succinamide,  421 
Succinanil,  422 
Succinates,  366,  371 
Succinimide,  366,  421,  422,  436 
Sucrase,  134 
Sugar  of  lead,  346 
Sulphonal,  119,  233,  252 
Sulphones,  233 
Sulphonium  compounds,  233 
Sulphoricinate,  390 

Analysis  of,  391 
Sulphur,  Detection  of,  8 

Estimation  of,  13 
Superheated  steam,  4,  77 
Syntheses,  Asymmetric,  137 

Talitol,  226 
Tamping,  264 
Tanks,  Macdonald,  69 

Weiss,  69 
Tantiron,  328 
Tar,  Coal,  99 

Distillation  of,  88,  97 

Lignite,  96 

Mineral,  67 

Statistics,  100 

Statistics  of  lignite,  105 

Wood,  99 
Tartar,  402 

Analysis  of,  403 

Cantoni's  process,  405 

Cream  of,  401,  407 

emetic,  401 

Goldenberg's  process,  403 

industry,  402 

Statistics  of,  406 

Tarulli's  method,  404 
Tartrates,  401 
Tartrazine,  411 
Taurine,  257,  424 
Tautomerism,  18,  394 
Tea,  439 

Tension  theory  of  valency,  107 
Tetanolysin,  139 
Tetrabromoe  thane,  122 
Tetrachloroethane,  122 
Tetrachloromethane,  122 
Tetracosane,  32 
Tetradecane,  32 
Tetraline,  122 

Tetralkylphosphonium  hydroxide,  242 
Tetramethylarsonium  compounds,  242 
Tetramethylenediamine,  257 
Tetramethylmethane,  37 
Tetranitrodiglycerine,  218,  274 
Tetranitroethane,  237 
Tetranitromethane,  237 
Theine,  438 
Theobromine,  437 
Theophylline,  436 
Theory  of  explosives,  259 

fractional  distillation,  3 

radicles,  15 

substitution,  15 

types,  15 

valency,  Baeyer's  tension,  107,  366 
Thioacetamide,  238,  425 
Thioacids,  419 
Thioalcohols,  233 


456 


INDEX 


Thioaldehydes,  246 
Thioamides,  425 
Thioanhydrides,  419 
Thiocarbamide,  434 
Thiocyanates,  429 
Thioethers,  233 
Thioketones,  253 
Thiols,  233 
Thiophosgene,  433 
Thioserine,  424 
Thiourea,  434 
Thiourethane,  434 
Thyol,  104 
Tonsile,  104 
Toxins,  137 

Velocity  of  reaction  of,  139 
Trauzl's  lead  block,  316 
Trialkylphosphine  oxide,  242 
Trialkylphosphonium  hydroxide,  242 
Triazoformoxime,  428 
Trichloromethane,  118 
Trichloropurine,  436 
Tricosane,  32 
Tridecane,  32 
Trieline,  122 
Triethylamine,  241 
Triethylenediamine,  257 
Triethylsulphonium  hydroxide,  233 

iodide,  233 
Triformol,  248 

Trihydroxytriethylamine,  257 
Tri-iodomethane,  121 
Triketonamines,  252 
Trimethylacetyl  chloride,  380 
Trimethylamine,  117,  241 

hydrochloride,  117 
Trimethylbenzene,  111 
Trimethylcarbinol,  215 
Trimethylene,  106 
Trimethylmethane,  37 
Trimethylsulphonium  iodide,  234 
Trinitrocellulose,  286 
Trinitroglycerine,  258,  275 
Trinitromethane,  237 
Trinitrophenol,  303 
Trinitrotoluene,  304 
Triolein,  358 
Trional,  119 
Trioxymethylene,  248 
Tristearin,  220 
Trithioketones,  253 
Tryptase,  134 
Tumelina,  166 
Turkey-red,  391 

oil,  390 

Tyndall  phenomenon,  69 
Types,  Multiple,  16 

Theory  of,  16 
Tyrosinase,  138 

Undecane,  32 
Uramil,  437 
Urea,  1,  431,  432 

Alkyl  derivatives  of,  432 

nitrate,  432 

Nitro-derivative  of,  432 
Urease,  139 
Ureides,  433,  435 
Urethane,  432 


Uro-acids,  435 
Urotropine,  187,  248 

Valency,  16 

Tension  theory  of,  107 
Valeraldehyde,  251 
Vaporiraeter,  Geissler,  174 
Vaseline,  93 

Artificial,  93 

oil,  89 

Gelatinised,  93 
Velocity  of  esterification,  23 
Verdigris,  347,  348 
Vermouth,  190 
Veronal,  119 
Vigorite,  307 
Vinasse,  158,  188,  404 
Vinegar,  340 

Adulteration  of,  344 

Analysis  of,  344 

Artificial,  344 

German  process,  341 

Luxemburg  process,  342 

Malt,  344 

Michaelis  process,  342 

mite,  341 

Wine,  344 

worms,  341 

Viscometer,  Engler's,  90 
Vital  force,  1 

Waggon-still,  76 
Waterproof  fabrics,  346 
Wax,  Algse,  68 

Carnauba,  350 

Chinese,  216,  351 

Japanese  vegetable,  350 

Mineral,  94 

Montan,  95 

Paraffin,  94 
Westphalite,  306,  307 
Wetterdinamit,  284,  307 
Wheat,  193 
Wine,  184 

Alcohol-free,  185,  186 

Analysis  of,  188 

Statistics  of,  188 
Wood  charcoal,  268 

Distillation  of,  330 

spirit,  127,  128 

Poisoning  with,  128 

Xanthine,  436,  441 
Xanthogenamide,  434 
Xeroform,  122 
Xylitol,  225 
Xyloidin,  286 

Yeast,  134, 137,  140,  145,  149,  204 
Acclimatised,  151 
Frohberg,  204 
industry,  149 
Logos,  204 
Pressed,  149 
Pure,  147 
Saaz,  204 
Wild,  204 

Zinc  alkyls,  33,  243 

lactate,  388 
Zymase,  134,  139,  147 
Zymogen,  205 


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